6OO281141
"O CONTROL OIL SPILLS
bx
Michael K. Breslin
Mason & Kanger-SiJas Mason Co., Inc.
Leonardo, New jersey 07737
Contract No. 68-03-26^2
Project Officer
3ohn S. Farlow
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory
Edison, New Jersey 08817
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, 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 irade names or
commercial products constitute endorsement or recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency was created because of Increasing
public and government concern about the dangers of pollution to the health and
welfare of the American people. Noxious air, foul water, and spoiled land are tragic
testimonies to the deterioration of our natural environment. The compjexity of that
environment and the interplay of its components require a concentrated and integrated
attack on the problem.
Research and development is that necessary first step in problem solution; it
involves defining the problem, measuring its impact, and searching for solutions. The
Municipal Environmental Research Laboratory develops new and improved technology
and systems to prevent, treat, and manage wastewater and solid and hazardous waste
pollutant discharges from municipal and community sources, to preserve and treat
public drinking water supplies, and to minimize the adverse economic, social, health,
and aesthetic effects of pollution. This publication is one of the products of that
research and provides a most vital communications link between the researcher and
the user community.
This report describes a tool developed at the EPA Oil and Hazardous Materials
Simulated Environmental Test Tank (OHMSETT) facility to control oil slick movement.
A high-pressure, coherent water stream was directed vertically into a body of water,
causing a surface current that controlled movement of an oil slick. Several tests were
performed to determine optimum effectiveness. Results of these tests as well as a
theoretical analysis of the currents produced by the water jets are given. This report
will be of interest to all those interested in controlling 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.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
Cincinnati
in
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ABSTRACT
The ability of coherent water streams to induce a surface current in a body of
water and thus control a floating oil slick was examined in a number of test programs
conducted at the U.S. Environmental Protection Agency (EPA) Oil and Hazardous
Materials Simulated Environmental Test Tank (OHMSETT). The objective of the tests
was to determine whether coherent water streams could serve as an alternative to
fabric booms and water sprays in concentrating, diverting, and containing oil slicks.
The water jets were constructed from standard commercial pipe fittings and
supplied with water from off-the-shelf centrifugal water pumps. They were mounted
on the main towing bridge, they were built into small floats which were angled across
the direction of tow and extended from the bows of a simulated oil skimming
catamaran. Currents of up to 6 kt were induced by towing the water jets from the
main bridge down the test tank. Regular waves and harbor chop or confused sea
conditions were developed by the tank's wave generator.
The tests showed that coherent jets could induce a significant surface current
and move an oil slick with little oil entrainment. The non-breaking waves produced by
the OHMSETT wave generator did not greatly affect performance except where the
jet nozzles were cantilevered off the front of the catamaran and the pitch of the
vessel caused significant changes in the height and attitude of the jet outlet. The best
position for a fixed water jet of the sizes and at the pressures tested was determined
to be vertically directed at the surface of the water with the outlet 0.4 to 1.0 m above
the surface. These tests showed that the vertical forced component of a coherent
water stream was as useful, if not more so, as the horizontal forced component. The
performance of a water jet powered by a 30 kw electric motor/centrifugal pump
system exceeded that of an air jet of compressed air (210 kPa) extended 0.6 m below
the surface and supplied by a 50 kw gasoline-driven air compressor.
This report was submitted in fulfillment of Contract No. 68-03-2642 by Mason
& Hanger-Silas Mason Co., Inc., Leonardo, New Jersey, under the sponsorship of the
U.S. Environmental Protection Agency. This report covers the following six test
periods: August 28 to September 1, 1978; October 30 to November 11, 1978; May 21 to
3une 1, 1979; July 2 to July 7, 1979; July 26 to July 27, 1979; and September 10 to
September 14, 1979, when the work was completed.
