United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600 7-79 143
June 1979
Research and Development
Design,
Fabrication and
Testing  of the
Air-Jet Oil Boom
Interagency
Energy/Environment
R&D Program
Report

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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology  Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

      1    Environmental  Health Effects Research
      2.   Environmental  Protection Technology
      3.   Ecological Research
      4.   Environmental  Monitoring
      5.   Socioeconomic Environmental Studies
      6.   Scientific  and Technical Assessment Reports (STAR)
      7   Interagency Energy-Environment Research and Development
      8.   "Special"  Reports
      9.   Miscellaneous Reports

This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND  DEVELOPMENT series. Reports in this series  result from the
effort funded  under  the 17-agency Federal  Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport  of energy-related pollutants and their health and ecological
effects; assessments of, and  development of, control technologies for energy
systems; and  integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                       EPA-600/7-79-1^3
                                       June 1979
       DESIGN, FABRICATION AND TESTING
           OF THE AIR-JET OIL BOOM
                     by

               Steven H. Cohen
            William T. Lindenmuth
         HYDRONAUTICS, Incorporated
           Laurel, Maryland 20810
           Contract No. 68-03-2497
               Project Officer

               John S. Farlow
  Oil and Hazardous Materials Spills Branch
Industrial Environmental Research Laboratory
          Edison, New Jersey 08817
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
     OFFICE OF RESEARCH AND DEVELOPMENT
    U.S.  ENVIRONMENTAL PROTECTION AGENCY
          CINCINNATI, OHIO ^5268

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                                 DISCLAIMER
     This report has been reviewed by the Industrial Environmental Research
Laboratory-Cincinnati, U.S. Environmental Protection Agency and approved
for publication.  Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection Agency,
nor does mention of trade names or conmercial products constitute endorse-
ment or recommendation for use, nor does the failure to mention or test
other conmerical products indicate that other conmercial products are not
available or cannot perform similarly well as those mentioned.

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                           FOREWORD
     When energy and material resources are extracted, processed,
converted, and used, the related pollutional impacts on our en-
vironment and even on our health often require that new and in-
creasingly more efficient pollution control methods be used.
The Industrial Environmental Research Laboratory - Cincinnati
(lERL-Ci) assists in developing and demonstrating new and im-
proved methodologies that will meet these needs both efficiently
and economically.

     This report describes performance evaluation tests of a re-
search prototype Air-Jet Boom.  The principle shows promise of
performing effectively at relatively high water current speeds,
thereby making spill cleanup possible' in currents that normally
cause conventional booms to fail.  This technique will be of
interest to all those concerned with cleaning up oil spills in
inland and coastal waters.  Further information may be obtained
through the Resource Extraction and Handling Division, Oil and
Hazardous Materials Spills Branch, Edison, New Jersey.
                         David G. Stephan
                             Director
           Industrial Environmental Research Laboratory
                            Cincinnati
                              111

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                            ABSTRACT


     This report describes the design, fabrication and testing
of the Air-Jet Boom; a novel boom which has the capability to
divert oil slicks under wave and current conditions that norm-
ally preclude the deployment of conventional booms.  Tests at the
EPA's OHMSETT facility have demonstrated that this boom can,  for
example, successfully divert oil slicks at 3 knots with 85, per-
cent efficiency when at 30 degrees to the flow.  Moreover, with
the addition of steep, 4-foot waves, the boom's performance is
virtually unchanged.

     The key operational feature is a continuous, horizontally
oriented air jet ejected from along the boom at the water's
surface.  The flow interaction and the ensuing momentum transfer
from the air jet to the water surface (by viscous and turbulent
shear stress) induce a strong local surface current just ahead
of the boom,  when the boom is deployed at an angle to the flow
(diversionary mode), the induced current causes the oncoming oil
slick to be deflected and transported across the water's surface
and apart from the clean, underlying flow.

     Overall, each boom module is about 33 feet long and 2 feet
in diameter.  Major components include two inflatable sections
(ducts) to support the continuous air-jet nozzle; and a center
support float/jet pump arrangement to supply the high-volume,
low-pressure (23,000 standard cubic feet/minute, at 3 inches of
water) air flow required for operation.  Some unique features of
the structural design are low draft (l inch) and excellent com-
pliance to waves.  Furthermore, the sections are both light-
weight and highly compactible for storage.

     This report was submitted in fulfillment of Contract No.
68-03-2497 by HYDRONAUTICS, Incorporated under the sponsorship
of the U. S. Environmental Protection Agency.  The report covers
a period from January 1977 to January 1978 and was completed as
of July 1978.
                               IV

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                           CONTENTS

Foreword	    ill
Abstract	„	    iv
Figures	   vii
Tables 	     x
Symbols and Abbreviations	    xi
Acknowledgments	xiii
     1.  Introduction	     1
     2.  Conclusions 	     6
     3.  Recommendations 	     7
     4.  Description 	     9
              General	     9
              Air Supply	     9
              Intended Use	    l4
              Rigging	    ill-
              Deployment 	    19
              Storage	    19
     5.  Development Program Summary 	    22
              Design and Fabrication 	    22
              OHMSETT Proof Tests	    22
              Modification 	    22
              OHMSETT Performance Tests	    23
     6.  Design and Fabrication	    24
              Inflatable Sections	    24
                  Functional Requirements	    24
                  Structural Analysis	    24
                  Wave Conformance	    25
                  Resonant Interactions	    25
                  Nozzle Design	    26
                  End Plate and Clamping Arrangement ....    26
                  Full Length Prototype	    30
              Jet Pump	    30
                  Functional Requirements	    30
                  Design	    33
                  Performance Tests	    33

                               v

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                      CONTENTS (continued)


              Support Float 	   33

                  Functional Requirements  	   33
                  Design and Assembly	36
                  Towing Tests	36

     7.  OHMSETT Proof Tests	38

              General Objectives	38

                  OHMSETT Description 	   38
                  Test Rigging	38
                  Test Variables	4l
                  Test Procedure	4l
                  Description of Tests	0  .  .   ^7
                  Summary of Results	50

     8.  Modifications	52

              Parameters Affecting Diversion Performance.  .  .   52
              Air-Jet Optimization	53
              Inflatable Section Modification 	   56
              Fairing Modification	56
              Support Float Modification	60
              Clamping Modification 	   60

     9.  OHMSETT Performance Tests	62

              General Objectives	62

                  Test Rigging	62
                  Test Variables	62
                  Test Procedure	62
                  Description of Tests	62
                  Summary of Results	73

    10.  Discussion of Results	76

              Calm Water	76
              Waves	76
              Reduced Power 	   8l

References	84

Appendices

     A.  Design Drawings	85
     B.  EPA Design Guidelines	97
     C.  Fabric Selection 	  101
     D.  Structural Analyses of the Inflatable Sections  .  .  .  105
                                VI

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                           FIGURES
Number                                                      Page
  la   Cross Section of a Conventional Oil Boom (Typical) „     2
  Ib   Deployment of a Conventional Oil Boom in Currents       2
       Greater Than One Knot (Typical)	
  2a   General Cross Section of Rigid Perforated Plate Boom    4
  2b   Proposed Deployment of Rigid Perforated Plate Boom .     4
   3   A View of the 10 Meter Long Air-Jet Boom	     5
   4   Schematic Cross Section of the Air-Jet Boom	    10
   5   Calm Water Test at OHMSETT	    11
  6a   Wave Conformance	    12
  6b   Bridging Between Waves 	    12
   7   Jet Pump Performance (Summary of Test Results) ...    13
   8   Proposed Deployment of the Air-Jet Boom	    15
   9   Proposed Deployment Alternative for the Air-Jet Boom
       Without Shore Access for the Air Compressor	    l6
  10   Rigging for the Air-Jet Boom	    17
 lla   Detail of Radius Cable and Fairing	    18
 lib   Detail of Snap Hook Bar	    18
  12   Rigging for Multiple Air-Jet Boom Deployment  ....    20
  13   Models of Preliminary Nozzle Configurations at
       Specified Operating Conditions .....  	    27
  l4   Velocity Profiles for Preliminary Nozzle Configura-
       tions	    28
 15a   Nozzle Structural and Aerodynamic Test 	    29
 15b   Nozzle Dead Load Test	    29
  16   Laboratory Demonstration of Prototype Inflatable
       Section in Still Water 	    31
  17   Schematic of the Jet Pump	    32
  18   Theoretical Jet Pump Characteristics	    34
  19   Jet Pump Performance Tests	    35
                               VIJ.

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                      Figures  (continued)

Number                                                     Page

  20   Support Float Towing Test--HYDRONAUTICS  Ship Model
       "D rf-i i—1 -n Vi                                                  "S /
21

22
23
24
25
26


27

28

29
30
31
^_J -1-
32
—/
33
34


A-l
A-2
A-3
A-4
A-5
B-l
C-l
Sketch of OHMSETT Towing Arrangement and Air-Jet

Air-Jet Boom Rigging for OHMSETT Proof Tests. . . .
End Plate "Blown-Off" of Inflatable Section ....
Leading Inflatable Section Folded at 4.5 Knots. . .
Test Sst-Up for Air-Jet Nozzle Optimization ....
Effect of Nozzle Height and Impingement Angle on
the Averaged Induced Current (Summary of Test
Results ) 	
Effect of Nozzle Throat Size on the Jet Momentum
and Boom Pressure for Constant Power 	
Effect of Nozzle Throat Size on Average Induced
Current (Summary of Test Results) 	
Air-Jet Boom Rigging for OHMSETT Performance Tests.
OHMSETT Performance Test Results (8 - 20°) 	
OHMSETT Performance Test Results (Q - 30°) 	
OHMSETT Performance Test Results (0 - 45° 	
Summary of OHMSETT Performance Test Results ....
Effect of Reduced Compressor Capacity on Diversion
Performance 	

HYDRONAUTICS., Incorporated Drawing No. 7705-001 . .
HYDRONAUTICS; Incorporated Drawing No. 7705-002 . .
HYDRONAUTICS j Incorporated Drawing No. 7705-003 . .
HYDRONAUTICS,, Incorporated Drawing No. 7705-004 . .
HYDRONAUTICS,, Incorporated Drawing No. 7705-005 . .
Proposed EPA Air-Jet Boom Cross Section 	
Dead Load Creep Tests (Summary of Results) 	
— ' i
39
40
49
49
54


55
-*'->'
57

58
.^
6l
77
1 1
78
(
79
( -X
80

RQ
u 0
86
88
90
92
94
98
-/ ^
103
                              vi ii

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                    Figures (continued)
Number                                                      Page
 D-l   Inflatable Section Under Uniformly Distributed
       Horizontal Load-Cantilever Support 	   107
 D-2   Inflatable Section Under Uniformly Distributed
       Horizontal Load-Cantilever with Simple End Sup-
       port 	109
 D-3   Inflatable Section Under Uniformly Distributed
       Moment-Cantilever Support	Ill
 D-4   Conformance of Inflatable Section in Waves of
       Long Wavelengths (>^\  cos 8)	Il4
 D-5   Conformance of Inflatable Section in Waves of
       Short Wavelengths (£•£].  cos 9)	117
 D-6a  Natural Frequency-Later Modes (undamped)  	   119
 D-6b  Natural Frequency-Torsional Modes (undamped)  ....   119
 D-7   Estimated Loads on Inflatable Section (Per Unit
       Length)	120
 D-8   Load/Deflection of Inflatable Section for  Deter-
       mining of Modulus of Elasticity	124
 D-9   Load/Deflection of Inflatable Section for  Deter-
       mining of Shear Modulus	125
                              IX

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                            TABLES

Number                                                      Page

   1   OHMSETT Proof Tests - May 1977	42

   2   Summary of Estimated Diversion During OHMSETT
       Proof Tests	51

   3   Summary of Nozzle Configurations 	   59

   4   OHMSETT Performance Tests - October 1977 	   63

   5   OHMSETT Performance Tests - November 1977	67

   6   Summary of Estimated Diversion During OHMSETT
       Performance Tests	74

  A-l  Design Drawings	0   85

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SYMBOLS AND ABBREVIATIONS
                                          2
A        cross  sectional  area,  in.2
A       projected area,  ft2
B       vibration coefficient, dimensionless
C-pj       drag coefficient,  dimensionless
c        conversion factor,  .036 pounds/inch2
D        drag,  aerodynamic,  pounds/foot
 a
D       drag, hydrodynamic, pounds/foot
E       modulus of elasticity, pounds/inch2
F       weight of end plate, pounds
f        thickness of the fabric,  inches
FT       lateral natural  frequency, undamped, cycles per  second
F™       torsional natural  frequency, undamped,  cycles per  second
G        gallons of oil distributed,  shear modulus, pounds/inch
g        gravitational constant, feet/second2
 \*t
h       height of the nozzle from the free  surface, inches
I       moment of inertia  of the  inflatable section, inches
J       polar  moment of  inertia,  inches 4
L        length of the boom, overall, feet
LA       lift,  aerodynamic,  pounds/foot
 Xl
Lp,       lift,  hydrodynamic, pounds/foot
-L       nozzle throat size, inches
ti       length of the inflatable  section, inches
M       nozzle reaction  moment, inch-pounds/foot
M        jet momentum, pounds/foot
m       uniform moment,  inch-pounds/foot
N       nozzle reaction  forces, pounds/foot
P        Jet pump inlet pressure,  pounds/inch2
p       internal boom air  pressure,  inches  of water
           XI

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Q       compressor flow, SCFM
q       air-jet flow, SCFM
r       radius of boom, inches
S       wetted area, feet
SCFM    standard cubic feet/minute
T       time of oil distribution, seconds
t       average slick thickness upstream, millimeters
t]_      local slick thickness at the boom, millimeters
U       maximum air velocity at the free surface,  feet/second
V       tow speed, current, feet/second
v       induced current velocity, feet/second
¥       weight per unit length, pound/feet
y       lateral deflection, inches
a       air-jet impingement angle, degrees
6       induced current depth, inches
p,      density, air, pounds/feet3
p^      density, fabric, ounces/yard2
 X1
p ;      density, water, pounds/feet3
cp       torsional deflection, radians
0       boom, deployment angle measured from'the 'direction
        of flow, degrees
CT       axial membrane stress, pounds/inch2      :
 a
a       circumferential membrane stress, pounds/inch
5       uniform vertical load, pounds/foot
uu       uniform horizontal load, pounds/foot
                       s
xii

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                        ACKNOWLEDGMENTS
     ¥e would like to extend our sincere thanks to John S.
Farlow, EPA Project Officer for his support and cooperation
throughout this work.  Our appreciation also goes to the en-
gineers, technicians and staff of OHMSETT for a fine job in
conducting the Proof and Performance Tests, especially Bob  Acker-
man, Hank Lichte, Mike Johnson, Sol Schwartz and Robert Dickson.
                              xiii

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                           SECTION 1

                          INTRODUCTION

BACKGROUND

     An important strategy in the control of an oil spill is
containment.  Without containment, oil will spread over large
distances, affecting areas well beyond the spill site.  Floating
oil booms, usually characterized by a vertical barrier extending
above and below the water surface, as shown in Figure la, are
routinely used for containment.  While conventional booms are
effective in calm water, experience shows that they do not work
well in fast currents or high waves.  Several investigators
studying the performance of conventional booms concluded that
oil loss increases quite rapidly with increasing currents greater
than approximately 1 knot, and wave action decreased this limit
further (132)*.

     Oil loss can be reduced, however, by angling booms into the
flow, thereby reducing the normal velocity component (relative
to the boom axis) below 1 knot.  In this configuration, booms do
not actually contain the oil, but rather redirect or divert the
flow of oil on the water surface apart from the clean bulk flow.
For example, when a spill occurs on a fast-moving river, oil can
be diverted to a quiescent area along the shoreline where it may
be recovered by suitable skimmers, as shown in Figure Ib.

     Performance testing of several commercially available booms
in the diversionary configuration at the Environmental Protection
Agency's Oil and Hazardous Materials Simulated Environmental Test
Tank (OHMSETT) has shown that the current for which there is no
loss may be increased from 1.0 knots to 1.6 knots (in calm water),
when a boom is deployed at 30 degrees to the flow (3).  With the
addition of 1-foot high regular waves with 1.5 second period,
the no-loss speed was reduced to about 0.5 knot.  Furthermore,
of all the booms tested, none could remain upright or stable
beyond a 2.0 knot current] containment failures occurred either
from.splashover or severe inclination from the vertical position
(planing or diving).
*Refer to References given on page 84,

                                1

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                                                  FLOTATION
                                               SKIRT
                                               BALLAST
     Figure la.  Cross section  of a conventional  oil  boom  ( typical )
SKIMMER
                         CONVENTIONAL BOOMS


                    VSIN9
SURFACE BUOY

       Figure Ib.   Deployment of a conventional oil boom in currents
                   greater than one knot (  typical )

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Advanced Concepts

     Because currents in excess of 2.0 knots are quite common on
inland waterways prone to oil spills (i.e., precluding the use
of conventional booms), the Environmental Protection Agency has
sponsored  several  studies to investigate and demonstrate the
feasibility of various high-current boom concepts.

     In one of the more recent studies, a rigid, perforated
plate, diversionary oil boom was developed and demonstrated (4).
In principle, the boom is a floating baffle arrangement which
slows down the surface flow, allowing oil to be contained and
recovered  in a quiescent area of the boom, as shown in Figure
2a.  Tests at OHMSETT demonstrated that the performance of the
rigid boom was markedly better than that of the conventional
booms.  The rigid boom is capable of diverting oil (1-milli-
meter slick) at 3-0 knots with less than 15 percent loss when
deployed at 45 degrees to the flow; but, as noted in the study,
use  of this boom should be limited to situations with wave
heights less than 1 foot.  Moreover, because of high drag forces
inherent in the concept and the sturdy moorings required, as
shown in Figure 2b, the boom is best suited for permanent de-
ployment at predetermined (i.e., high risk) locations.