IV
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CONTENTS
HI
IV
vi
viii
ix
x
xi
1 Introduction 1
2 Explanation and Basic Uses of Water 3ets to Control Oil Slicks ... 3
Introduction 3
Conclusions 12
Recommendations 13
Test Description 13
Test Procedures 16
Discussion of Results 23
3 Water jets Mounted on a Moving Oil Skimmer 47
Introduction 47
Conclusions 47
Recommendations 49
Test Description 50
Discussion of Results 66
4 Water 3ets Mounted on Individual Floats 81
Introduction 81
Conclusions 83
Recommendations 83
Test Description 83
Discussion of Results 89
References 92
Appendices
A. OHMSETT Description 93
' B. OHMSETT Oil Properties 95
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LIST OF FIGURES
Pae
_ ^ T .* ~ . ' L . 2oCe „,..„.. b
3 r\Ft Ln K-i^i v« d ic;T v .- ^ \K ul ea t j i < 161 '- o ~)>6 ^CU^'-HCC Oj, 3 St 8.1} OHcir V W3 16 T
jet 1 7
4 Static-nary water jet—side view 9
5 Stationary water jet—xop view 1C
fc Moving water jet exhibiting characteristic wave train ................. 11
7 Test set up for oil slick convergence tests 14
8 Section view of convergence test set up 15
9 Test set up for a single water jet test (slick parting tests) 17
10 Water jet nozzle mounted on the main bridge 18
11 M.G. 3ohnson holding an OHMSETT oil slick sighter 19
12 Effect of tow speed on oil slick movement (slick convergence tests) 32
13 Effect of tow speed on oil slick movement (slick parting tests) 33
14 Water jet performance in calm water and waves (slick convergence
tests) 35
15 Water jet performance in calm water and waves (slick parting tests) .... 36
16 Effect of number of water jets on oil slick movement (slick conver-
gence tests) 37
17 Effect of water jet pressure on oil slick movement (slick convergence
tests) 38
18 Effect of water jet pressure on oil slick movement (slick parting
tests) 39
19 Effect of water jet pressure and slick thickness on oil slick movement
(slick convergence tests) 40
20 Effect of slick thickness on oil slick movement (slick parting tests) 41
21 Effect of nozzle diameter on oil slick movement (slick parting tests) .... 42
22 Effect of water jet nozzle height on oil slick movement (slick parting
tests) 44
23 OHMSETT water jet nomograph used for Converging a 1 mm slick
at 4 knots 45
24 Comparison of water jet performance to that of a compressed air
source (slick parting tests) 46
25 USCG ZRV skimmer using water jets to sweep oil 48
26 First generation water jet booms on the OHMSETT catamaran
during a tow test 51
27 Second generation water jets mounted on the OHMSETT catamaran 52
28 Details of second generation water jets 53
29 Test set up for oil skimmer/water jet tests 54
30 Test set up for stationary tests—pivoting a water jet boom 55
VI
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31 Underwater sequence of a water jet parting an oil slick 56
32 Performance of a 1.25 err JD water jet at 4 knots In caJm water (slick
convergence tests) , 70
33 An inwardly-directed nozzle on a single water jet boom mounted on
the OHMSETT catamaran 71
34 Performance of a 1.6 cm ID water jet at 4 knots and 6 knots
operating in -calm water (slick convergence tests) 72
35 Performance of a 2.7 cm ID water jet at 4 knots on a 7-meter and
12-meter boom (slick convergence tests) 73
36 Performance of a 2.7 cm ID water jet a: 4 knots and 6 knots
operating on a 12-meter boom (slick convergence tests) 74
37 Performance of a 2.] err- iD wa:er let at 4 knots (slick
convei-£ence tests) 75
38 Performance of a 2.1 cm ID water jet at 6 knots operating
on a 7-meter boom in calm water (slick convergence tests) 76
39 Water jet angled forward and inward during a calm water test 77
40 Water jet ang'ec forward and inward during a wave les: 7£
41 Tanoern water jets during a tow test SC
42 Isometric drawing of a water jet float 82
43 Test set up for water jet float program 84
44 Water jet floats under tow diverting an oil slick 85
45 Water jet float with gasoline pump 87
46 Proposed water jet float/skimmer test set up 90
vit
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• LIST OF TABLES
Nurr-ber Page
:K Converger.ee Tests 20
2 V.cirix for Siick Divergence Tests 21
3 Test Matrix for Water jet Height Effects 22
4 Slick Convergence Test Results 2^
5 Slick Divergence Test Results 29
6 Water jet Height Effects Test results 31
7 Water jet/Oil Skimmer Feasibility Test iv'atrix 62
8 U.S. Coast Guard Skimmer/Water Jet Test Matrix (Stationary
Tests) 64
9 U.S. Coast Guard Skimmer/Water Jet Test Matrix (Tow Tests) 65
10 Water Jet/Skimmer Test Results . 67
11 Water Jet Float Test Matrix 88
VIII
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ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
crru --centimeter
cm --squared centimeter
e.g. --for example
EPA --Environmental Protection Agency
deg --degrees
fwd --forward
HC --harbor chop
ht --height
i.e. --that is
ID --inside diameter
IND --indeterrninant
kg --kilogram
kPa --kilopascals
kw --kilowatts
kts —knots
m --meter
mm --millimeter
no. —number
Poly --polypropylene
OHMSETT --Oil and Hazardous Materials Simulated Environmental Test Tank
press --pressure
sec --seconds
thk —thickness
u/w --underwater
US —United States
ZRV --Zero Relative Velocity
SYMBOLS
10/20 --Descriptor of water jet nozzle orientation. The first number is the
angle, in degrees, which the nozzle was tilted from the vertical in
toward the centerline of the oil skimmer or catamaran^ The second
number is the angle, in degrees which the nozzle was tilted from the
vertical forward in order to shoot the stream of water "upstream" of the
system.