     The present study, also sponsored by the Environmental
Protection Agency, resulted in the development of the Air-Jet
Boom; this is a unique diversionary device which relies on the
interaction of a high velocity air jet with the oil floating on
the  free surface.  The prototype boom is shown in Figure 3 with
a key for  the principle elements.  A detailed description of the
boom is presented in Section 4.

     Conclusions and Recommendations derived from the present
study follows in Sections 2 and 35 respectively.  Details of
the  development program, supporting design analyses, OHMSETT
proof tests and OHMSETT performance tests are described in
subsequent sections.  A discussion of results presented in Sec-
tion 10 concludes the report.
                               3

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FLOTATION
                   FLOW
                                                              V

                                                     PERFORATED
                                                       PLATE
                                          QUIESCENT AREA
                                       FOR OIL COLLECTION
        Figure   2a.   General cross  section of rigid perforated
                      plate boom (  from  Reference 4).
        RIGID, PERFORATED
           PLATE BOOMS
     (40-4'WIDE MODULES )
  SKIMMER
                         PILINGS & CABLES
     Figure   2b.  Proposed deployment of the rigid  perforated
                  plate boom (  from  Reference 4).

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A  -  INFLATABLE SECTIONS
B  -  CENTER SECTION
C  -  JET PUMP
D -  SUPPORT FLOAT
E -  COMPRESSOR AIR SUPPLY HOSE
F -  CONTINUOUS AIR JET NOZZLE
         Figure  3.  A view of the  10 meter long Air-Jet Boom.

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                           SECTION 2

                          CONCLUSIONS

     The Air-Jet Boom has the potential to provide an effective
means of controlling oil slicks on inland waterways under condi-
tions that normally preclude successful deployment of commerci-
ally available booms or other recently developed.prototypes.

     Performance tests at OHMSETT have shown that the Air-Jet
Boom is capable of diverting thin oil slicks (2 millimeter) in
3.0 knot currents with 15 percent loss when deployed at 30 de-
grees to the flow.  Moreover, the addition of waves has only a
nominal effect on performance; steep, irregular waves (up to 4,
feet high) increased losses by only 5 "to 10 percent compared to •
experience in calm water, and in some cases there was no per-
ceptible increase.                .,                             ;

     Additional operational features that; distinguish the Air--
Jet Boom from other booms are its shallow draft and low drag.
The shallow draft is significant in two ways:  first, floating.
debris is readily swept beneath the boom without snagging, and'" '
second, the boom can be deployed over shoals or in shallow   " ,  -
streams where conventional booms will not even float.  Low drag
means -that rigging and deployment is somewhat easier and that .  .'
the natural tendency to form a catenary planform shape., which   ',.
hinders diversion, performance with conventional booms, is less
pronounced.

     The Air-Jet _Boom features unique capabilities for diverting
oil spills in fast current^and waves.  It relies upon a shore-
based compressor to supply air, however,  which restricts'the
choice of .deployment sites' to those having reasonable road access
for the compressor(s).  Of course, skimming gear and recovered.
oil storage tanks have the same type of limitation, so a spill
recovery system using an Air-Jet Boom for slick diversion should
not be unduly handicapped in this regard.  Consideration should
also be given to the length of air-supply hose that will be
needed to reach from the compressor to the boom, as the pressure
drop in an excessively long hose will cause a falloff in boom
performance.
                                6

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Task 2  -
                           SECTION 3

                        REG OMMENDATIONS

     A single 10-meter length of the Air-Jet Boom was demonstra-
ted to be effective under simulated environmental conditions;
ultimately, several adjoining lengths of boom should be tested
in the field to confirm feasibility from a standpoint of practi-
cality and compatibility with other oil spill control equipment.
Prior to field demonstrations, however, two preliminary ta.sks
should be undertaken:

     Task 1  -  The prototype version of the boom should be re-
                designed with particular regard to developing  a
                lightweight, field deployable unit with improved
                hull form and simplified rigging for multiple-
                boom-length applications.  At least two, and
                preferably three, booms should be fabricated.

                The improved booms should be tested at OHMSETT
                to evaluate performance, seakeeping characteris-
                tics and/or limitations arising from multiple
                boom deployment.  Special attention should be
                given to:  the effect of slick thickening on
                performance of the downstream booms, and the
                optimum spacing and arrangement of adjacent
                booms, including the effect of staggering booms
                one behind another to improve diversion effi-
                ciency.

                Following OHMSETT tests, the booms should be
                demonstrated in the field under realistic oper-
                ating conditions using a real spill scenario.  A
                suitable location for deployment might be a
                shallow (2 to 3 feet), fast-moving river (2 to 3
                knots) less than a few hundred feet wide.

     Other developmental projects that should be considered con-
cern promising alternative uses and/or configurations of the Air-
Jet Boom.  One involves two booms deployed in a V-configuration
ahead of an oil recovery vessel (such as the high-speed U. S.
Coast Guard ZRV Skimmer) in order to concentrate the flow of oil
into the skimming area and, thereby, increase the effective width
of the system.  A deck-mounted blower could supply the required
air flow.  A second developmental project that should be con-
sidered is the use of alternate air-supply systems that greatly

                                7
Task 3  -

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reduce the boom's power requirements compared to the present
compressor/jet pump design.  One concept with high potential is
a boom-mounted blower that might be either gas-engine driven or
remotely by hydraulic power.
                               8

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                          SECTION 4

                         DESCRIPTION

GENERAL

     The Air-Jet Boom is shown in Figure 3 and is composed of
two inflatable sections that extend from a rigid center section,
a compressor-operated jet pump and its support float*.  A sig-
nificant feature is the continuous air-jet nozzle formed by the
inflatable and center sections.  The nozzle., oriented with the
free surface as indicated in Figure 4, directs a high velocity
jet of air flow at the air/water interface along the length of
the boom.  The resulting shear stress at the interface induces
a local surface current; when the boom is deployed at an angle
to the flow, a thin oncoming oil slick is deflected and trans-
ported by this current across the surface, apart from the under-
lying bulk flow of clean water„  The oil's trajectory is indi-
cated in Figure 5 where "complete" diversion is being affected
in calm (only small wind-waves) water.

     When the boom encounters waves, the induced surface current
is generally undiminished because the inflatable sections are
compliant and thus conform to the wave contours maintaining the
necessary air-jet orientation,,  Figure 6 illustrates how well
the inflatable section negotiates steep, 4-foot high (crest to
trough), irregular waves.  In some cases, however, the sections
do not conform and form a "bridge" across adjacent wave crests
(i.e., in short wavelength waves, see Figure 6b); the air jet
will retain a degree of effectiveness even though it is extended
from the free surface for a short period of time.**

Air Supply

     The low pressure, high volume of air flow that is required
for a single air-jet boom is delivered by means of a jet pump
which expands and augments the air flow supplied by a high pres-
sure air compressor.  To achieve the boom's rated performance, a
standard, 750 SCFM, commercial grade air compressor will deliver
about 23,000 SCFM at 3 inches of water (see Figure 7).  Smaller
compressors can be used, but with reduced diversion performance.
 *Design and assembly drawings are given in Appendix A.
**Results from the OHMSETT Performance Tests are summarized in
  Tables 4 and 5.

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a = IMPINGEMENT ANGLE, 20
I = NOZZLE THROAT, li"
h = NOZZLE HEIGHT, 4"
P = INTERNAL AIR PRESSURE 3" H2O
U = MAXIMUM JET VELOCITY, 120 fps
6 = BOOM DEPLOYMENT ANGLE
                                                              SURFACE CURRENT, v
                                                                        LOCUS OF ZERO
                                                                         NORMAL FLOW
                       DEFLECTED
                          OIL
                         SLICK
                                                                 \
      Figure 4.  Schematic cross  section of the Air Jet Boom.
 NORMAL COMPONENT OF
AMBIENT CURRENT,  VSIN9

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* Typical trajectories of oil  slick particles
       FIGURES.  Calm water test at OHMSETT
                  ( 1 .5 knot current,  9  = 45° ).
                         11

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   Figure  6a.   Wave conformance (OHMSETT),
Figure  6b.    Bridging  between waves (OHMSETT)
                     12

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    LLJ
    C£
    D_



    O

    u



I-  750
20
15
- 500
10
   -  250
                                            40
                                                  50
60
                            JET PUMP INLET PRESSURE, P, (psig)
        Figure 7.   Jet pump performance (Summary of test results)
                                  13

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     Particular advantages of the jet pump air supply are that
it is simple to operate, is reliable, and is easily maintained
because it has no moving parts; is inexpensive; and is light-
weight.  The compressor(s) and hose(s) that are needed to drive
the jet pump can be procured at the time of a spill from local
industrial contractors, government facilities or equipment
rental companies.  Significant cost savings may be realized with
this approach since the compressor does not have to be purchased
or maintained.

     A disadvantage of the jet pump system is that the air com-
pressor must be reasonably close to the boom.  For practical
purposes, the distance between the two should probably be no
more than a few hundred feet.  Other air-moving systems could be
adapted to the boom to obviate this limitation.  One concept is
to use a gas-engine driven blower mounted on the support float;
a 28 horsepower engine would be required for each 10-meter
length of boom.

Intended Use

     The Air-Jet Boom is intended for deployment on inland water-
ways such as rivers, streams or inlets with fast currents and/or
high waves.  The boom's low draft allows the minimum water depth
to be as shallow as 4 or 5 inches.

     One possible deployment scheme is shown in Figure 8 where
the Air-Jet Boom is used in conjunction with conventional booms
(for diversion in quiescent areas) and a stationary oil skimmer
for recovery.  Compressor(s) are located on the shore and air
hoses are led out to the jet pump.  In cases where the exten-
sion of air hoses is impractical, road access is a problem or
air-hose pressure drops are excessive.  A more complex deploy-
ment could be achieved using boats or barges to carry the com-
pressors, as shown in Figure 9.

Rigging

     The boom's rigging transfers applied loads (i.e., mainly
the support-float drag) to mooring cables or adjacent booms with-
out disrupting the wave conformance of the inflatable section.
Referring to Figure 10, the rigging is made of five cables:  one
main, two rear stays and two radius cables.  All are prefit and
attached by quick connecting/disconnecting snap hooks (Figures
lla and lib).  One important operational feature is that if the
inflatable sections buckle (see Figure 10, position 2) from high
impact loads or passing debris, the radius cable will slide along
the main cable to alleviate stress which otherwise might tear up
or pull off the inflatable section.  Air pressure restores the
shape when the load is released.

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                                              AIR COMPRESSOR
            FLOATING AIR HOSE
CONVENTIONAL
    BOOM
 (QUIESCENT
    FLOW
   REGION
                                                     BANK
            Figure  8.   Proposed deployment of the Air Jet Boom,
                                15

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                                                                       SURFACE BUOY
INTERCONNECTS
                  Figure 9.   Proposed deployment alternative for the Air-Jet Boom
                            without shore access for the air compressor

-------
                          AIR HOSE
                       CLAMP TO SUPPORT FLOAT
                                                                      RADIUS CABLE
GUIDE RAILS
                                                              MAIN CABLE
                                                                               POINT OF
                                                                               ATTACHMENT
-PEAR RING
                           Figure 10.   Rigging for the Air-Jet Boom.

-------
Figure  lla.   Detail of radius cable and fairing.
     Figure lib.   Detail of snap hook bar,
                      18

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     A rigging concept for two or more booms is proposed as
shown in Figure 12.

Deployment

     The deployment of the Air-Jet Boom is in some ways similar
to that of conventional booms.  The deployment suggested in Fig-
ure 8 could be accomplished as follows:
     1.
     2
     3
Storage
Set the main cable between any two points ;  for example,
between conventional booms and the shore or between a
skimmer and a surface buoy.  Ideally, the cable should
be about 1 foot above the water surface.

Tow the boom,, with the inflatable sections  folded on
top of the jet pump, to the center of the cable and
attach the snap hook bar (on the main cable) to the
guide rails on the center section of the boom.

Clip on the rear stays between the pear rings at each
end of the main cable to the respective attachment
rings on the support float*.

Tow the compressor hose out to the support  float.   Idle
the compressor to keep water out of the hose.  (Note:
Standard commercial 2-inch ID hose will float even when
partially filled.  Water in the hose will not damage
the boom.)  Make the air hose connection to the support
float; a hand-tight connection is sufficient.  An alter-
native would be to connect the hose on shore and tow
both the hose and the support float to the  main cable
together.

Signal to shore to increase the compressor  speed;  the
inflatable sections will begin to unfold with increased
compressor output.  With the sections fully or partially
inflated, clip the radius cables to the main cable.  Any
water located in the boom will be automatically purged
through ports in the end plates to complete the deploy-
ment.
     The inflatable sections, when deflated, can be folded into
a small, lightweight package about 8 inch by 8 inch by 40 inch,
weighing less than 20 pounds.  These sections can then be nested
*If two or more booms are deployed, the rear stays are connected
 to adjacent support floats, whereas the rear stays for the
 outermost boom are connected to the pear rings as shown in Fig-
 ure 10.

                              19

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ro
o
         INTERMEDIATE BOOM


            HIGH PRESSURE
              AIR FLOW
-AIR HOSE
TEE CONNECTION
CLIPS TO
REAR STAYS
END BOOM
                                              -MAIN CABLE CONNECTS BETWEEN
                                              SNAP HOOK BARS
                        Figure 12.   Rigging for multiple Air Jet Boom  deployment.

-------
into the area between the jet pump and support float.  Overall
dimensions of the stored unit are approximately 4 feet by lOf-
feet by 3-| feet high; it weighs a total of 380 pounds**.
**Because of the steel/wood/Fiberglas construction, the weight
  of the prototype is overly high.  A production-type version
  would be considerably lighter; possibly 150 pounds.


                               21

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                           SECTION 5

                  DEVELOPMENT PROGRAM SUMMARY


     The Air-Jet Boom concept was developed in four successive
tasks:
                1.  Design and Fabrication
                2.  OHMSETT Proof Test
                3.  Modification
                4.  OHMSETT Performance Tests

     A brief overview of each task is given below,  while details
are relegated to later sections of this report.

DESIGN AND FABRICATION

     Based on EPA design guidelines, a prototype version of the
Air-Jet Boom was designed and fabricated.  Section 6 describes
the technical approach, important design criteria and procedures
used for the design of the boom, including the inflatable sec-
tions,  jet pump and support float.

OHMSETT PROOF TESTS

     Proof tests to evaluate the performance of the Air-Jet Boom
prototype in waves and currents that might be encountered in a
real spill were conducted under controlled reproducible condi-
tions of the EPA's Oil and Hazardous Materials Simulated Environ-
mental Test Tank  (OHMSETT).  Test objectives were to determine
the intrinsic operational limitations of the air-jet concept,
and to discover whether there were any structural limitations
imposed by the design.  One conclusion of these tests (described
in detail in Section 7) was that when the angle between the boom
axis and flow Is 30 degrees, complete oil diversion was gener-
ally limited to currents below about 2.5 knots, whereas struc-
tural failures (i.e., folding of one boom leg) occurred between
4 and 5 knots.

MODIFICATION

     The objective of this task was to rectify the problems that
were disclosed by the Proof Tests.  Clearly, a primary goal was
to improve the boom's diversion performance in currents greater
than 2| knots.  Section 8 describes the general method of ap-
proach and a description of the modifications that were subse-

                               22

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quently made to the prototype boom.

OHMSETT PERFORMANCE TESTS

     Using the modified version of the Air-Jet Boom^ tests were
conducted at OHMSETT that were similar to the earlier Proof
Tests; however3 greater emphasis was placed on delineating the
performance limits over a wider range of operating conditions^
including smaller boom deployment  (diversion) angles and reduc-
ing compressed air supply.  The test results^, described in Sec-
tion 9j show that the limiting current for complete diversion
was increased (from 2^ knots) to 3 knots.  At the reduced de-
ployment angle (20 degrees)3 diversion could be achieved at
speeds up to 4 knots.
                               23

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                           SECTION 6

                    DESIGN AND FABRICATION


     The design of the Air-Jet Boom was based, at least in a
general way, on guidelines provided by the Environmental Pro-
tection Agency.  These guidelines are included in Appendix B.

     The following paragraphs describe the approach and method-
ology leading to the overall boom design and the designs for the
three principal components:  the inflatable fabric sections, the
jet pump and its support float.  In many areas, the final design
evolved after several sequential steps.

INFLATABLE SECTIONS

Functional Requirements

     The inflatable section serves both as a duct to distribute
the air flow and as a foundation to support the air-jet nozzle„
Specifically, the section must have appropriate structural
characteristics and ruggedness to withstand internally and ex-
ternally applied loads and to maintain the continuity and orien-
tation of the air jet both in calm water and in waves.  In addi-
tion, it should be compactable, and easy to fabricate, clean and
maintain.

Structural Analysis

     The inflatable section is a fabric cylinder supported by
internal air pressure and attached at one end to the boom's
center "T" section.  Considering ways in which this section can
fail, two types of failure may be defined:

     o  Structural Failure - a tearing or bursting of the fabric.

     o  Structural Instability - a severe distortion of the
        cylindrical formation without structural failure.

     Designing to prevent the first of the two types of failure
was straightforward since it amounted to selecting an appropri-
ate fabric.  The problem was further simplified because the
level of stress in this application was well below the strength
of most off-the-shelf fabrics used in the fabrication of oil
booms.  Appendix C describes the fabric selection criteria, prop-
erties of the selected fabric and some brief tests concerning


                               24

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joint efficiency (heat sealing) and rate of creep under steady
load.