% --percent
IX
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METRIC CONVERSION FACTORS
METRIC TO ENGLISH
To convert from
Celsius
joule
joule
kilogram
meter
meter
meter 2
meter 2
meter 3
meter 3
meter/second
meter/second
meters/second
meters/second
meters/second
newton
watt
ENGLISH TO METRIC
centistoke
degree Fahrenheit
erg
foot
foot2
foot/minute
footS/minute
foot-pound-force
gallon (U.S. liquid)
gallon (U.S. liquid)/minute
horsepower (550 ft Ibf/s)
inch
inch 2
knot (international)
liter
pound force (Ibf avoir)
pound-mass (Ibm avoir)
psi
TO
degree Fahrenheit
erg
foot-pound-force
pound-mass (Ibm avoir)
foot
inch
foot2
inch2
gallon (U.S. liquid)
liter
foot/minute
knot
centistoke
footS/minute
gallon (U.S. liquid)/minute
pound-force (Ibf avoir)
horsepower (550 ft Ibf/s)
meter 2/second
Celsius
joule
meter
meter2
meter/second
meters/second
joule
meterS
meter S/second
watt
meter
meter2
meter/second
rrieterS
newton
kilogram
pascals
Multiply by
tc = (tF-32)/l.S
1.000 E+Q7
7.374 E-Oi
2,205 E+00
3,281 E+00
3.937 E+01
1.076 E+01
1.549 E+03
2.642 E+02
1.000 E+03
1.969 E+02
1.944 E+00
1.000 E+06
2.119 E+03
1.587 E+04
2.248 E-01
1.341 E-03
l.OOOE-06
tc = (tp-32)/1.8
1.000 E-07
3.048 E-01
9.290 £-02
5.080 E-03
4.719 E-04
1.356 E+00
3.785 E-03
6.309 E-05
7.457 E+02
2.540 E-02
6.452 E-04
5.144 E-01
1.000 E-03
4.448 E+00
4.535 E-01
6.894 E+03
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ACKNOWLEDGMENTS
The work of M.G. Johnson of Mason & Hanger-Silas Mason Co., Inc., in the
development of the water jets and during the test programs described in this report
contributed & great deal to the success of the U.S. EPA water jet program.
Dr. R.I. Hires, Dr. 3.P. BresJin and Mr. D.T. Valentine are gratefully acknow-
ledged for their work in developing the first theoretical analyses of water jets.^'6,7
Mr. 3.S. Farlow, EPA Project Officer for OHMSETT, is gratefully acknowledged
for his technical guidance throughout the test program.
XI
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SECTION J
INTRODUCTION
Two factors that cause the cost of oil spill cleanup to soar are labor and
expensive equipment Inadequacy or failure. This report describes a method developed
by the U.S. Environmental Protection Agency (EPA) that could reduce both of those
costs: The use of a downward vertical coherent stream of water delivered from a high
pressure source onto the body of water containing the oil spill. The result is a. surface
current away from the point of impact. The surface current induced can effectively
control the movement of the oil slick. The device has been named the water jet.
The air-entraining properties of the water jet are what make it valuable to oil
slick control. Once the air begins to bubble up to the surface water is brought with it.
When a bubble reaches the surface, the displaced and entrained water dissipates
radially outward from the burst bubble, forming a surface current. The entrainment of
air and the turbulent nature of a water jet hitting a water surface is familiar to
anyone who has washed dishes in a sink and turned up the water pressure to agitate the
water and form soap bubbles.
A water jet can be constructed of common pipe and fittings using any of the
many commercially available pumps to supply the water. Properly assembled and
positioned, it can operate with minimal supervision and provide rugged installation to
oil spill recovery work. Workboats and shipping may pass within a few feet of a float
with a water jet without damaging the oil slick control system. In contrast, a fabric
boom could be torn or sunk if a vessel were to sail into it. In all of the six test
programs conducted by the EPA Oil and Hazardous Materials Simulated Environmental
Test Tank (OHMSETT) (Appendix A), the only problems encountered were improperly
assembled hoses that parted because of the pressure, the water pump losing prime
after being shut down after a test, and an object being lodged in the nozzle of the
water jet (e.g., a small rock that was in the hose that supplied the jet). All problems
were corrected within minutes.
The technique of using streams and sprays of pressurized water to control oil
slicks has been known for sometime. Reports on the use of .fire hose streams to
control oil slicks have been published by the U.S. government. ' From a literature
and patent search and from statements of experienced oil spill cleanup contractors and
oil spill recovery equipment manufacturers, it was found that the horizontal velocity
component of the water streams is used to create a surface current and move oil,
while ihe vertical component is generally overlooked or directly declared to have no
value. The valuable vertical component of the coherent water jet is what this report
is primarily concerned with.
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A feasibility test to examine the usefulness of water jets as a substitute for a
fabric transition piece between converging booms and a skimmer was conducted
simultaneously with these tests and appears under a different cover.
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SECTION 2
EXPLANATION AND BASIC USES OF WATER JETS TO CONTROL OIL SLICKS
INTRODUCTION
The development of the water jet began as a method to Increase the accuracy
of testing oiJ spill control and recovery devices at OHM SETT. Primary to the
operations at the OHM SETT facility is the ability to control oil slicks on the water's
surface after they have been deployed from the oil distribution system so that the oil
slick effectively enters the device being tested. The oil must be laid down on the
water at a sufficient distance from the device to allow the oil to recover from the
shock of being deployed from a moving source (the main bridge) onto the stationary
water surface. Deploying the oil from the "upstream" side of the bridge is sufficient
for the oil to form a fairly uniform layer before it contacts the test apparatus intake.
However, the time between deployment and contact with the test device allows the oil
to spread laterally. This spreading of the oil can cause some of the oil slick to pass
around the test device's intake. Such a loss of oil must be estimated from visual
observations and thus can be very subjective. These inexact observations can result in
test data that show more than 100% throughput efficiency for an oil skimmer.
Several methods have been tried to control the width of an oil slick to conform
to a device's intake dimensions. The use of rigid oil containment plates worked well at
speeds to six knots in calm water and regular waves. However, when a harbor chop
wave condition was encountered, the plates were subjected to side forces large enough
to destroy their structural integrity. The use of a pair of flexible oil containment
booms was somewhat more successful in harbor chop conditions, but even at low
speeds in calm water the turbulence caused by the floatation members and attachment
mechanisms of the booms could adversely affect the performance of the device being
tested. Another method was the use of floating ropes to guide the oil to the test
device. Braided rope and urethane foam-covered rope worked very well in calm water
and waves at speeds to six knots (regular stranded rope tended to skid sideways on the
water's surface in the direction that the strands were wound). However, with both the
booms and the ropes insufficient tension could result in the fabric or rope buckling and
folding and causing turbulence, while too much tension caused the rope or fabric to
bridge the wave troughs and allow oil to escape beneath it.
The use of fire hoses to push oil to or away from objects or to clear areas ahead
of an advancing skimmer has been used for years at OHMSETT and led to the concept
of using water jets for guiding oil. Fire hose streams directed at the water surface,
move oil primarily by two mechanisms. The first is a current formed by the impact of
the high velocity water droplets from the fire hose stream transmitting their energy to
the upper surface of the pool (horizontal component of water stream). A fire hose
stream nearly parallel to the water's surface creates the highest velocity surface
currents and a stream directed vertically into the pool produces minimum surface
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currtr'Tv " . '. '' • 3 Dv >irt
almost . ,N ' ------ ^- -i-,_-}' - -ose stream is removed !ro:n
the point of : -< :. r~ '. oc ,' a, >r , ^ r , . c , <^st important for this report
was the sui fctv_e cut.cTit p:oduced by r:sjng Du^L^i uf air which are entrained in the
water column by the impact of trie lire hose stream on the pool surface (vertical
component of water stream). Air will be entrained to a minimum depth with a Ire
'nose stream directed nearly parallel to the pooi surface while air will be entrained tc a
maximum depth with the stream directed vertically into the water. Such a surface
current will continue to be produced after the fire hose stream is removed due to the
many small bubbles which were driven into the water column and rise very slowly. The
resulting low velocity, enduring current can control an oil slick for a while after the
water jet has moved on. The length of time the current exists depends upon the
amount of air entrained and the depth to which it was driven. The tests at OHM SETT
indicate that a strong jet can produce a current which can endure for more than 60
seconds.