     The second of the two failures, structural instability., is
especially important with respect to the performance of the boom;
large distortions will disrupt the continuity and/or orientation
of the air jet.  Consequently, an analysis (described in Appendix
D) was undertaken to anticipate the structural characteristics
of the inflated section and to disclose what type of additional
support (e.g., cables), if any, would best prevent structural
instabilities.  Two. general modes of instability were considered:

     o  Lateral Instability - causing the inflatable sections
        to buckle or fold under the action of applied lateral
        loads.
     o  Torsional Instability - causing the inflatable sections
        to rotate away from the proper air-jet angle under the
        action of applied moments.

     The analysis indicated that the inflatable sections require
additional support (i.e., in addition to the cantilever-type
attachment to the "T" section) to prevent lateral instability
(see Appendix D, Case l), and that a simple end support will be
sufficient to prevent this instability (see Appendix D, Case 2).
Moreover, we found that no additional support (e.g., an internal
helical spring) would be required to prevent torsional instabil-
ity  (Appendix D, Case 3).

Wave Conformance

     Wave conformance (i.e., deflection and/or buckling of the
inflatable section in the vertical direction) allows the air jet
to remain within reasonable proximity to the free surface.  Ap-
pendix D considers the ability of the section to conform under
two wave conditions.  One condition concerns waves with lengths
greater than the projected length of the section (X > ^ cos 8)
and, the other pertains to waves with lengths equal to or less
than the projected length of the section (X ^ ^ cos 0).  The
results indicated that conformance will probably not be a prob-
lem in the first case, while in the latter case (i.e., X =s £.,_ cos
9), "bridging" could occur between adjacent wave creses (see Fig-
ure 6).

Resonant Interactions

     Calculations of the inflatable section's natural frequen-
cies in lateral and torsional modes for the undamped case (Ap-
pendix D) demonstrated that resonant interactions will probably
not occur because the natural frequencies are high and there will
be significant damping of motions from interactions with the free
surface.


                               25

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Nozzle Design

     The air-jet nozzle is intended to provide a coherent air
jet directed at the desired impingement angle to the free sur-
face.  Besides achieving this in calm water, the nozzle must be
sufficiently flexible to bend with the inflatable sections, yet
maintain the air-jet coherence and orientation in waves.  Addi-
tionally, the nozzle must be compactable for storage and easy to
fabricate.

     Several designs were evaluated, including folding rigid noz-
zles, inserts into formed fabric sleeves, sewed or glued on noz-
zles and all-fabric nozzles.  Two concepts using all-fabric con-
struction were considered to be most suitable because of their
flexibility and continuity of the air-jet and ease of construc-
tion.  Preliminary models of these configurations are shown in
Figure 13.

     Tests were conducted with these models to compare the co-
herence and maximum, velocities of the air jet for 3/^~inch
throat at 3.25 inches of water pressure (see Appendix B, item 7).
The results given in Figure l4 indicate that the "external" de-
sign was preferable over the "internal" one.  Moreover, the ex-
ternal nozzle is judged to be superior from a structural stand-
point because it is more capable of transferring the membrane
stress across the nozzle gap without distorting the nozzle shape.
Hence, further tests of the external fabric nozzle concept were
conducted using a variable geometry assembly to determine the
optimum nozzle convergence angle.  Here, a 25-degree double angle
was found to be best,although the variations in conformahce were
not significant in a range from 15 to 60 degrees.

     A mockup of the prototype section (see Figure 15a) was built
with selected fabric to demonstrate the feasibility of construc-
tion, and was tested to confirm the aerodynamic performance of
the fabric nozzle.  These tests, in conjunction with dead load
tests (see Figure 15^), showed the nozzle to be generally satis-
factory, although some refinements in the construction technique
were required.  For instance, heat-sealed construction was aban-
doned in favor of a sewed construction (shown in Appendix A).
With sewed construction, a major advantage is direct attachment
between the substrates; this prevents delamination of the coating
and distortion of the nozzle shape, which was experienced with
the heat-sealed joints.

End Plate and Clamping Arrangement

     The end plate closes off the inflatable section and provides
a point of attachment for the radius cable connection described
previously (see Figures 10 and lla).  The end plate is a fabric-
covered plywood disc.  It is attached to the fabric cylinder by
means of a clamp, much like a hose clamp, encased in a vinyl tube

                                26

-------
Figure  13 -  Models of preliminary nozzle configurations at specified
            operating conditions (view from  inside boom ).
                               27

-------
p=3.25"H/
                 NOZZLE
                                    7" STATION
                                               10" STATION
                                                U = Maximum Velocity along
                                                        Centerline

PRELIMINARY DESIGN
(/•'
r/N*^^
I/ ^
( Internal )
/
/^^
( External )
MAXIMUM VELOCITY /JET WIDTH
AT NOZZLE
115 fps



1 1 6 fps


AT 7 INCH
STATION
76 fps
w = 2 inch


92 fps
w = 1 inch

AT 10 INCH
STATION
53 fps
w = 3 inch


72 fps
w = 2 inch

    Figure   14.  Velocity profiles for preliminary nozzle configurations

                                    28

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Figure  15a.   Nozzle structural  and aerodynamic test
        Fiqure  15b.   Nozzle dead load tests
                          29

-------
to prevent cutting or abrasion of the fabric.

     If the inflatable section should become filled with water
(e.g., when the boom is being deployed), it will blow out of a
small port located at the bottom of the end plate.  Air normally
bubbles out of the opening.  As long as there is some air pres-
sure in the boom, most water will be bailed out; however, to re-
move all water the pressure must be equal to at least 1 inch of
water (i.e., the approximate boom draft).  To prevent water from
reentering the port in high currents (due to dynamic head), a
cowl is provided over the port as shown in Figure A-3 (Appendix
A).

Full Length Prototype

     Based on the results of the structural analysis and the
nozzle design, a full-length inflatable section was built and
demonstrated.  The laboratory setup for the demonstration, shown
in Figure l6, included a variable output blower with flexible
duct to supply the air flow and a clear plexiglass and plate to
permit observation inside the section.

     The objectives of this phase in the development were to
check the cylinder's stability in bending and torsion, and any
tendency for vibrations or oscillations in the nonreinforced
structure, and to make sure of the orientation and uniformity of
the air jet along the length of the section.  Evaluations were
conducted at design pressure (3.25 inches of water) and off-
design conditions (2.65 and 3.85 inches of water).  In all, the
inflatable section performed as anticipated.  Velocity and pres-
sure surveys revealed that the air jet was uniform along the
length of the boom.  Vertical measurements between the nozzle
and free surface indicated minor twisting along the length of
the boom.  Moreover, with a total of l8 hours operating time,
the fabric nozzle demonstrated excellent dimensional stability.

JET PUMP

Functional Requirements

     The jet pump provides the low-pressure, high-volume flow
that is required to supply the air jet.  It consists of an array
of nine high-pressure nozzles, a constant area mixing chamber,
and a diffuser section as shown in Figure 17.  The nozzles are
fed high-pressure air (~ 750 SCFM @ 58 psi) from a (shore-based)
air compressor.  The nozzles discharge high-velocity jets into
the mixing chamber that entrain surrounding ambient air into the
bellmouth.  The ambient and high-pressure air is combined into a
moderage velocity, low-pressure flow in the mixing section.  The
diffuser then expands the flow, reducing the velocity and in-
creasing the pressure to the level that is required by the in-


                               30

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            A   INFLATABLE SECTION PROTOTYPE
            B   END PLATE
            C   SUPPLY AIR DUCT
            D   TEMPORARY SUPPORT CABLE
Figure  16.  Laboratory demonstration of prototype  inflatable
           section in still water.
                          31

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                             BELLMOUTH
00
ro
              HIGH
             PRESSURE
             NOZZLE
                                      ^CONSTANT AREA
                                       MIXING CHAMBER
                                                                                              P,Q
DIFFUSER SECTION
                                Figure 17.  Schematic  of the jet pump.

-------
flatable sections.  Note that there are no moving parts in the
jet pump.

Design

     The design of the jet is based on well-known principles
(see Reference 5).  The design point and some parametric rela-
tionships are shown in Figure lo.  Details of the jet pump de-
sign, including the downstream tee section and turning vane ar-
rangement (to supply two inflatable legs), may be found in Ap-
pendix A.

Performance Tests

     Tests conducted with two inflatable sections, as shown in
Figure 193 confirmed the predicted performance of the jet pump.
Measured velocities and pressure distributions were uniform along
both legs of the boom.  No flow instabilities or vibrations were
observed in the jet pump or inflatable sections.

SUPPORT FLOAT

Functional Requirements

     The support float carries the weight of the jet pump, turn-
ing vanes and center "T" section and, in addition, provides rota-
tional stability (about the boom axis) for the inflatable sections.
We set forth a list of general factors to consider in developing
the support float design:

     o  The support float must support the entire boom when the
        fabric sections are deflated and folded on top of the
        center section.  It must be sufficiently stable in this
        condition to allow it to be easily towed.

     o  The draft of the center T-section must match the draft
        of the (dewatered) inflatable sections when they are
        extended.

     o  It should remain sufficiently level in high currents
        and varying angles of attack to prevent marked changes
        in the orientation of the air jet with the free surface.

     o  It must have adequate reserve buoyancy, waterplane area
        and dynamic stability to survive expected sea states
        while maintaining the draft of the center T-section.

     o  It should be light in weight to insure low drag and
        ease of deployment, yet strong enough to withstand
        applied loads and rough handling.
                               33

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z


Q
N
N
O
z
*
 5
 O
       u

       Z
       UJ
   -   25 -
   -   20 - 900
   -   15
   -   10
LJ_

u



o





u
•^f

•^f

u


O
IX")
I/}
UJ
             O
             u
                    Q_



                    Q_
               - 200
         -  800
         -  700
          -  600
                         1000     1200     1400     1600     1800



                          HIGH PRESSURE NOZZLE EXIT VELOCITY (fps)



* NOTE: THE TOTAL NOZZLE AREA IS DISTRIBUTED BETWEEN NINE NOZZLES IN

        THE PRESENT DESIGN



           Figure  18.  Theoretical jet pump characteristics.
                                  34

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CO
en
                             Figure  19.   Jet pump performance tests  (results  are

                                          shown  in Figure  7).

-------
Design and Assembly

     Based on the above guidelines,, a catamaran-type hull was
initially selected because of its characteristically good sta-
bility when the boom is deflated.  The extended hull length con-
tributes to rotational stability to maintain the desired air-jet
orientation.

     Construction was a composite of light-gauge sheet metal
filled with expandable urethane foam to prevent loss of buoyancy,
Plywood supporting structure was used to connect the hull to the
jet pump*.  A key step in the assembly procedure was to set the
jet pump and center T-section on the hulls in still water using
a temporary wooden cradle.  The cradle was then cut away as re-
quired to adjust the T-section draft to match the draft of the
inflatable section (about one inch) while maintaining the sup-
port float at zero trim and heel angles.  The temporary cradle
was then used as templates to cut the permanent plywood support
structure.

Towing Tests

     After this assembly was completed, still water tests (in
the flume shown in Figure l6) were conducted to find the float's
longitudinal center of resistance.  Rigging eyes were then at-
tached as appropriate.  Brief towing tests were then conducted
in the HYDRONAUTICS Ship Model Basin (HSMB®) as shown in Figure
20.  From these tests we found that additional flotation was re-
quired at the aft end of the float.  A bottom plate joining the
two hulls was also added.  Even with these improvements, the-
float's stability was marginal in a 5-knot current at an angle
of 45 degrees.

     Returning the jet pump/support float to still water, the
nozzle on center T-section was located with respect to the free
surface.  This final alignment was important because the rigid
noz'zle is the "witness mark" for setting the inflatable sections
on the center T-section.
*The method of construction was chosen so that modifications
 could be made with minimal difficulty.


                              36

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co
                  Figure 20.   Support float towing towing tests  -  Hyclronautics  Ship  Model  Basin
                              (  HSMB ® ) .

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                           SECTION 7

                      OHMSETT PROOF TESTS

GENERAL OBJECTIVES

     Proof tests were conducted at the Environmental Protection
Agency's Oil and Hazardous Materials Simulated Environmental
Test Tank (OHMSETT) to evaluate the performance characteristics
of the Air-Jet Boom under environmental conditions which might
be encountered in an actual oil spill.  The conditions were var-
ied systematically to determine how the performance of the boom
is affected by current, waves and boom deployment angle, etc.

OHMSETT Description

     The test facility is a large, unsheltered towing tank speci-
fically intended for the testing and development of devices and
techniques for the control of oil and hazardous materials.  The
primary feature of the facility is the towing basin; overall
length 667 feet, 65 feet wide with a water depth of 8 feet.  The
towing arrangement shown in Figure 21 is comprised of a main and
(connected) auxiliary tow bridge capable of tow speeds up to 6-
knots.  Waves of predetermined lengths and heights can be gener-
ated by the hinged-flap wavemaker at the far end of the tank and
absorbed by a slat beach at the near end.

     The oil distribution system, located on the main bridge,
lays down oil slicks of controllable width and thickness in
front of the test device.  Major components of the system are
storage tanks, pumps, flow meters and distributed manifold with
movable oil-spreading nozzles (see Figure 21).  The location and
number of these nozzles controls the width of the slick and its
position relative to the test device.  The thickness of the slick
is controlled by the discharge rate of the pump.  In general,  the
maximum pumping capacity was about 600 gallons per minute, al-
though high viscosity oils reduce the maximum flow rate markedly.

Test Rigging

     As shown in Figures 21 and 22, the Air-Jet Boom was deploy-
ed between two tow points on the main and auxiliary bridges.  One
tow cable was connected between a load cell on the main bridge
and the left pear ring of the Air-Jet Boom, and the second cable
was attached to the right pear ring and to a ratchet hoist on the


                               38

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                                                  ..  DIRECTION
                                                  ••  OF TOW
                                           NOT TO SCALE
           A    MAIN TOW BRIDGE
           B    AUXILARY TOW BRIDGE
           C    INTERCONNECTING TRUSS
           D    OIL DISTRIBUTION MANIFOLD
           E    PUMPS AND FLOW METERS
           F    STORAGE TANKS
           G    INSTRUMENT AND PERSONNEL SHELTER
           H    TOW POINTS
           I     AIR BOOM WITH RIGGING
           J    AIR HOSE
           K    AIR COMPRESSOR
           L    PHOTO TOWER
Figure 21.  Sketch of OHMSETT towing  arrangement and Air Jet Boom
           rigging.

                          39

-------
-tr
o
                                 Figure  22. Air Jet Boom rigging for OHMSETT proof tests

                                             (note air hose connection to jet pump).

-------
auxiliary bridge.  The hoist takes up any slack in the rigging
and preloads the cables.  When placed under a tension of about
1000 pounds, as measured with the load cell, the main cable is
suspended approximately 1 foot above the free surface.

     The compressor, mounted on the auxiliary bridge, was con-
nected to the jet pump by a length of 2-inch ID compressor hose
as shown in Figure 22.  Instrument hoses were also supplied to
measure the air pressure at the inlet to the jet pump and the
pressure inside the boom.

Test Variables

     The planned test matrix included two boom deployment angles,
45 degrees and 30 degrees; two test oils_, Circo X (Heavy) and
Circo XXX (Light); and various tow speeds and sea states. Addi-
tional details concerning each test are included in Table 1.

Test Procedure

     Tests were usually conducted using the following procedure.
Variations from this procedure, necessary in some instances, are
given in the Description of Tests.

     1.  Check the air compressor for proper operation.
     2.  Record the time and weather conditions (air tempera-
         ture, water temperature, wind speed and wind direction).
     3.  Record the supply air pressure at the inlet to the jet
         pump and the internal boom pressure.

     4.  Clear the tank area of nonessential personnel.
     5.  Start the wavemaker, if required.
     6.  The Test Engineer takes his position in the intercon-
         necting truss above the boom.  (Note:  During the test
         run he will estimate the percentage of oil diverted.)

     7.  Accelerate the bridge to the predetermined tow speed.

     8.  When desired tow speed is reached, commence oil dis-
         tribution at the desired flow rate.

     9.  At the end of the test run, stop oil distribution
         and tow bridge.

    10.  Stop wavemaker.

    11 <,  Lower skimming bar, idle the air compressor and tow
         back to starting position, clearing oil from the tank
         surface.
    12.  Record tow speed, gallons distributed, time distributed
         and percentage diverted.  Make note of any observations
         during the test run.  Brief test personnel for next test,

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                           TABLE 1 .   OHMSETT PROOF TESTS        MAY 17, 1977 TO MAY 26, 19/7
1*
OHMSETT
Test No.

1-1

1R-1

2-1

3-1

26-1

27-1

28-1
r^
fo 28F-1

28R'-1


32-1

46-1

47-1

48-1

49-1

50-1

51-1

52-1
Tow Speed
Knots/FPS
1
1.69
1
1.69
2
3.38
4
6.76
1
1.69
2
3.38
3
5.07
3
5.07
3
5.07

1
1.69
2
3.38
2.5
4.23
1
1.69
2
3.38
2.5
4.23
3
5.07
1
1.69
2
Boom
Angle

30

30

30

30

30

30

30

30

30


30

30

30

30

30

30

30

30
3
Wai' 2
Condition

C

C

C

C

C

C

C

C

C


SR

SR

SR

MR

MR

MR

MR

LHC
4
Oil
Type

L

L

L

L

H

H

H

H

H


H

H

H

H

H

H

H

H
5 6 7
Calculated
Gallons Time Thickness
Distributed (Sec) (ma)

265.5

260.0

233.0

208.5

191.0

235.2

222.3

225.6

222.5


313.0

227.8

222.0

221.0

215-5

220.0

206.0

-

180 2.2

180 2.2

91 1-9

45 1.7

180 1.6

90 2.0

60 1.9

60 1.9

60 1.9


180 2.6

90 1.9

72 1.8

180 1.8

90 1.8

72 1.8

60 1.7

-
8 9,10
Estimated
Diversion
($) Comments

64

72

69

68

100

100

60

60

60


100

95

80

100

95

75

55


1) Pneumatic barrier used to
segregate the diverted oil for
measurement (see Fig. 21) )
interferred with the performance
of the Air Jet Boom.
2") Boom pressure raised from
3.25 to 3.85 in. of water.