There are two primary phenomena which contribute to the success of a water
jet (Figure 1). The first (Phase 1) is the current initiated by the the outward splatter
of the water stream when it contacts the body of water. This action is instrumental in
preventing oil from being hit by the water jet and subsequently entrained into the
water column. A moving jet creates a slight elevation in water level directly in front
of the impact point. The outward splatter and slight surface elevation combine to
create a mechanism which parts an oil slick directly forward of the impact point of a
moving water jet. The second phenomenon (Phase II) is produced by the air which is
entrained in the water by the jet (Figure 2). A current is produced by the rising
bubbles, which displace water from on top of them and draw water with them as they
travel to the surface. When they reach the surface, they push the last layer of water
out of the way and then burst. The water following the bubble continues to the
surface and dissipates radially. The larger bubbles rise first and fastest and produce a
strong initial current. The smaller bubbles rise slowly and maintain the surface
current even after the water jet has been removed from the area. A turbulent
interaction between jet and water body is important to produce a large number of
small bubbles in order to maintain the oil slick in a desired location (Figure 3). A
stationary water jet will develop a "crater wall" surrounding the impact point due to
the bubbles trying to rise directly up into the jet (Figures 4 and 5).
A third oil moving mechanism is produced only by a moving water jet, or a jet
in a current. This is a wave train of rolling, breaking waves not unlike those produced
by a vertical solid staff towed through a body of water. These waves give an initial
push to the oil by rolling it to the side of the path of the water jet. Each water jet
produces two of these waves. The first is developed as a bow wave originating at the
point of impact. The second is developed at the point where the water surface rises up
behind the jet directly aft of the impact depression (Figure 6). It has been observed
that some oil entrainment results from the turbulence produced by these waves but it
is not much since these waves seldom exceed 2 cm in height. Besides, the rising
bubbles aid in bringing any entrained oil to the surface quickly.
The work presented in this chapter shows the ability of water jets to effectively
move an oil slick in all wave conditions at high speeds without significantly entraining
oil. Although originally intended to prove the feasibility of using water jets to control
oil slicks for testing, the project was expanded to investigate the use of water jets to
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Small currents at various
levels replacing the water
being pushed or pulled to
the surface by the bubbles
e I
Phase I - water flow from
Impact of water stream
o Phase II - rising bubbles
push water aside as they
rise causing a water
current
Figure 1. Section view of water jet action.
5
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A B C
A. As air bubble rises water is pushed from on top and entrained behind,
B. As bubble reaches the surface the last water layer is pushed radially
outward in the surface.
C. As the bubble bursts the water entrained beneath it is carried to the
surface and also radially dissipated.
Figure 2. Single air bubble rising to the water's surface.
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cf.'^V/" ,".'&•- •«-
3&'&£':r?.y
^S^^feJaM....^*. r* :
f^f^. .^j»i-;_^ ^ £^^:>:*^T^i^S
•3- **-- - ~" - ^ • - -—A""- ^**'
,,-,.»• < -.«
'
Figure 3. An underwater view of a time lapse sequence of a
stationary water jet.
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4
I,.-*
jv *. v* v/M 0 \v*^*™^fe.^'f-V '»*'''"'-,-. _s ,"f
"^"' ''" * • '•-
Figure 3. Continued.
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I ' " /' ", * ^ ^ J1 'v"/t '- .* " -' f4 /"T V° 8 - L « ** •**%. %C '^"""3
^^^^'SiLi*£^^!Jit«iLSil
Figure 4. Stationary water jet—side view.
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i^l\~^^'^*^M
Figure 5. Stationary water jet--top view.