1) Pneumatic barrier secured
diversion estimated by OHMSETT
Test Engineer for remaining
tests.


Rope supports aft end of jet
pump to prevent float sinking.
Additional floatation added to
aft end of float. Rope
removed.
Small regular waves have no
effect on performance.












Inflatable section blew off -
loose clamp.
                                                                                                                (Continued )
*Number  refers to no'tes at end  of the table.

-------
TABLE  1.  (Continued)
1*
OHMSETT
Test No.

52R-1

53-1

53R-1

54-1

35-1

36-1

37-1

55-1

56-1

57-1

55R-1

58-1

59-1

60-1

61-1

62-1

63-1

14-1
Tow Speed
Knots/FPS
1
1.69
2
3.38
2
3-38
2.5
4.23
1
1.69
2
3.38
2.5
4.23
4
6.76
4.5
7.61
5
8.45
4
6.76
1
1.69
2
3.38
1
1.69
2
3.38
1.5
2.54
1.5
2.54
1
1.69
2
Boom
Angle

30

30

30

30

45

45

45

45

45

45

45

45

45

45

45

45

45

45
3
Wave
Condition

LHC

LHC

LHC

LHC

C

C

C

C

C

C

C

LHC

LHC

MR

MR

MR

MR

C
4
0.11
Type

H

H

H

H

H

H

H

-

-

-

-

H

H

H

H

H

H

L
5 6 7
Calculated
Gallons Time Thickness
Distributed (Sec) (mm)

284.5 180 2.4

254.0 90 2.1

267.0 90 2.2

213.0 75 1.7

275.0 180 1.6

230.0 90 1.4

208.0 72 1.2

_

-

-

-

262.5 180 1.5

229.0 90 1.3

236.0 180 1.4

212.0 90 1.2

234.0 120 1.4

445.0 120 2.6

236.0 180 1.4
8 9,10
Estimated
Diversion
(%} Comments
Uneven oil distribution.
95

80

85

70
Boom angle changed to 45 degrees.
100

75

20
No oil. Leading boom leg folds in
half at 4 knots. At 4i to 5 knots
the aft section of the jet pump
sinks 'such that water enters bell-
mouth floods the boom.

-

-

95

75

100

60

85

75 Thicker oil slick.
Change to light oil.
100 (Continued)

-------
TABLE  1.  (Concluded)

OHMSETT
Test No.

15-1

16-1

64-1

65-1

66-1

67-1

68-1

69-1

70-1

71-1

72-1

73-1

73R-1

74-1

75-1

76-1
Tow Speed
Knots/FPS
2
3.38
1.5
2.54
1
1.69
2.5
4.23
1.5
2.54
1.5
2.54
1
1.69
2
3.38
1-5
2.54
1.0
1.69
2
3.38

-
1
1.69
1-5
2.54
2
3.38
2
3.38
2
Boom
Angle

45

45

45

45

45

45

45

45

45

45

45

45

45

45

45

45
3
Wave
Condition

C

C

MR

MR

MR

MR

LHC

LHC

LHC

C

C

HHC

HHC

HHC

HHC

HHC
4
Oil
Type

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L
567
Calculated
Gallons Time Thickness
Distributed (Sec) (mm)

204.5

256.0

246.0

203.0

212.0

138.0

293.0

-

-

260.0

230.0

199.5

205.0

200.0

234.0

265.0

90 1.2

120 1.5

180 1.4

90 1.2

120 1.2

120 0.8

180 1.7

-

-

180 1.5

90 1.4

88

180 1.2

120 1.2

90 1.4

90 1.6
8 9,10
Estimated
Diversion
(%} Comments

75

90

95

15

70
Thinner oil slicker.
85

95
Because of time limitations oil
was not skimmed off the tank.
Tests 69-1 and 70-1 indicated
good stability and diversion.
Sorbent chips added.
100
Sorbent chips added.
75
Speed increased from 1 knot to
2 knots.

100

90

50
Debris added.
eg ( Concluded )

-------
                             MOTES FOR TABLE 1

1.  The first number indicates the test number as planned in the matrix.   The letter
    R following the test number indicates a'repeat test.  Additional repeat tests are
    indicated by R1.  The last number (I) signifies the OHMSETT Proof Test.

2.  The boom angle is measured between the direction of the tow and the longitudinal
    boom axis(see Figure 21).

3.  Wave conditions are as follows:                        ,                      J

                                                  H       L       T

            C  -  calm                           0.0      °°       »

           SR  -  smajl regular      '            0.50'    75'     5.5 sec

           MR  -  medium regular                 0.75'    18'     1..9 sec

          LHC  -  light harbor chop              2.0' "Random" "Random"

          HHC  -  heavy harbor chop              4.0' "Random" "Randomtr

    In wave conditions SR and MR beaches are raised.  Tests start as soon as the first
    wave front passes the boom.  In wave condition LHC and HHC beaches are lowered.
    Tests start after wave generator operates for about 15 minutes.  In wave condition
    C beaches may-be raised or lowered.

4.  Oil types are as follows:

              H - Heavy Test Oil                           L - Light Oil

         Type:  Circo X               !           Type:   Circo XXXX
         Viscosity:  755.5 cst @ 70°F            Viscosity:  10.1 cst @ 72aF
         Specific Gravity:  .936                 .Specific Gravity:  .882
         Surface Tension:  35.5 dyns/cm          Surface Tension:  32.4 dyns/cm
         Interfacial Tension:  24.6 dyns/cm      Interfacial Tension':   11.9 dyns/cm
         Analysis Number (OHMSETT):  67          Analysis Number ('OHMSETT):  6l

5.  Gallons distributed is recorded from the flow totalizer on the main bridge.  The
    flow rate is controlled by the Oil Distribution Operator during the test run to
    insure that the total volume of oil (precalculated) is distributed in front of the
    boom.

-------
                                NOTES FOR TABLE 1.   ( Continued )

 6.  Time is the elapsed time of oil distribution recorded with a stop watch by the Oil
     Distribution Operator.

 7.  Calculated thickness is computed with the following equation:

                            .       4o.6 G   ,   N
                            ^0  = VTL sin 6 M

     where,
             G = gallons distributed
             V = velocity (fps)
             T => tinfe (seconds)
             L = boom length (32 feet)
             9 = boom angle (degrees)

     This relationship assumes that the slick is evenly distributed over a given area
     specified by the projected length of the boom (L sin 6) and the distance of the test
     run (VT).  In real conditions, however, the oil slick is not evenly distributed.
     Variations of thickness are caused by i)  changes in flow rate (see Note 5), and ii)
     the spreading characteristics of the oil from the distribution nozzles.

 8.  Diversion is determined by the OHMSETT Test Engineer based on his experience and
     judgment.  The-value indicates the portion of the total quantity of oil diverted
     beyond the trailing edge of the boom.

 9.  Weather Conditions During OHMSETT Proof Tests - Air temperatures averaged about 70°F
     during the test period, ranging from about a- high of 80 F to a low of 55°F.  The
     barometer was steady at about 29-7 inches of mercury and winds were light, averaging
     about 5 to 7 knots.  Tank water temperatures at the start of the testing was 67°F
     and steadily increased to 74°F toward the end of the period.

10.  Movies and Slides - Movies and slides of the Air-Jet Boom Proof Test may be obtained
     on request from:  John S. Far.low, Project Officer
                       Oil and Hazardous Materials Spill Branch
                       U. S. Environmental Protection Agency
                       Edison, New Jersey 08817                                (Continued)

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Description of Tests  (see Table 1)

     Tests 1-1 Through 3-1;

          Comparing observations with measurements of the per-
centage of oil diverted, it was apparent that surface currents
generated by the OHMSETT pneumatic barrier* interfered with the
performance of the Air-Jet Boom.  Several modifications to re-
duce the adverse surface current had little effect.  One modifi-
cation., for instance, was to tow a deflection plate under the
boom so that it was directly over the barrier, thus blocking the
rise of air bubbles near the trailing edge of the boom.

          In subsequent tests,  the diversion was  estimated by
the Test Engineer.  While this method was somewhat subjective**,
it proved to be effective from  the standpoint that many more
tests  could be conducted during the test period since the time-
consuming process of  recovering the diverted oil  for volume mea-
surement was no longer required.

          Because of  poor performance at the design pressure
(3.25 inches of water),  the boom's pressure was raised to the maxi-
mum pressure (3.85 inches of water) that could be attained with
the air compressor  (750 SCFM at 58 PSI).  Remaining tests were
conducted at this pressure.

     Tests  26-1 and  27-
           It was  observed that  100 percent  of  encountered oil
 was  diverted, whereas  in  Test 2-1 (with the pneumatic barrier
 operating), only 69 percent diversion was measured.

      Tests 28-1 through 28R'-1;

           The aft end  of  the support float  submerged at  3 knots ;
 however,  the boom was  still operable.  In Test 28R-1, a  rope was
 added to  hold up  the support float.  Eventually, the rope was re-
 moved and additional flotation was cut to shape and taped to the
 aft  end of the float.   The flotation survived  the remaining tests.
   ^Normally  used  to  segregate  diverted  from undiverted oil in
    diversionary  boom  tests.
  **It  should be noted  that  independent,  estimated values of di-
    version by as  many  as  three  experienced OHMSETT observers were
    correlated to  within 5 percent as long as the losses did not
    exceed 25 percent.  When oil losses  became  excessive, the dis-
    crepancies were greater.  As a rule  of thumb, estimated values
    of  diversion below  50  percent are probably  only accurate to
    within 15 or 20 percent.
***Test numbers are  based on the planned matrix.

-------
     Tests 32-1, ^6-1 and ^7-1:

          Small regular waves (SR were observed to have little
effect on boom performance.  No further tests were conducted at
this sea state.

     Tests 48-1 through 31-1:

          Medium regular waves (MR) had a marginal effect on
boom performance.  As compared to Test 27-1, Test 48-1 indicated
only a 5 percent reduction in performance.

          During Test 52-1, the inflatable section blew off
while waiting for the light harbor chop (LHC) to develop (see
Figure 23).   An inspection revealed that the clamp had loosened.
Diversion in the light harbor (Test 53R-1) was 10 percent less
than in the medium regular waves (Test 51-1) and 15 percent less
than in calm water (Test 27-1).

     Tests 35-1 through 37-1:

          With the boom deployed at 45 degrees to the flow, di-
version decreased significantly.   Compared to Test 27-lj, the
boom at 45 degrees diverted about 25 percent less.  At 2.5 knots
(Test 37-1):? "the boom diverted very little oil.

     Tests 55-1 through 57-1:

          During Test 56-1, the leading inflatable section of
the boom was unstable, folding in half near the end of the test
run (see Figure 24).   The problem was probably caused by the
dynamic pressure associated with a bow wave at the leading edge,
coupled with increased skin friction drag along the length of
the inflatable section.  At 4f knots (Test 47-1), the support
float submerged so that water drawn into the jet-pump bellmouth
partially flooded the boom.  When the speed was subsequently re-
duced, the inflatable sections bailed the water and reinflated
in approximately a minute.  No damage was indicated.

     Tests 58-1 through 62-1:

          In a light harbor chop, the boom (deployed at 45 de-
grees) diverted as well in waves as in calm water (Test 36-1). .
In medium regular waves (Test 6l-l), however, performance was
reduced by 15 percent.

     Tests 14-1 through l6-l:

          Changed to light oil.  A comparison of Test 36-1 with
Test 15-1 indicates that there is little change in performance
    to differences in the heavy oil and the light oil,


                               48

-------
  Figure  23. End plate "blown off" of inflatable  section,
Figure  24.   Leading  inflatable  section  folded at five knots
                            49

-------
      Tests 64-1 through 67-!;

           These tests, compared with Tests 60-1 through 62-1,
indicate that in medium regular waves, heavy oil may be diverted
more effectively than light oil.  This may be due to a greater
tendency for light oil to break up with agitation.

      Tests 68-1 through 70-1:

           A comparison of Test 68-1 with Test 58-1 indicates
that oil type does not seem to affect oil diversion.  Because of
time limitations, Tests 69-! and 70-1 were conducted using the
oil from Test 68-1, which was distributed randomly over the
water surface.  Hence, estimates of diversion could not be made;
however, seakeeping and performance, in general, seemed good.
At the highest speed (Test 69-!), the diversion with light oil
did not appear to be as great as with heavy oil under comparable
conditions.

      Tests 71-1 and 72-1:

            Oil soaked urethane  foam sorbent chips were broad-
cast on the oil slick in front of the device to demonstrate the
feasibility of using the Air-Jet Boom in conjunction with skim-
mers using the sorbent chip principle.  At two knots, all chips
were diverted even though only 75 percent of the oil was diverted.
The projected "sail" area of the chip above the free surface
could have been responsible.  Chip diversion at higher speeds
(>2 knots) is probably effective.

      Tests 73-1 through 76-!:

           Final tests were conducted with the heavy harbor chop.
Comparing Test 7^-1 with Test l6-l, estimated diversion was
equivalent to that in calm water.  Debris added to  the oil slick
during Test 76-! caused no problem.  In most cases, debris was
blown away by the air-jet or drifted under the inflatable section
without snagging.

Summary of Results

      The test results,  with regard to diversion performance,
are summarized in Table 2.  Some general observations are:

      1.  The boom diverted 80 percent of the oil at speeds up
          to 2-| knots in calm water when the boom was deployed
          at 30 degrees to the flow.

      2.  Reduced performance is obtained when the  boom was
          deployed at 45 degrees to the flow.

      3.  At all boom deployment angles, waves caused little
          change in performance.

                              50

-------
    Oil-laden sorbent foam chips (Seaward cubes) were
    diverted without loss at 2 knots.
5.  Various types of debris, including shipping pallets,
    4-inch by 4-inch timber with nails and partially-
    filled 5-gaH°n cans, cleared the boom without snag-
    ging or damage.

6.  The leading inflatable section folded in half, as
    shown in Figure 24, at speeds between 4 and 5 knots.
    This was probably due to high drag forces on the
    blunt leading edge.

7.  At speeds in excess of 4.5 knots, the aft end of the
    support float submerged, causing water to be drawn
    into the jet pump, ultimately flooding the boom.
    When the speed was reduced below 4 knots, the sec-
    tions fully reinflated in about a minute.

  TABLE 2. SUMMARY OF ESTIMATED DIVERSION DURING
               OHMSETT PROOF TESTS
Boom Angle
30 degrees
(~2-mm slick)

45 degrees
(~1.5-iran slick)

Speed
(Knots)
2.0
2.5
3.0
1.0
1.5
2.0
Diversion (Estimated)
Calm
Water
100$
80$
60$
100$
90$
75$
Regular
Waves (MR)
95$
75$
55$
95$
70$
60$
Harbor
Chop (LHC)
85$
70$
-
95$
75$
                       51

-------
                             SECTION 8            :

                           MODIFICATIONS

 SCOPE          -                •    -

     The OHMSETT Proof Test demonstrated that the Air-Jet Boom is
 structurally stable in currents up to 4 knots.   At higher speeds,
 there were tendencies for. the leading inflatable section to fold
 and for the support float to submerge;'but very little diversion
 was achieved in currents  beyond :2.5 knot's.  Consequently, in
 terms of modifications to the boom,, resolving the high-speed
 structural problems was felt to be less important than improving
 the diversion performance.

 Parameters Affecting Diversion Performance

     Observations  made during the' OHMSETT Proof  Tests  indicated
 that., diversion was  related to the free  surface  flow induced by
 the air jet over a  region upstream'of the free  surface trough,
 as shown in Figure  4*.  The important flow parameters are the
 mean velocity of  the" induced flow (v) and its depth (6).  To ob-
 tain effective diversion:   the induced  velocity must  be at least
 equal to or .greater thafi the vector ;component of tow  speed (V),
 normal to the boom  (i.e.,  v S; ..V sin 6); and the ..momentum of the
 induced flow must be at least equal to  or greater than the,oppos-
 ing momentum of the approaching oil slick.

     Improvements  in diversion performance can be expected if the
 values of v and 6 are increased such that the momentum associated
 with the induced  flow is  increased**.  Increasing both the air-jet
 size and velocity would,  obviously, bolster the free  surfa-ce flow;
 but since the air-jet design was assumed to be  power  limited
 (i.e., fixed compressor capacity), the  problem  became one of op-
 timizing the existing air-jet nozzle configuration with regard to
 its momentum and/or the efficiency of momentum  transfer to the
 surface flow.  Parameters  that were considered  for alteration in-
 cluded:  the nozzle impingement angle (oc); nozzle height from the
 *This is in contrast to the mechanism described by previous in-
  vestigators (6)  who suggest diversion is more directly related
  to the influence of the free surface trough.

**Momentum is directly proportional to v and 6.

                               52

-------
free surface  (h); and the nozzle throat size  (£).  A brief de-
scription of  the experiments is given below.

Air-Jet Optimization

     Test Setup:

          The air-jet optimization tests were conducted in a
long, 2-foot wide tank., as  shown in Figure 25.  A variable
geometry air-jet nozzle assembly was mounted at one end of the
tank so that  the induced flow would be directed toward the op-
posite end*.  The induced velocity flow was determined by mea-
suring elapsed  time1 of travel for spherical floats  (specific
gravity = 0.95) between a ma'rk at the' free surface  trough and
marks at 6  feet, 8 feet., 10 feet, and 20 feet down  the .length of
the tank.   The .depth of the,induced flow, which is more diffi-
cult to determine, was reckoned using various size  floats (i.e.,
1/4, 1/33 and 3/4 inch diameters).

     Test Results:

          Tests were conducted with a fixed nozzle  throat (£ =
3/4 inch) for ten combinations of h, and a, including the exist-
ing configuration (h = 5 inch, a = 45 degrees).  For each con-
figuration, tests were run  for three different diameter floats
arid repeated  three times for each diameter.

          The averaged velocity  (normalized by the  result for
the existing  configuration) is plotted in Figure 26 as a func-
tion of impingement angle with the nozzle height as a parameter.
A 'simple analysis helps give perspective to these..test data.

          Intuitively, the  induced flow''should, be dependent on
the tangential  component of the  jet velocity (u) at 'its point of
impact on the surface, u cos a, where ,'u is 'a- function of the
distance from the jet nozzle ~Uf(x).  For-a' two-dimensional jet
in an infinite  medium, f (x)'cc x~n,. where n is', about. 1/2.  Hence,
we may approximate the normalized surface current as a., -function
of a and h  (= x sin a):               '..,  . : -           •>• .,
                      -cc  COS
•^Because  of  time  and  cost  restraints,  not  all  parameters  could
  be  considered.   In particular,  the  setup  does not account for
  the effects of tow" speed, V ,  or  deployment angle (8  = 90 de-
  grees).  Moreover, because  the tank is  closed, test runs had to
  be  brief to limit  recirculating flow.   Nevertheless,  the ex-
  periment, while  simplified  in  many  ways,  lent some insight into
  the comparative  importance  of  the nozzle  parameters.

                               53

-------
Ul
          12"
 VARIABLE GEOMETRY
  AIR-JET NOZZLE
    ASSEMBLY

	A
                                                                          a

                                                                          I

                                                                          h
                                                                               RANGE

                                                                                0° to 60°
                                                            ill L  O"
                                                            4  to Z
                                                         -  0" to 7"

                                                         -  0"to5"ofH2O
                                                                  FLEXIBLE
                                                                  AIR DUCT
  AIR
 FROM
BLOWER
                                           80'
                           Figure 25.  Test setup for air-jet nozzle optimization,

-------
O
O
LLJ


§
01
O_
z
LLJ
U
&L
LLJ
Q_
      100
       80
       60
       40
       20
         0
                     NOTE: v  = v AT a = 45 ,

                            h = 5",  I =  3/4"
 10
 O    h=4"

 A    h=5"

 D    h = 6"
                                                                                   EXISTING
                                                                                   NOZZLE

                                                                               CONFIGURATION
                                                                                I	I
20                  30


  NOZZLE IMPINGEMENT ANGLE  ( a )
40
                Figure 26.
Effect of nozzle  height and impingement angle  on  the average

induced current.   (Summary of test results).

-------
This indicates that an optimum impingement angle would -be around
35 degrees and that -h should be minimized (to bring the point of
impingement, close to the nozzle exit).

     The measured currents  show improvement with decreased h  (on
the order of .h"'?)-.  'Also, an optimum impingement angle does .exi^t,
but it is found to be on the order of.. 20 degrees-;  the' simple
analysis above does not account for the efficiency of momentum  !
transfer or the fact that the jet momentum is conserved a-
mend that a new set of inflatable sections be fabricated with
this throat size (1-^ inch).  However, because of the lower mar-
gin of structural stability with the 1^ inch nozzle, a second-  ;
set of inflatable sections'was also fabricated with the 3/4 inch
nozzle (h - 4 inch, cc = 20  degrees) which offers improved sta-
bility.  Comparisons would  then be made between the two modified
nozzle configurations (see  Table 3) during the OHMSETT Perform-
ance Tests with regard to diversion efficiency and stability.

Fairing Modification

     To limit folding of the inflatable section at high speed, a
fairing (shown in Figure .lla) was, .added to reduce  the drag co-
efficient of the otherwise  blunt end of the inflatable section.

                               56

-------
Ol
          O
          O
          00
          Q
          z
          12
          o
          CL.
Z)
I—
7.
LLJ


O
            O
              CM
            X
            u_

            9
            00
            LU
            I
            u
            z
                      00
                      OO
                      LU
                      &.
                      Q_



                      O

                      o
                      CO
                            0
                                                             FOR CONSTANT AIR-JET POWER
                            0.5
1.0,      1.5        2.0  . .    .2.5.


 -  NQZZLE THROAT (:*.), INCHES
3.0
                 Figure  27.
                   Effect of nozzle.throat size on  the  jet  momentum  and  boom

                   pressure for constant power.

-------
Oi

CO
            10
       o
       o
LJJ



O
        U
        Di
                                      NOTE: v0^v AT -6 = 3/4"


                                            0=20°, h =4"
        _ EXISTING	

           NOZZLE

         CONFIGURATION
                              3/4
                                                                 A
                                         1                1 1/4


                                   NOZZLE THROAT SIZE, I, (INCHES)
                                                                                  A
1  1/2
                        figure  28.  Effect of nozzle throat size on average induced current.

                                   (Summary of test results).

-------
          TABLE 3.   SUMMARY OF NOZZLE  CONFIGURATIONS














Nozzle
Designation
3/4" _ 45°
(existing)
3/4" - 20°
(modified)
(modified)
+
^-^
CM fn
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3.85
3.00

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H
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CD ?H
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45

20
20


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H ^1
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3/4

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3
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CD
O
£H tl
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•H g

fn O
CD CH
K* ^"1
•H CD
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1

2
3
Constant air horsepower per foot of boom.
1-leastj 2-betterj 3-best.
                             59

-------
Fiberglas-covered foam construction was used to reduce weight.

     Other solutions to prevent folding, such as shock cords or
cables, were considered unsuitable because stress transferred to
the fabric could cause tearing or hinder wave conformance.

Support Float Modification

     Additional reserve flotation was installed to prevent sub-
mergence of the support float at high speed*.  The center area
between the two hulls was filled, with,foam and covered with
sheet metal.  More flotation was also added at the aft end of
the support float, as shown in Figure 29.  Weights were placed
in the forward- end" of"; the "support" float-to compensate-for the
change in trim.  A clamping arrangement was also fitted to allow
attachment of 'the air , supply hose' so that it was free floating,
as shown in Figure 29.

Clamping Modification,

     A small lip, shown in Figure A-4 in.Appendix A, was added
to improve the' attachment of the fabric to the1 cehter section
and end plate.         :   •
*This approach is more of a stop-gap measure than a real solu-
 tion, since the problem concerns hull design.
                               60

-------
Figure  29.    Air jet boom rigging for OHMSETT performance tests
              (fJote  air  hose  connection  to  jet pump).

-------
                           SECTION 9

                   OHMSETT PERFORMANCE TESTS

GENERAL OBJECTIVES

     The general objective of the OHMSETT Performance Tests was
to evaluate the performance characteristics of the modified Air-
Jet Boom under a wider and more severe range of operating condi-
tions than encountered during the OHMSETT Proof Tests.

Test Rigging

     The rigging of the Air-Jet Boom for the Performance Tests
was nearly the same as it was for the earlier Proof Tests.  The
high-pressure air hose was connected directly to the jet pump
so that the hose was free floating (see Figure 29).  The air
compressor was from a different manufacturer; however, it was
equal in rated capacity and pressure.

Test Variables
     The test matrix included three boom deployment angles, 45
degrees, 30 degrees, and 20 degrees; two types of .test oil,
Circo X (Heavy) and Circo XXXX (Light); and various tow speeds
and sea states, including the 4-foot harbor chop.  In a few
tests, air pressure inside the boom was reduced to establish its
effect on performance characteristics.  Additional details con-
cerning the tests, including the properties of the test oil and
the weather conditions during the test, are given in Table 4.

Test Procedures

     Procedures used for the Performance Tests are the same as
outlined in Section 7.  Variations from this routine are de-
scribed in the Description of Tests.

Description of Tests

     Data from the Performance Tests is given in Tables 4 and 5. A
brief description of the tests (in chronological order) is given
below:

     Tests 1-2 through 9-2:



                               62

-------
                                          TABLE 4.  OHMSETT PERFORMANCE TESTS
                                         October 5, 1977 to October 13, 1977

1*
OHMSETT
Test No.
1-2

4-2

5-2

6-2

7-2

8-2

8A-2
O
CO
9-2

10-2

11-2

12-2

13-2

14-2

15-2

15A-2

16-2

17-2
Tow Speed
Knots/FPS
0-6
0-10.14
1
1.69
2
3.38
1.5
2.51*
2
3.38
1.5
2.54
1
1.69
1.5
2.54
1.0
1.69
2
3.38
1.5
2.54
2
3.38
1.5
2.54
1.5
2.54
1.5
2.54
1.5
2.54
2
3.38
2
Boom
Angle
45

45

45

45

45

45

45

"5

45

45

45

45

45

45

45

30

30
3
Wave
Condition
C

C

C

C

C

HHC

HHC

MR

C

C

C

C

MR

HHC

HHC

C

C
4567
Calculated
Oil Gallons Time Thickness
Type Distributed (Sec) (mm)
_

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H
_

294

265

240

131

201

266

264

244

264

273

132

251

237

147

328

234
_

180

90

120

90

90

180

120

180

90

120

90

120

120

120

120

90
_

1.7

1.6

1.4

0.8

1.6

1.6

1.6

1.4

1.6

1.6

0.8

1.5

1.4

0.9

2.7

1.9
8 9,10
Estimated
Diversion
(%} Comments
Tests 1-2 through 9-2 conducted
with 3/4"-20° nozzle.

100
Uneven oil distribution.
60
Trace loss.
100

75

75
Trace loss.
100

75
Changed inflatable section to
100 l£"-20° nozzle.

70
Trace loss.
100

90

80

80

90
Remaining tests conducted with
100 l£"-20° nozzle.
Trace loss.
100
»Number refers to notes at end of the table.                                                               (Continued)

-------
TABLE 4.   (Continued)

1*
OHMSETT
Test No.

18-2

18A-2

19-2

19A-2

20-2

46-2

47-2

31-2

32-2

33-2

,34-2

34A-2

35-2

35R-2

35A-2

36-2

37-2 -
2 3
Tow Speed Boom Wave
Knots/FPS Angle Condition
2.5
4.23
3
5.07
2
3.38
3
5-07
2
3.38
1.0
-1.69
2.0
-3.38
1.5
2.54
2.5
4.23
3.0
5.07
2.0
3.38
3
5.07
"2.0
3.38
2.0
3-38
3.0
5.07
1.5
2.54
2
' 3.38

30

30

30

30

30

30

30

30

30

30

30

- 30

30

30

30

30

45'-

C

c

HHC

HHC

MR

C

-, c

c

c

c

MR

HHC

HHC

HHC

C

C

C
4567
Calculated
Oil Gallons Time Thickness
Type Distributed (Sec) (mm)

H

H

H

H

H

H

H

L

L

L

L

L

L

L

L •-

L

- L-

232

232

270

,111

219

698

348

221

217

98

219

115

224

220

111

218

246

72

60

120

60

90

180

90

121

72

60

90

60

: - 90

90

60

120

- 90

1.9

1.9

1.7

1.9

1.8

5.8

2.9

1.8

1.8

0.8

1.8

1.0

1.9

1.8

0.9

1.8

1.-4
8 9,10
Estimated
Diversion
($) Comments

90

75

90

80

95
Thicker oil slick.
95
Thicker oil slick.
,95

100
Uneven oil distribution.
70

70

60
Leading inflatable section
folded in half.

70

80
Uneven oil -distribution.
60 - .- - -
Trace loss.
100

75 (Continued)

-------
                                                                TABLE 4.   (Continued)
Ui
OHMSETT
Test No.

38-2

3&R-2

39-2

39A-2

40-2

40A-2

48-2

48R-2

49-2

50-2

50A-2

51-?
52-2

53-2 	

54-2

32R-2

32A-2
Tow Speed
Knots/FPS
'2'
3.38
2
3.38
1.5
2.54
1
1.69
1.5
2.54
1.5
2.54
2
3.38
2
3.38
3
5.07
4
6.76
4.5
7.61
1
1.64
3.38
4
6.76
3
5-07
2,5
4.23
2.5
4.23
Boom
Angle

t-5

45

45

45

45

45

30

30

30

30

30

30
30

30

30

30

30
-3-
Wave
Condition

C

C

HHC

HHC

MR

MR

C

C

C

C

C

C
C

• c

C

C

C
-4-5; 6 - 7 - 8 9.10
Calculated Estimated
Oil Gallons Time Thickness Diversion
Type Distributed (Sec) (mm) (%} Comments

L

L

L

L

L

L

L

L

L

L

L

L
L

L

L

-L

L

122

219

266

116

229

126

224

265

217

213

118

598
348

227

231

271

204

.90

90

120.

180

120

120

90

90

60

45

40

180
90

45

60

80

75

0.7

1.3

1.6

0.7

1.3

0.7

1.9

2.2

1.8

1.8

1.0

5.0
2.9

•1.9 	

1.9

- 2.0

2.2
Variable diversion thin slick.
90
Uneven oil distribution.
60

60
Trace loss.
100

70

80

100

95

80

50

30

100
90

60 -

80

80
12' wide slick aligned with
100 trailing edge of boom, trace
                                                                                                         loss.                    ,..   .    , .
                                                                                                                                  (Continued )

-------
                                                                   TABLE 4.     (Concluded )
o
1*
OHMSETT
Test No.

55-2

56-2


57-2


57A-2

56A-2

49A-2


58-2

58A-2

58B-2

59-2

59A-2

59B-2

60-2
61-2
Tow Speed
Knots/FPS
2.5
4.23
3.5
5.92

4
6.76

4
6.76
3-5
5.92
3
5-07

1
1.69
1
1.69
1
1.69
1.5
2.54$
1.5
2.54
1.5
2.5t
1.5
2.54
3
5-07
2
Boom
Angle

30

30


30


30

30

30


30

30

30

30

30

30

30
30
3^567
Calculated
Wave Oil Gallons Time Thickness
Condition Type Distributed (Sec) (mm)

C L 147

C L 110


C L 92


C L 94

C L 110

C L 208


C L 358

C L 358

C L 358

C L 240

C L 240

C L 240

C L 240
C L 208

75

53


45


45

53

60


180

180

180

120

120

120

120
60

3.1

2.2


2.0


2.0

2.3

2.1


3.0

3.0

3.0

2.0

2.0

2.0

2.0
1.7
8 9,10
Estimated
Diversion
(%} Comments

100

100


100


60.

65

90


100

100

70

100

80

50

100
85
6' wide slick aligned with
trailing edge of boom, no loss.
6' wide slick aligned with
trailing edge of boom, trace
loss.
6' wide slick aligned with
trailing edge of boom, trace
loss.
6' wide slick aligned with
leading edge of boom.
6' wise slick aligned with
leading edge of boom.
12' wide slick aligned with
trailing edge of boom - see
test 49-2.
Supply pressure reduced to
24 psi.
Supply pressure reduced to
11 psi.
Supply pressure reduced to
1 psi.
Trace loss.

Supply pressure reduced to
20 psi.
Supply pressure reduced to
7 psi.
Debris added.

(Concluded )

-------
                                                            TABLES.  OHMSETT PERFORMANCE TESTS
                                                             NOVEMBER 2, 1977 TO NOVEMBER 10, 1977
XJ

1*
OHMSETT
Test No.
1-3
2-3
3-3
4-3
5-3
6-3
7-3
8-3
9-3
10-3
11-3
12-3
13-3
14-3
15-3
16-3
17-3
Tow Speed
Knots/FPS
1.5
2.54
2.0
3.38
3.0
5.07
4.0
6.76
2.0
3-38
2.0
3.38
3.0
5-07
3.0
5-07
4.0
6.76
1.5
2.0
3.38
3.0
5-07
4.0
6.76
2.5
4.23
2.5
4.23
3.0
5.07
3.0
5.07
2
Boom
Angle
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
3
Wave
Condition
C
C
C
C
C
HHC
HHC
MR
MR
C
C
C
C
C
MR
MR
HHC
4567
Calculated
Oil Gallons Time Thickness
Type Distributed (Sec) (mm)
H
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
243
230
202
220
468
241
260
270
_
218
234
224
265
439
230
234
258
120
90
60
45
90
90
60
60
..
120
90
60
45
72
72
60
61
3.0
2.8
2.5
2.7
5.7
3.0
3.2
3.3
-3.0
2.7
2.9
2.7
3.2
5.4
2.8
2.9
3.1
8 9,10
Estimated
Diversion
(%) Comments
100
Trace loss,
100
90
70
90
90
80
90
Data not recorded.
70
100
Trace loss.
100
90
Support float submerged.
80
Trace loss.
100
85
YC (Continued )

-------
TABLES.  (CONCLUDED)

1*
OHMSETT
Test No.
18-3

19-3

20-3

21-3

22-3

23-3

24-3
o
nn
00 25-3

26-3

27-3

28-3

29-3

30-3

31-3

32-3

33-3

34-3

35-3
2
Tow Speed, Boom
. Knots/FPS Angle
2.0
3.38
1.0
1.69
1.0
1.69
1.0
1.69
3.0
5.07
3.o
5.07
3.0
5.07
3.0
5.07
3.0
5.03"
2.0
3.38
2.0
3.38
2.0
3.38-
2.0
3.38

-
2.0
3.38
2.0
3.38
2.0 '
3.38
3.0
5.07
20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20
3
Wave
Condition
HHC

C

C

C

C

C

C

C

C

C

C

C

HHC

HHC

MR

MR

MR

MR
4
Oil
Type
L

L

L

L

L

L

L

L

L

L

L

L

L

L

; L

L

L

L
567
Calculated
Gallons Time Thickness
Distributed (Sec) (mm)
233

456 '

343

276

199

233

209

125

224

232

239

228

240

-

227

230

230

122
90

192

181

219

58

60

60

35

60

91

90

90

90

-

90

90

9Q-

60
2.8

5.2

4.2

2.8

2.5

2.8"

2.6

2.6

2.7

2.8

2.9

2.8

2.9

-

2.8 .

2.8

2 »'O .
1 ••••;• -.
1.5
8
Estimated
Diversion
(*)
80

100

•100

100

85

80

80

-

50

100

85

80

70

-
-_ .
100

90

-. 50

85
9,10
Comments

Nov. 7 - Winds 20-25 knots and
heavy rain - tests resumed
Nov. 9.
Supply
27 psi.
Supply
10 psi,
Supply
5 psi,
Supply
35 psi.
Supply
25 psi.
Supply
20 psi.
Supp ly
10 psi,
Supply
15 psi.
Supply
25 psi.
Supp ly
10 psi.
Supply
5 psi.
Supply
35 psi.
Supp ly
25 psi,
Supply-
35 psi,
Supply
10 psi.
-Supply
5 psi.
Supply
25 psi.
pressure reduced

pressure reduced
trace loss.
pressure reduced
trace loss.
pressure reduced

pressure reduced

pressure reduced

pressure reduced
to

to

to

to

to

to

to
leading leg folded.
pressure reduced

pressure reduced

to

to

presure reduced to

pressure reduced

pressure reduced

pressure reduced
end plate pulled
pressure reduced
trace loss.
pressure reduced

pressure reduced

pressure reduced
(Concluded )

to

to

to
off.
to

to

to ,

to


-------
                                               NOTES FOR TABLES 4 AND 5
-O
           2.


           3.
The first number indicates the test number as planned in the original test matrix.
The letter R indicates a repeated test.  The letters A, B, C, etc. indicates a vari-
ation of the preceding test.  The last number (2 or 3) signifies, that the test is
•from the OHMSETT Performance Tests.

The boom angle is measured between the direction of tow and the longitudinal boom
axis (see Figure 21).
Wave conditions are as follows:


        C  -  calm

       MR  -  medium regular 1

      HHC  -  heavy"harbor chop
                                                                H        L

                                                               0.0

                                                               0.75'    18'
                                                               4.00' ''random"
5.5 sec
"random"
               For wave condition,  MR,  the  beaches  are   raised.  Tests start after the wave
               generator operates for about 8 minutes.  (This makes the waves somewhat higher and
               steeper than the MR wave condition for the Proof Tests.)  For w-ave conditions LHC
               and HI1C beaches are lowered.  Tests start after the wave generator operates for about
               15 minutes.  For condition  C beaches may be raised or lowered.
               Oil types are as follows:

                         H - Heavy Test Oil

                   Type:  Circo X
                   Viscosity:  893 cst @ 70 F
                   Specific Gravity:   .938
                   Surface Tension:  36.0 dynes/cm
                   Interfacial Tension:  15.4 dynes/cm
                   Analysis Number (OHMSETT):  409
                                                       L - Light Test Oil

                                               Type:  Circo XXXX
                                               Viscosity:  15.4 cst @ 70 F
                                               Specific Gravity:  .899
                                               Surface Tension:  30.9 dynes/cm
                                               Interfacial Tension:   l4.3 dynes/cm
                                               Analysis Number (OHMSETT):  4l6
               Gallons distributed is recorded from the flow totalizer on the main bridge.  The flow
               rate is controlled by the .Oil Distribution Operator during the test run to insure the
               total volume of oil (precalculated) is distributed in front of the boom.   (Continued)

-------
                                    NOTES FOR TABLE 4 AND 5 .  ( Concluded )

            6.  Time is the elapsed time of oil  distribution recorded with a stop watch by the Oil
                Distribution Operator.

            7.  Calculated thickness is computed with the following equation:
                where,
                        G = gallons distributed
                        V = velocity  (fpsl
                        T = time  (seconds)
                        L = boom  length  (38 feet)
                        6 = boom  angle (degrees).

                This relationship assumes the slick is distributed over a given area specified by
                the projected length  of  the boom (L sin 9) and the distance of the test run (VT).
                In real conditions , however , the oil slick is not evenly distributed.  Variations
o               of thickness are  caused  by i) changes in flow rate (see Note 5}, and ii) the
                spreading characteristics of oil from the distribution nozzles to the water sur-
                face (see Figure  29).

            8.  Estimated diversion is determined by the OHMSETT Test Engineer based on his experi-
                ence and judgment.  The  value indicates the portion of the total quantity of oil
                diverted beyond the trailing edge of the boom.

            9.  Weather Conditions during OHMSETT Performance Tests - The weather was generally
                chilly.  Air temperature averaged about 50 F during the tests ranging from a high
                of 62 F to a low  of 48°F.  During some tests oil in the tow bridge storage tanks
                was heated to get proper flow rate and distribution on the free surface.  The barom-
                eter was steady and winds were light averaging 0-5 knots.  Tank water temperature
                generally averaged around 58 F.

           10.  Movies and Slides - Movies and slides of the Air-Jet Boom Performance Tests may be
                obtained on request from:  John S. Farlow, Project Officer
                                           Oil and Hazardous Materials Spill Branch
                                           U. S. Environmental Protection Agency
                                           Edison, New Jersey 08817

-------
          Tests started using the modified 3/4- inch-20 degree
nozzle configuration.  The boom was deployed at 45 degrees and
heavy oil was used.  Poor diversion during Test 5-2 was probably
due to uneven oil distribution or poor alignment of the oil
slick with the leading edge of the boom.

     Tests 10-2 through 15A-2:

          The inflatable  sections were  changed to the l£-inch-
20 degree nozzle configuration.  Compared with the previous runs,
performance was improved.  For example, compare Test 7-2 with
Test 13-2, where diversion improved from 75 percent to 90 per-
cent, respectively.

     Tests 16-2 through 20-2;

          The deployment  angle was changed from 45 to 30 degrees.
At 2 knots (Test l8-2), the boom diverted a 1-millimeter slick
with 100 percent efficiency.  With the  same slick thickness at
3 knots in a 4-foot harbor chop  (Test 19A-2), the boom diverted
about 80 percent.

     Tests 46-2 and  47-2:

          These tests  indicate that slicks up to 6 millimeter
can be diverted effectively (95 percent) at 1 knot, and a 3-milli-
meter slick can be diverted with the same performance at 2 knots.

     Tests 31-2 through 36-2:

          Increased  wind  speed and a change in direction caused
the oil slick to shift alignment with the leading edge of the
boom.  During Test 34A-2, the fairing on the inflatable section
"dug" into a wave, causing the section  to fold.  These tests were
repeated later.

     Tests 37-2 through 40A-2:

          These tests  were conducted at 30 degrees with light
oil.  Tests 53-2 and 54-2 indicated that 80 percent of the oil
could be diverted at 3 knots, whereas 60 percent was diverted at
4 knots.  Test 51-2  showed that a 5-millimeter slick could be
diverted at 1 knot with no loss.  A 3-millimeter slick could be
diverted at 2 knots with  about 10 percent loss.

     Tests 32R-2 and 32A-2:

          Test 32R-2 was  repeated because of poor alignment  of
the leading edge of  the boom with the oil slick.  With proper
slick alignment, diversion improved to  80 percent.  Test  32A-2
was conducted to further  investigate the importance of slick
alignment.  Using the  conditions of Test 32R-2, Test 32A-2 was

                               71

-------
conducted with a 12-foot wide oil slick so that it was aligned
with the trailing edge of the boom and with the opposite edge of
the slick 3 feet within the leading edge of the boom.  Comparing
Test 32R-2 with 32A-2, diversion increased to 100 percent. There-
fore, it is probable that oil losses are greatest near-the lead-
ing edge of the boom.

     Tests 55-2 through 57A-2:

          These tests also indicate-how important slick align-
ment is.  Compare., for example., Test 56-2 with Test 5&A-2 or
Test 57-a with Test 57A-2.•

     Tests 38-2 through 59B-2:

          The following test demonstrated the effect of reduced
air supply pressure.  Pressures as low as 1 PSI were supplied to
the get pump (Test 58B-2).  The correlation between inlet pres-
sure to the jet pump and compressor capacity is given in Figure
7 •

     Test 60-2:

          Various types of debris including wood pallets, timber
with nails, milk boxes and 5-gallon cans were tossed off the
tow bridge in the path of the boom.  In the case of debris with
high freeboard (e.g., milk box), the boom "blew" the debris away
from the boom, whereas debris with low freeboard (e.g., timber)
passed underneath the boom without snagging.

     Test 6l-2;

          Test 6l-2 was similar to Test 54-2, except the slick
thickness was reduced.  Diversion increased from 80 percent to
85 percent.

NOTE:  Performance tests were continued on November 2, 1977.
                                                     (Table 5)
     Tests 1-3 through Test 9-3:

          The boom deployment angle was changed to 20 degrees.
at 4 knots, the boom diverted a 3-millimeter slick 'with 70 per-
cent efficiency.  When the tow speed was reduced to 3 knots, the
efficiency increased to 90 percent (Test 3-3)."  With the addi- ''
tion of the medium regular waves, the performance was unaffected
at both 3 and 4 knots.                    '  -.

     Tests 10-2 through 17-3:

          With light oil, performance was -generally the" same as
with heavy oil.  During Test 13-3, the float submerged at 4'knots.


                               72

-------
     Test 18-3:

          This test is of special interest because it was con-
ducted during high winds and heavy rain.  Compared to Test 6~3,
which was conducted in calm weather, diversion performance was
reduced by 10 percent to 80 percent efficiency.

     Test 19-3 through 35-3: ' -   :              '

          These tests were conducted at reduced operating pres-
sures.  Using-'pressure as low- as" 5~ PSI, 100 percent'" efficiency ;
was obtained at 1 knot (Test 21-3).  Increasing the current to 2
knots., the efficiency dropped to,oO percent (Test-29-3).  The
addition of medium regular waves, however} reduced performance
markedly to 50 percent, pointing,out the importance of air pres-
sure from;-the  standpoint of structural support (Test 34-3).

Summary of Results

     Test results are,summarized in Table 6.  The performance of
the modified boom was'improved,  compared to the results of the
Proof Tests (Table 2).  It should be noted, however, that compari-
sons between the Performance Tests and the Proof Tests, based
only on estimated diversion, are not totally reliable since there
were several differences in the  test conditions; for example, the
weather conditions.  Cold weather during the Performance Tests
caused the oil distribution over the free surface to be uneven
(heating the oil in the bridge storage tanks prior to distribu-
tion tended to partially reduce  this problem).  Differences in
the-wave conditions and in- th-e test oils are noted^ in Tables 1,
4 and 5. ';                    .

     Somej general observations are:

     1.  The l-^-inch-20 degree nozzle was better than the 3/4-
inch-45 degree nozzle..  For example, at 3 knots, the boom, when
deployed at 30 degrees- to :the.- flow,-diverted 85" percent, whereas
during the.Proof Test, only 60 percent.was diverted.

     2.  Increased performance 'is also obtained when the boom  is
deployed at 20 degrees to the flow.

     3.  Wave  conformance (and therefore diversion  efficiency)  im-
proved with the l-^-inch-20 degree nozzle because of lower internal
air pressure.     ,                              <

     4.  Oil losses at the higher speed range  (>2 knots) occurred
predominately  along the first 2  or 3 feet of the boom from the
leading edge.  Loss also occurred near the center section, al-
though to a much lesser extent..
                                73

-------
        TABLE  6.   SUMMARY  OF  ESTIMATED  DIVERSION DURING
                  OHMSETT PERFORMANCE  TESTS
Boom Angle
20 Degrees
(~3-mm slick)

30 Degrees
(~2-mm slick)

45 Degrees
(~1.5-mm slick)

Speed
(Knots)
2.0
3.0
4.0
2.0
2.5
3.0
1.0
1.5
2.0
Diversion (Estimated)
Calm
Water
100$
90$
70$
100$
90$
85$
100$
100$
75$
Regular
Waves (MR)
90$
70$
95$
-
80$
-
Harbor
Chop (HHC)
90$
80$
-
90$
80$
100$
80$
-
      5.  The fairing, mounted on the leading edge of the boom,,
prevented folding up to 6 knots with the 3/^-inch-20 degree noz-
zle.  Using the l-^-inch-20 degree nozzle, the maximum tow speed
was just under 5 knots.

      6.  The modifications to the support float enable it to be
towed at slightly higher speeds.  When deployed at 20 degrees to
the flow, however, the /support float was unstable at 4 knots and
did flood on one occasion.

      7.  Changing to the clamping arrangement prevented the in-
flatable section from "blowing off".
                               74

-------
      8.  No damage occurred during the debris test even though
it was much more severe than during the Proof Tests.

      9.  Tests with reduced compressor input demonstrated
that 100 percent diversion can be obtained at 1^- knots (30-
degree deployment),, using only 80 percent of the total avail-
able compressor capacity.
                              75

-------
                          SECTION 10

                    DISCUSSION OF RESULTS

PERFORMANCE RESULTS

Calm Water

     Results of the OHMSETT calm water tests clearly indicate
the strong dependence of diversion performance on the tow speed
V, deployment angle 6 and slick thickness tQ.   The effect of the
oil slick's viscosity is comparatively insignificent.  Diversion
estimates presented in Figures 30.,  31 and 32 (for both heavy and
light oil) show the tendency for performance to decline steadily
with increased speed, steeper deployment angle and thicker oil
slicks.  Figure 33 further summarizes the calm water performance
of the air-jet boom by plotting only the results for 100 percent
and 90 percent diversion* against the normal velocity component
(V sin 6) and the slick thickness.

     Figure 33 is of special interest because it delineates the
general limits of performance.  Specifically,  conditions falling
to the left of the curve indicates  complete diversion with "no
loss"; whereas conditions to the right represent increasing
losses (greater than 10 percent).  The curve also suggests that
the maximum speed obtainable without loss (i.e., for very thin
slicks, t ~0) is about 1.5 knots/sin 6 (or 4.4 knots at a 20-
degree deployment angle).

Waves

     The performance of the boom in waves is nearly the same as
it is in calm water (see Table 6).   Loss rates in waves generally
exceed calm water losses by about 5 "to 10 percent.  To a large
extent, this insensitivity to waves is attributable to the boom's
structural and seakeeping characteristics.  The orientation of
the air jet is properly maintained,  despite the changing height
and slope of the free surface.  The air-jet's interaction with
the oil slick is slightly different in waves than in calm water
because of the boom's response to the orbital velocities that
give rise to surge motions.  In effect, the surface current be-
comes unsteady, causing the oil slick to be diverted in progres-
sive "sweeps".  This "sweeping action" may contribute to greater
 Note:  These results have the highest accuracy.

-------
  100
  90
2 80
uo
Qi
UJ
   70
   60
: A A









1-3-


CALM WATER
9-= 20°
A~3mm SLICK
A~5.5 mm SLICK






/LA
2-3
^
5-3

i


A
m
14-3
X
/ 	 1—
A
/^A


* V



S
A
/ \
': 4-3

                                   3         4

                                  .   FT/SEC
0.5     1.0
                               .5      2.0

                                     KNOTS

                                  VELOCITY, V
2.5     3.0     3.5
4.0
          Figure 30.     OHMSETT Performance  Test results (  6 = 20° )
                                    77

-------
  100
   90
g  80
Q  70
LU
t—


I

I—
LO
LU

   60






i 	 w —
51-2


	 w__,
16-2


CALM WATER
6= 30°
O ~2mm SLICK
Q ~3 mm SLICK
• ~5 mm SLICK






v^
17-2
— Q 	
52-2



c\
\J
18-2

A


O

— V /
~* V




r~\
{J
53-2
                                   34
                                     FT/SEC
              1
5         6


J        I
             0.5     1.0      1.5      2.0      2.5     3.0      3.5      4.0
                                      KNOTS

                                  VELOCITY, V
         Figure  31.      OHMSETT Performance Test results   ( 6 - 30° )
                                    78

-------
ESTIMATED DIVERSION (£)
O XI CO >O C
0 0 O 0 C






1_T


LJ


CALM WATER
[| „ .8 mm SLICK


_ ~ 1.5 mm SLICK









D





/±
/ T




V






) 1 2 3 4 5 6 ;
FT/SEC
1 1 1 1 1 1 1 I
0
0.5     1.0      1.5      2,0      2.5
                        KNOTS
                     VELOCITY, V
                                            3.0
                                     3.5
4.0
Figure  32.
OHMSETT Performance Test results  (  ti = 45  ),
                           79

-------
 E
 E
LLJ
z
V
V
u
                                       DIVE-RSI ON <90%
                                                 2-5  VSIN9, (FT/SEC)
                                                       9,= 20 , (KNOTS)
                     .0     1.5    2.0     2.5     3.0  9=^0°, (KNOTS)
                                                2'°      6 = 45°, (KNOTS)
                                VELOCITY, V
         Figure 33.   Summary of  OHMSETT Performance Test  results
                     calm water .             '  ••
                                   80

-------
losses in waves.  Another cause of increased loss is bridging of
the inflatable  sections over, adjacent wave crests (see Figure 6b).
In this case, the air jet, raised from the free surface, allows
the oil slick to migrate nearer to the boom.  Upon returning to
the free surface, the air jet drives the oil slick (now closer to
the boom) into  the water column, generating oil droplets that
pass beneath the boom.  The  light oil had a greater tendency to
break up with agitation under these circumstances.

     Oil loss in waves was also aggravated by structural prob-
lems.  A particular problem  at high speed and shallow deployment
angles was for  the fairing on the leading inflatable section to
"dig" into approaching wave  crests.  The impact caused intermit-
tent buckling,  which disrupts the continuity of the air jet.
This type of failure may be  lessened by using a lighter weight
fairing on the  leading edge.  A proposed design has an inflatable,
all-fabric, hemispherically-shaped end piece that would eliminate
the weight of the plywood end plate and Fiberglas fairing.

Reduced Power

     Under certain circumstances, the air (power) supplied to
the boom can be reduced without loss of performance in calm water*.
For example, test results (Figure 3^) show that the boom can di-
vert 100 percent and 1 knot  (8 = 20 degree), using only 5 percent
of the rated compressor power (Test 21-3).  Similarly, at 2 knots
(9 = 20 degree) 100 percent  can be diverted using only about 30
percent power (Test 27-3).   At higher speeds, however, a power
reduction will  cause increased losses.  For example, at 3 knots
the performance drops from 90 percent (Test 3-3, 100 percent power)
to 80 percent when operating at the 30 percent power level  (Test
23-3).

     Conditions of V, 0 and  t, under which power can be reduced
from full power without a loss in performance, are those which
fall to the left of the "no  loss" curve given in Figure 33.  The
results of Test 21-3 demonstrates this correlation.

     Savings in compressor power are made at the expense  of  the
boom's structural characteristics, however, because of  the  link
between the boom's strength  and internal air pressure.  Consequently,
the inflatable  section folds at lower speeds and forces restoring
the section's shape are weaker.  Test 25-3  (Table 5) illustrates
this point.  The leading inflatable section normally folds  at 5
knots (full power), but folds at 3 knots when operating at  the 10
percent level.  Moreover, in waves, the reduced  stiffness accentu-
ates the loss in performance.  For example, compare Tests 29-3 and
^Clearly there are numerous operational advantages for this:
 smaller compressors are required, fuel costs are reduced, and
 logistics are simplified.


                               81

-------
34-3, shown in Figure 3^.  -Here the influence of medium regular
waves causes the diversion at the 10 percent power level to drop
from 80 percent (in calm water) to 50 percent.  In contrast.,  the
effect of these waves at rated power is negligible (see Table 6),
                              82

-------
z

o

IS)
C£
LU

^

Q

Q
LLJ
I—
<


P
I/I
      MINIMUM POWER

        (INFLATION)
     100
                               r\
                                                   RATED POWER


                                                            100
                                              COMPRESSOR

                                                 POWER
                                          9 =20, i_ = 3 mm
                                               Q 1  KNOT, CALM

                                               Q 2  KNOT, CALM

                                                  2  KNOT, HHC

                                               A 2  KNOT, MR
                                                  3 KNOT, CALM
60
      50
                       JET PUMP INLET PRESSURE ( psi )
         Figure 34.     Effect of reduced compressor  capacity on
                        diversion performance.

O
oo
CO
LLJ
O


-------
                          REFERENCES

1.  Wicks, Mo  Fluid Dynamics of Floating Oil Containment by
    Mechanical Barriers  in  the Presence  of Water Currents.
    Presented at API-FWPCA  Joint Conference on Prevention and
    Control  of Oil  Spills,,  New York., December 1969.

 2.  Miller,  E., Lindenmuth, ¥. and Abrahams, R.  Experimental
    Procedures Used in the  Development of Oil Retention Boom
    Designs.  Presented  at  The Society of Naval Architects and
    Marine Engineers, Marine Technology, July 1972.

 3.  McCracken.  Performance Testing of Selected Inland Oil Spill
    Control  Equipment.   EPA-6002-77-150, August 1977  (Prepared
    by Mason & Hanger-Silas Mason Co., Inc. for the U. S. Environ-
    mental Protection Agency).

 4.  Ayers, R. R.  A Rigid,  Perforated Plate Oil Boom  for High
    Currents.  EPA-600/2-76-263, December 1976  (Prepared by Shell
    Development Company  for the U. S. Environmental Protection
    Agency) .

 5.  Fliigel,  G.  The Design  of Jet Pumps.  National Advisory Com-
    mittee for Aeronautics, Technical Memorandum No.  982, Wash-
    ington,  July
 6.   Mueller,  F.  N.   Fast Current  Oil  Response  System.  DOT CG-D-
     115-75, April 1975  (Prepared  by TETRADYNE  CORPORATION  for
     the U.  S.  Coast Guard Office  of R&D )  NTIS  AD-A-020-171.

 7.   Brunner,  D.  E.   Materials  for Oil Spill  Containment  Boom.
     Technical Note N-1440,  Civil  Engineering Laboratory, Port
     Hueneme,  California, NTIS-AD-A026 139, June  1976.

 8.   Timoshenko,  S.  and  Young,  D.  H.   Elements  of Strength  of
     Materials, Fifth Edition,  D.  Van  Nostrand  Company, Inc.,
     New Jersey,  1968.

 9.   Baumeister,  T.  and  Marks,  L.   Standard Handbook for  Mechani-
     cal Engineers,  Seventh Edition, McGraw-Hill, New York, 1967.

10.   Hoerner,  S.   Fluid  Dynamic Drag,  published by author,  1958.

-------
                     APPENDIX A
            TABLE A-l.  DESIGN DRAWINGS
HYDRONAUTICSj
Incorporated
 Drawing No.
           Component
Page
 No.
  7705-001

  7705-002

  7705-003


  7705-004



  7705-005
Overall Assembly

Inflatable Section

Inflatable Section End Plate with

Rigging

Jet Pump Center Section with

Rigging Turning Vanes

Jet Pump Nozzle
  92
                          85

-------
DWG. NO.
T705-OOI
                                                                PLKM  VlfcW
                                                           \MR J&T OIL &OOM
                                                 86

-------
          A-2
                 TOLERANCES. UNLESS OTHERWISE SftOFKD-
                              E.^>lCWfcO TO
                              - SUt UT COKlD
                  170^-004  JfcT PUWP
                                        I DWG. NO.
                  MR Jt-T CHL BOOM
                   HYDRONAUTICS, INCORPORATED
                       AIR JfcT OIL &OOM
                    vy.r-o"
                        I
                                         DWG. NO.
                                         77O5-OOI
87

-------
DWG. NO.
77O5-OO?.
                                                          88

-------
                             DOUBLE.E. FV_A.F=, FOi_O
                            TO  KJE.CSE SIDE,  FOE. F
                                RMS. SIDE FOE. F=C_ V
           STETCHtwG PA,TTE_TSwj
           POC. DOO&UE.E.
        ri_A.T  PWEEl-J
6E, ee_Q'D
&S BE-Q'D
                                                         TOLERANCES, UNLESS OTHERWISE SP£Ofl£&
                                                                                           MtMAU-t HACTJ t

                                                                                                4 HACtl t
                                                            •4-E> MIL- x. A. X A-  /V
                                                            A-& MH_ x 4- X A-
4.5 _Mi\.
    F"W

1-S MIL K
                                                                FO.BE.lC
                                                            A-& w\\u K a^fto ^  no
                                                                                         L-lO'iO  K.E..
                                                                                          Ccooi_&.v
                                                                                           1DWG. NO.
                                                                                           I TtOS-OOl \
                                                             HYDRONAUTICS, INCORPORATED
                                                               MR JtT  OIU

                                                                         MR DUCT
                                                                                  o»     wen
                                89

-------
DWG. NO.
77O5-QO3
                                                                                    TH(3L) PC,
                                                                                      \0 PLCS
                                                                        \
                                                  90

-------
           B-B
DOOBUE STITC.H1VJC*
   TH\& CORKJfcR
(TVP TOP tf &CTTTOM
  OF
                 KXHtAHCES, UNLESS OTHOWOC SHOFB).
          ADDED MOO
           <. Dtr*,n_S>
                                        .iKl. giQ  x. "14- \
                                            1 DWG. NO.
                   SHEfcT
                   A-^a M\\_
                     PLYwCOO
                           MtE. DUCT
                   PL&X.I&L& ME DUCT
                                           COOL&.V Co
HYDRONAUTICS, INCORPORATED
                       MR  JET OIL  BOOKA
                             ME OUCT
                                             DWG. NO.
                                             17O5-OO2

-------
92

-------
                         TOLERANCES, UNLESS OTHERWISE SPECIFIED*
                         FtAcnom AM> WHOU MI mm ± Vt^
                         HMKACI MUM   tJLt+S
                         UMOV1 All. MMU. IUAE Ml IHMT EMU. MMMU*
                                  PAT1
                               iX SOFT SOLDER ASSEMBLY
                                n FLflRt vt, MIU  FL.AN&E on EACH (
                                 DUCT 4 SOLDER" FLANGE iw ptflCE
                                i MATCH MARK flS3Efl&Lie3-
                             \t. *. <, \_d  Co
                            LOCK Wfl5H£R
                            POP  RIV£T - '/B DlA. , ALUM.
                             AO (45) ABS	
                            POP RIVET " !/8 DiA- . A
                            TRAMSITlOW * LOCK S
                            DLJCT * LOCK s
                            QUSSfef
                             Ife-  I ^
                                                        IB-9 CORR STtEL
                                                        ie-8 CORK. STSEL
                                                             FASTEN6R CO
                                                        604I-T4 ALL/M
                             VK, * z  • ?z
                                                         I DWG. NO.
                                                         17705 - C
                                                                 004
                                                        6O6/-T4 ALUWt
                                                        JOfJ£S f HUNT
                            HYDRONAUTICS,  INCORPORATED
                                   AIR  JLF  OIL  BOOM
                                         . it !   PL-MP
                                   DlTlAO AbStMBLY
                                          77O5.0741
DWG. NO.
7705-004
93

-------
DWG. NO.
77O5-005
                                                 BEE
                             94

-------
                                   AMD
                                   TO 5tLLWOUTH
       i "77O5J-OO4-
FOR B&LLMOUTH
         &tLLMOUTH KT
        PETKlL. 1
            TO fefcLLMOOTH /
                                    O
                                                 IOLERANCES, UNLEffi OTHERWISE SPECIFIED-
                                                  TO&Er
                                                                           I DWG, NO.
                                                                           "
                                                    £a' O.P K.1'1 P ^ 1C.' Ud
                                                    .' QD ^.^-fe \P. x \
                                                  TUfolkJCq
                                                    ' o p.^a.' i.o, •
                                                                       1 COPPfcR,
                                                                         TVPf L" COPPfcK
                                                   HYDRONAUTICS, INCORPORATED
                                                        AIR J&T OIL&OOM
                                                           KJOZZLfc SPIDfcR
                                                                     ^ COH&KJ
                                                                           7705-005
                            95

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                         APPENDIX B

                   EPA DESIGN GUIDELINES


     Guidelines for the design of the Air-Jet Boom were outlined
in Request for Proposal CI-76-0136, solicited by the U.  S.  En-
vironmental Protection Agency during April 1976.  In part,  they
were established, based on the work of Mueller (Reference  6)  who
used air jets for similar purposes.

     Because these guidelines provide a foundation for this work,
they are given below:

     (1)  The boom shall be approximately 33 feet in length,
          2 feet in diameter and have a cross section approxi-
          mately of that in Figure B-l.

     (2)  The material of construction shall be fabric rein-
          forced plastic which is capable of being fastened
          together by simple means, using heat seal or equiva-
          lent technology.

     (3)  For strength purposes, the boom shall be designed
          to survive in a 10-knot river and operate effectively
          in a 6-knot current with debris.

     (4)  The flexible, metal, ballast/tension member shall be
          either chain or cable, suitably coated to permit use
          in fresh, brackish or seawater, and enclosed in a
          fabric sleeve.  It shall be located so as to help
          counteract the reaction of the jet.  Figure B-l shows
          the approximate location.

     (5)  The air required for inflation and for the air jet
          shall be supplied by commercial grade, gasoline or
          diesel powered air compressors of the sort commonly
          available for tent.

     (6)  The high-pressure, low-volume-air output from these
          compressors shall be led by means of flexible hoses
          to one or more venturi nozzles attached directly to
          the boom section.  The nozzles shall supply low-pres-
          sure, high-volume air to each boom section.  At least
          15.,000 cubic feet per minute at 3.25 inches water
          pressure will be required.

                              97

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                                        ENLARGEMENT OF (7)
9) SECTION AA
                                             m
 ?)

®


®
                                                                              Fabric Reinforced Vinyl

                                                                              Fabric Pouch for Ballast/
                                                                                Tension Member
                                                                              Fabric with Holes

                                                                              Weld

                                                                              Spiral Corrosion-Resistant
                                                                                Spring

                                                                              Bal last/Tension Member
                                                                                (for Dynamic Balance)
                                                                              Rigid Plastic Nozzle
                                                                                Assembly

                                                                              Air Flow ^80 FSP @ Water
                                                                                Surface Slant Distance
                                                                                About 7" - 14"

                                                                              3/4" Wide Nozzle  of Var-
                                                                                able Length & Spacing
                                                                       Note:  Air Flow Through
                                                                              Open Zones
                      Figure B-l.   Proposed EPA Air Jet Boom cross section.

-------
 (7)   The rectangular air-jet  nozzles  shall  be  3/4-inch
      wide and of variable  length and  spacing,  as needed
      to produce the required  velocity distribution  a)
      within the boom, b)  from the nozzles.,  and c) at
      the water surface (at least 80 feet  per second is
      required at the latter location)„  The axis of the
      nozzle shall make an  angle of 45 degrees  with  the
      water surface, and the slant distance  shall be 7 to
      l4 inches (Figure B-l) under typical wave conditions.

 (8)   Prior to starting the compressor,  or in the event
      that it should fail,  the boom shall  float when de-
      ployed and shall easily  support  the  associated hoses,
      nozzles, attached mooring apparatus  and any other
      appurtenances.  For  example, a light,  internal spiral
      spring could be used  to  prevent  collapse  in the event
      of loss of air pressure.

 (9)   The design shall be  easily deployed, deoiled,  stored
      and capable of interconnection with  conventional booms,

(10)   The boom configuration shall be  clean  and simple.

(11)   The boom and its supporting equipment  shall be highway
      transportable by a 3/4-ton pickup  truck.

(12)   The boom and its supporting equipment  shall be de-
      signed to have the capability of operating continu-
      ously without a breakdown for l4 days.
                          99

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                          APPENDIX  C

                       FABRIC SELECTION

     The suitability of various fabric materials for use  in the
construction of oil booms was considered by Brunner (Reference 7).
It was found that fabrics acceptable for this service are.,  in
general, composed of a woven substrate and a natural or synthetic
elastomer coating.  The woven substrate  usually accounts  for mech-
anical properties (e.g., strength of the fabric), while the coat-
ing characterizes the physical and chemical properties.  For the
present application, the following properties were considered an
important criteria in substrate and coating selections:

          Break strength                (Substrate)
          Tear strength                 (Substrate)
          Creep resistance              (Substrate)
          Flexibility                   (Coating)
          Puncture resistance           (Coating)

          Abrasion resistance           (Coating)

          Chemical and Petroleum
               Resistance               (Coating)
          Repairability                 (Coating)

          Heat sealing ability          (Coating)

     Samples conforming to these criteria and capable of with-
standing estimated loads (Appendix D) with an adequate factor of
safety were acquired from six major manufacturers.  After screen-
ing the samples and considering recommendations in Reference 7,
a polyester substrate with a urethane coating was selected.  The
physical properties are as follows:

          Tensile strength      135 pound/inch  (warp)*
                                160 pound/inch  (fill)t

          Tear strength         440 pound/inch  (warp)
                                330 pound/inch  (fill)
^Refers to the direction along the length of the fabric.
tRefers to the direction across the width of the fabric (selvage
 to selvage, typically 60 inches).

                               101

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          Thickness,  total

          Weight, total
          Weight^ substrate

          Fiber
.030 inches

30 ounces/yard2
5.5 ounces/yard 2
2,000 deniert (fill;
1,000 denier (warp)
     Tests of the heat-sealed joint efficiency were conducted
 for  1-inch lap joints.  Results, based on three specimens, were
 that the  joints were 100 percent efficient and failure occurred
 in the  substrate without rupturing the coating.  Long-term creep
 tests of  the fabric are given in Figure C-l.
^Refers to the weight in grams of a 9,000 meter length (i.e., a
 measure of cross-sectional area).

                              102

-------
o
CO
        n

         o
Z
g

oo
Z
               10
T
 12"

1
                                                                             O
                                                              1=2 POUNDS/INCH

                                                                 SPECIMEN WIDTH

                                                                 5.25 INCHES
                                                  2         5


                                                TIME, HOURS
                                                         10     20
              50
                           Figure C-l.  Dead  load creep tests.  (Summary of results  ).

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                         APPENDIX D

                    STRUCTURAL ANALYSIS  OF
                   THE -INFLATABLE SECTIONS

STRUCTURAL STABILITY.

      Assuming the inflatable section is thin  (weightless) and
 supported by internal  air  pressure with no  external loads, the
-membrane stresses are  uniformly distributed in  the axial circum-
 ferential directions and calculated  from the  equations:
 and
                           a
                            o
                                                              [1.1
                                                              [2]
 where
         a   = axial stress  due  to  air  pressure, pounds/inch2
          a
           ° •'      •                    ;•  •             :
         a    =  circumferential  stress  due  to air pressure,

           °  .pounds/inch2          .; .
           p-=-internal-air'pressure,  inches of water

           r =  radius  of the inflatable  sections,  12 inches

           c =  conversiony  .036 psi/inch of water
           f =  fabric  thickness,  .030  inches  (see  Appendix C)

 The resulting  strain  causes"the inflatable  section to increase
 in length  and  diameter.

      With  external loads acting (e.g.,  weight,  drag,  etc.),  the
 distribution of stress, and strain will  become nonuniform causing
 lateral and/or torsional deflections  of the  inflatable section.
 These stresses can be calculated by using linear  beam theory and
 the principle  of superposition (Reference 8)  where the net  stress
 is due to  the  algebraic sum of the stress1 due to  air  pressure and
 the stress' due;-to external load.  As  long as  the  net  membrane
 stresses are positive (tensile)  at each point on  the  fabric,  the
 theory is  valid.  However,  if  the net stress  should become  nega-
 tive (compressive), the inflatable section  can  become unstable

                               105

-------
or buckle since the fabric cannot support compression.  There-
fore., the criterion used for structural stability is that the
membrane stress must always be greater or equal to zero.

     Several conditions of loading are considered below:

Case One
     Inflatable section floating with uniformly distributed
horizontal load-cantilever support  (see Figure D-l).

     From the linear beam theory, the stress due to uniform
load on a cantilevered beam is calculated by the equation:
where

        a   = axial stress due to horizontal load, pounds/
         ai   inch3

          uu = uniform horizontal load_, pounds/inch

         £1 = length of the inflatable section, 165 inches

          r = radius of the inflatable section, 12 inches

          I = moment of inertia, 244 inches4

        (Note:  a   is zero for small deflections)
                 Cl

     Superimposing the axial stress, due to internal air pres
sure, (Equation 1), the minimum and maximum membrane stresses
(at the locations indicated in Figure D-l) are then:
                      amin
and
but since
                 a     > 0 (stability criteria)  ,          {6]
                  amin
the maximum uniform horizontal load, which can be supported
without JLoss of structural stabi
by combining equations 4 and 6):
                                   ,
without JLoss of structural stability (oj ), is (determined
                                       s
                              *   S?-P                   C71
                             106

-------
o
XI
                                                      - a  + a
                                                 a       a    a
                                                 max.   o   i
                                                                  UNIFORM LATERAL LOAD, u>
                                                                                           max
                    Figure D-l.  Inflatable section under uniformly distributed horizontal

                                load - cantilever support.

-------
or

                        £ (1.1 x 10'2) p    .                 [8]


Further, if the design air pressure, 3.25 inches of water,
is assumed

                      uu  s .036 pound/in.                     [9]
                       5'

or
                         £ .430 pound/ft    .                [10]


     Hence loads in excess of .430 pounds/ft delineate the
threshold of buckling (folding).

     Using the load estimates from Appendix D, page 106, a
maximum value of uu was obtained.'" The following assumptions
(worst case) were used:

            (1)  The boom is deployed at 8 = 90 degrees
            (2)  The tow speed is V = 6 knots (~10 feet/second)

            (3)  Loads are due to drag and nozzle reactions
                 (I = 3/4" and a = 45 degrees)

so that
                      uu    - 1.85 pounds/fpot   .            [11]
     By comparing with Equation 10,

                           uu    » uu    •,                    [12]
                            max     s   3                       J

indicating that the inflatable section will probably buckle.

Case Two
     Inflatable section floating with, ^uniformly distributed
horizontal load - cantilever with simple end support (see
Figure D-2) .  For the cantilever with simple end support, the
membrane stresses are given by the expression,
Superimposing the stress due to internal air pressure (Equation
1), maximum and minimum stresses are then:
                               108

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                                            UNIFORM LATERAL LOAD, ti-
                =(7   -or   > 0
           a  .    a    a
            mm    o    i
                                                                     max
Figure D-2.   Inflatable section under uniformly distributed horizontal

             load - cantilever with simple  end support.

-------
                       mm
and
                             c
                     ""tax " ~Sf'
Using the stability criteria (Equation 6),

                       ^ <: Y.ijli-^j p                     [16]

or
                          z (7.8 x 10-2) p   .              [17]

     If the design pressure, 3.25 inches of water, is
assumed
                       uu  <: .253 pound/inch                 [18]
                        S
or
                          £ 3.^9 pound/foot  .              [19]

     Comparing to the estimate value uu    (given by equa-
tion 11),
                             uu    <  uu                      [201
                              max     s

indicating that the inflatable section is stable.
     The maximum horizontal deflection (y   ) can be cal-
culated by the expression

                                 Err = .72 inches            [21]
where E = modulus of elasticity, 4.0 x 104 psi (see Appendix
D, page 123).
Case Three
     Inflatable section floating with uniformly distributed
moment  - cantilever  support  (see Figure D-3).
     Membrane stresses arising from a uniformly distributed
moment  (m) on the inflatable section cause axial and circum-

                              110

-------
                                 UNIFORM MOMENT, M
                                                      max
Figure D-3.   Inflatable section under uniformly distributed
             moment-cantilever support.

-------
ferential shear stresses, as shown in Figure D-3.  The stresses
here do not contribute to buckling of the inflatable section,
even when superimposed to the previous cases of lateral load*.

     Angular deflection  (cp) of the inflatable section (see Fig-
ure D-3) is given by the expression
                            cp = S-                         [221
                            ^   2GJ

where

         cp = angular deflection, radians/inch

         J = polar moment of inertia, 488 inches*

         G = shear modulus, 7.1 x 10s psi (see Appendix D,
             page 108).

     Based on design guidelines in Appendix B (item 7)5 "the
limit on angular deflection was reckoned-' such that


                   cpc < 1.4 x 10~3 radians/inch  .           [23]


     Combining Equations '[22] and [23] ,


                   m  < +5.77 inch -pounds/inch              [24]

or

                   m  < ±69. 3 'inch-pound/foot    .           [25]
                    O
                                                          /

     Using the load estimates from Appendix D, page 121 y a
value of m    was obtained.  The following assumptions (worst
case were m   used:

     (1)  The boom is deployed, at B '= 90 degrees

     (2)  The tow speed is V = 6 knots, (~lb feet/second)

     (3)  Moments are due to hydrodynamic drag and nozzle
          reactions (I = 3/4",  a = 45 degrees, h = 5 degrees)

such that

                     mmax = 10'8 inch-pounds/foot   .       [26]
*¥rinkling of the fabric, shown in Figure D-3, can occur along
 a helical plane whose angle is related to the initial distri-
 bution of membrane stress.
                              112

-------
     Comparing Equation  [24] with Equation  [26],


                            m
                             max < m
                                    c

indicating  that  the  inflatable  section has  adequate torsional
stability.

WAVE CONFORMANCE

     Based  on a  method s.imilar  to that described in Appendix D3
page 105, calculations are made to indicate the tendency of the
inflatable  sections  to conform  to waves under  static load condi-
tions*.

     Two wave conditions are described below:

Case One
     High waves with wavelengths (X) greater than the projected
length of the  inflatable  section.,  Ij cos  9 - cantilever sup'port
(see Figure D-4-).      :   '

     From the  linear beam theory,  the stress due to uniformly
distributed vertical loads  (§) with  end load (i.e., end plate)
(F) on cantilever., is  calculated by  the equation
                      CT
                       a2
where
         a   = axial  stress due to vertical load, pounds/inch
          a2              ••,

           § = uniform vertical load, pound/inch

           F = end load, 5 pounds.

     Superimposing the axial  stress due to internal air pres-
sure (Equation 1), the maximum and minimum stresses are then
                   a
                    %in ~   2t     I  21   '   I
and
^Unsteady loading is not neglected.


                              113

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WAVE
CREST
WAVE
CREST
                                     V
                                  UN IFORM VERTICAL LOAD
1
' ^
r >
' >
r i
t >
i \
i \
i i
t \
             Figure  D-4.  Conformance  of inflatable section in waves  of
                          long wavelengths  (>^

-------
                      amax           L            J
Based on the criteria like that in Equation [6],
                     a     s 0  (compliance criteria)        [30]

                      amin
for the inflatable sections to contour with the free surface.
     Therefore, combining Equation  [6] and Equation [28]s the

                              rec



                              cl
minimum uniform vertical load requires (§ ) is
                                         s
                              -. -*    .      .                 [31]
                              i •t'l





If the  end load F is  5 pounds,




                  ?   = 1.0 x 10~2 p  - 6.1 x 10~2            [32]
and if the design air pressure is assumed to be 3.25 inches

of water



                   ?  =  -2.85 x 10~2 pound/inch*              [33]
                   S



or


                          > -.34 pounds/foot   .              [34]




     Using the load estimates from Appendix D3 page 1215 a

value of  §    was obtained.  The following assumptions were
   -,        max
made:


     (1)  Lift forces are neglected


     (2)  Weight of the boom is 1.32 pound/foot


     (3)  An upward component of force is due  to the nozzle

          reqction (
-------
since

                           §    > §                          [36]
                            max    s                         L-J  J

the inflatable sections will probably follow the free surface.

Case Two
     High waves with wavelengths (X) less than or equal to
the projected length of the inflatable section, ^t cos 9 (see
Figure D-5) •

     Stress due to uniformly distributed vertical load is
calculated by the equation
                                4-    ir                    [3 ,
                           a! ~ -  12b  I                     L:JM

superimposing the stresses due to internal air pressure
(Equation 1)5 the maximum and minimum stresses are then:
                       min
                     "a    =  ^ -T    '         -  [39]
                      amax     2f     12°  z

Combining Equations [30] and [38], the minimum uniform verti-
cal load required for compliance is
or
                     ?a ^ 7.6 x 10~2 pounds/inch
or
                     §o s: 9.2 x ICr1 pound/foot   .  l   ;    [42]
                      o
Hence j by comparing Equation [42] to Equation [35]


                            ?    < ?                        [43]
                             max    s                       L -3-1

it can be seen that compliance will probably not occur, at
least under static condition.


                              116

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WAVE
CREST
WAVE
CREST
                                      V
                                    UN IFORM VERTICAL LOAD
^
1 \
' \
1 1
1 \
' 1
' 1
' >

                                            BRIDGING
              Figure D-5.  Conformance of  inflatable section in waves
                          of short wavelengths (is

-------
NATURAL FREQUENCIES
     Natural frequencies lateral modes - undamped, fL (see
Figure D-6a)
                 fL = Bn V^  (R6ferenCe 9)             C44]
where
            B  = i(2n-l)
             n   2V     '
             n = modes, 1, 2 and 3
             g = gravity, 386 inch/second2
             A = cross-sectional area, 2.3 inch2
             m = weight, .11 pound/inch
            LI = length of inflatable section, 165 inches
             E = modulus of elasticity, 4 x 104 (see Appendix
                 D, page 108)

                                            £L
             fundamental, n = 1           55 cps
             second harmonic, n = 2      164 cps
             third harmonic, n = 3       273 cps
     Natural frequency - torsional modes - undamped, frp (see
Figure D-bb)

                 fT = Bn   -1T2-    (Reference 9)            [451
where G = shear modulus, 7-1 x 102 psi (see Appendix D,
page 108).
             fundamental, n = 1            8 cps
             second harmonic, n = 2       21 cps
             third harmonic, n = 3        38 cps

ESTIMATED LOADS
     The approximate location of centers of pressure and force
are shown in Figure D-7.
                              118

-------
        0
Figure D-6a.   Natural  frequency  -  lateral modes  (undamped)
                                                     n = 1
                                                     n =3
                              L










Figure D-6b.   Natural frequency - Torsional mode  (undamped)






                           119

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NO
O
                                                                  FORCES / UNIT LENGTH
                                                           W
                                                           D
                                                             H
                                                           D
                                                            "H
                                                           N
                                                           M
x/y
WEIGHT
DRAG, HYDRO-DYNAMIC
DRAG, AERODYNAMIC
LIFT, HYDRODYNAMIC
LIFT, AERODYNAMIC
NOZZLE REACTION  FORCES
NOZZLE REACTION  MOMENT
                        BOUYANCY
                      Figure D-7.  Estimated loads on inflatable section (per unit length ).

-------
Weight^ W

                    ¥ = 2npfr (pounds/foot)                   [46]
where
            r = boom radius ,  1  foot
           pf = fabric  density,  .21 pound/foot3
           W = 2n  (.21)(1) = 1.32 pound/foot
Drag 3 Hydrodynamic., •!>„
                           p  SV 2
                         TT W W
                         —  - (pounds/foot                [4?]
where
            C    =  drag  coefficient,  4.6 x  10~3  (Reference 10)
            UE
            p   =  water density,  62.4 pound/foot2
             w
            V   =  tow speed,  normal  foot/second
             S  =  wetted area

Assuming  still  water conditions
                     S =
                         nR
                         90
where
                             COB
                                -
[48]
             d = boom  draft,  .08  foot  (estimated)
             r = boom  radius,  1 foot.

Combining Equations  [2] and  [3]

                  DH = 3,42  x. 10~3 V2  pounds/foot.

Drag, Aerodynamic, p.

                       VAAOTA"
                 D,  =    ;v	  (pound/foot)                [49]
                  .H.      ^&

where

                               121

-------
          C,..  = drag coefficient, 4.0 x 10"1 (Reference 10)
           p  = air density, .075 pounds/foot3
           A  = projected area, 2 foot2/foot
           Vft = relative air speed, normal, foot/second

                  DA = 9.3 x 10-4 VA2 (pound/foot)         [50]
where
           .2 = lift to drag ratio, (Reference 10).
Lift, L
                           L =  .2 D                        [51]

Nozzle Forces, N , N

           N  = 1.4 x 10-2 -OL	 cos a (pound/foot)        [52]
            x                sc

           N  = 1.4 x 10~s —	 sin a (pound/foot)        [53]
            y                sc
where
           p  = density of water, 62.4 pound/foot3
            p = boom pressure,  inches of water
            £ = nozzle throat,  inches
            a = nozzle impingement angle with free surface,
                degrees
Nozzle Moment, M
       M = N3 (/23+22h-h2 ) - Nx (11-h)   nCfQ^UnS        [54]
where
       h = nozzle height, inches.  Note that the boom draft
is assumed to be 1 inch.  A positive value of M indicates
moments of tendency to rotate the air jet away from the free
surface .  A negative value of M indicates moments of tendency
to rotate the air jet toward the free surface.
                             122

-------
DETERMINATION OF MODULUS OF ELASTICITY AND SHEAR MODULUS

Modulus of Elasticity, E

     The modulus of elasticity was determined by evaluating the
load/deflection characteristics of a segment of the inflatable
section (without the nozzle) constructed with the selected fab-
ric.  The results shown in Figure D-8 indicate linear behavior
up to the point of local buckling or wrinkling of the fabric.
In this range, the ratio of load' to deflection (P/^) is about
6.15 pound/inch.  The modulus of elasticity determined from beam
theory (Reference 8) is
                                           psi    .          [551
 Shear Modulus,  G

     The  determination  of  shear modulus  (G) was carried out
 in a similar way.  The  results given in Figure D-9 reveal
 linear  load/deflection  behavior up to the point of wrinkling.
 The ratio M /    is about 7690  inch pounds per radian within
 this range/    Using  the beam theory, the shear modulus is


                    G = M. [£»]= 7,1 x 103 psi   .           [56]
                        cpi    J
                               123

-------
   2.00
    1.75
   1.50
Z   1.25
O  1.00
u
LU
Q
     .75
     .50
     .25
 POINT OF

'BUCKLING
                                         DEFLECTION
                                LOAD
                                               i
                                                BUCKLING    /

                                                            J
                                       LOAD
                                    DEFLECTION
                                                =  6.15
                                         POUNDS


                                          INCH
                     23456789



                               LOAD (POUNDS )
  Figure D-8.   Load/deflection of inflatable  section for determination
               of modulus of  elasicity.
                                 124

-------
 CN
  'o
 X
Z
Q
Di
Z
g
u
        14
        12
        10
           0
                                   MOMENT
                         D ERECTION-
                            MOMENT
                          DEFLECTION
                                                 ONSET
                                                  OF
                                              WRINKLING"
                                           INCH-POUNDS
                                             RAD IAN
                                                        10
                    MOMENT ( INCH - POUNDS x 10~2 )
Figure D-9.
          Load/deflection of inflatable section for determination
          of shear  modulus
                             125

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
   EPA-600/7-79-143
                                                           3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
   Design, Fabrication and  Testing of the Air-Jet  Oil
     Boom
                                                           5. REPORT DATE
                                                             June  1979  issuing date
                                                           6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
   Steven H. Cohen
   William T. Lindenmuth
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
   Hydronautics, Inc.
   Pindell School Road
   Laurel, MD  20810
                                                           10. PROGRAM ELEMENT NO.

                                                                INE 828
                                                           11. CONTRACT/GRANT NO.
                                                                 68-03-2li9T
12. SPONSORING AGENCY NAME AND ADDRESS
   Industrial Environmental  Research Laboratory-Gin.,  OH
   Office of Research  and Development
   U.S. Environmental  Protection Agency
   Cincinnati. Ohio  U5268	
                                                           13. TYPE OF REPORT AND PERIOD COVERED
                                                                  ina_L
                                                           14. SPONSORING AGENCY CODE
                                                                EPA/600/12
 15. SUPPLEMENTARY NOTES
 16. ABSTRACT
        This report  describes the design, fabrication and testing of the Air-Jet
   Boom.  This hovel boom has the capability to  divert oil slicks under wave  and
   current conditions that normally preclude the deployment of conventional booms.
   Tests at the  EPA'S OHMSETT facility have demonstrated that this boom can divert
   oil slicks at 3 knots with 85 percent efficiency when at 30 degrees to the flow.
   Moreover, with the addition of steep, U-foot  waves, the boom's performance is
   virtually unchanged.

        The key  operational feature is a continuous, horizontally .oriented air
   jet ejected from  along the boom at the water's surface.  Overall, each boom
   module is about 33 feet long and 2 feet in  diameter.  Major components include
   two inflatable sections (ducts) to support  the continous air-jet nozzle and a
   center support float/jet pump.  Some unique features of the structural design
   are low draft (l  inch} and excellent compliance to waves.   Furthermore, the
   sections are  both lightweight and highly compactible for storage.
17.
a.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
   Water Pollution
   Oils
   Booms  (equipment)
   Air
   Rivers
                                              b. IDENTIFIERS/OPEN ENDED TERMS
                                               Spilled  Oil Cleanup
                                               Coastal  Waters
                                               Diversionary Boom
                                                                           COSATI Field/Group
68 D
13. DISTRIBUTION STATEMENT

   RELEASE TO PUBLIC
                                              19. SECURITY CLASS (This Report )
                                                UNCLASSIFIED
                                                                         21. NO. OF PAGES
                                              20. SECURITY CLASS (This page)

                                                UNCLASSIFIED
                                                                         22. PRICE
EPA Form 2220-1 (9-73)
                                            126
                                                                       AUSGPO: 1979 — 657-060/5353

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