10
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p, , .- . - ,'-> <• J < % ' *
t- <"" <••";•>" .'••'*•;*•-• fe'v J * * ?
»'A>J.« \.*",«,.;,*-sj,.-*-f? - ^* *
* A-;H^->" v-.-^/'.^ir-- -^ ~ -f $
<*W%ft}-3&&t. ^-:\
" • - H , .,»'•;' i., •, • i^-t%f .»• -. ' •. a
:-;c^574va:!t^--^
- v—Tons*! :«"35i<.t«L*';«""';
''''i
Figure 6. Moving water jet exhibiting characteristic wave train
11
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converge a wide, thin slick into a narrow, thick one. Problems encountered by trying
to use fabric oil boorn to converge oil slicks during recovery operations have proved it
to be an expensive and low speed operation. If water jets could be substituted for the
boom the operation could be simplified and sped up.
CONCLUSIONS
Vertically directed water jets proved capable of moving and restraining an oil
slick on the surface of water at speeds up to 6 kt and in wave conditions (up to 1.2 m
wave h:-;^ht).
su'Tace, a re;at;veiy nigh current and tnick oil S..JCK neec be present &eiore a
substantial amount of oil can penetrate the crater produced by the jet and be
entrained beneath the water stream. Very little oil entrainrnent was noticed even with
the thickest slick (5 mm) tested at a tow speed of six knots.
Trie bow waves produced by the passage of the water jet helped to move the oil
initially. Some oil is entrained by the bow waves and wake produced by the jet, but
the oil remains near the surface and rises quickly as it is moved with the currents
produced by the rising bubbles.
When converging an oil slick, sufficient time must be allowed after the water
jet passes an area to enable the surface current to fully develop and to move the oil
slick before an oil skimmer can most effectively encounter the thickened slick. This
could be anywhere from 3 to 60 seconds depending upon the desired convergence.
Three millimeter thick oil slicks were not moved as easily as 1-mrn thin oil
slicks.
The best performance of the converging water jet arrangement was obtained
using two and three pairs of jets at a high pressure. At six knots a 4.5 m wide, 1.08
rnm thick slick was converged to a 0.6 m wide, 8.1 mm thick slick in 10 seconds.
These results are most probably not the maximum attainable using three pairs of jets.
Since the first pair of jets were positioned wide and forward of the oil slick their full
effectiveness was not utilized.
From the single jet tests it was found that the most effective performance
occurred at the highest pressures with the largest nozzle at low tow speeds and at a
nozzle exit height of 0.4 to 1.0 m above the water's surface.
The water jet system performed well and was free from major breakdowns
throughout the test program. However, a slight burr on the inside of a nozzle could
cause the water stream to lose coherence and spray more. The penetrating and air
entraining power of the jet is thus diminished and subsequently oil slick movement
performance decreases. Pipes and nozzles should be checked for imperfections and
rocks and other foreign matter should be removed from the hoses before assembly.
12
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Given the problems encountered with the other methods of controlling an oil
slick for test purposes at OHMSETT, it is recommended that water jets be used until a
better method is found.
Prior to employing a water jet system to move oil on water the system should
be examined for burrs on the insides of the nozzles and foreign objects (e.g., small
rocks) in the piping. Any flow disturbance decreases the jet efficiency.
Methods to increase air entrainr/ient by the jets should be investigated.
TEST DESCRIPTION
> en t
The equipment set up for the first test series (slick convergence) consisted of
three pairs of nozzles mounted on the main bridge so as to direct a stream of water
straight down into the water for maximum air entrainrnent (Figure 7). The nozzles
were 20 cm long, 1.6 cm ID bronze pipe nipples cut and trimmed to present a clean,
squared exit for minimum water stream spread.
The first pair of nozzles (No. 1 and 2) were placed on either side of the 4.5 m
distribution manifold each 0.75 m outboard and 0.75 m upstream from the distribution
manifold. The purpose of the upstream placement was to ensure a minimum of
entrainrnent of the Circo 4X light oil used throughout the entire test series. Since this
was the first of a series of tests, it was not known that the jets could have been
positioned closer to the slick without causing severe entrainrnent. The light oil was
chosen due to its low viscosity which allows it to spread faster than any other oil used
in the standardized test procedures of OHMSETT (Appendix B).
The second pair of nozzles (No. 3 and 4) were placed 3.6 m north (downstream)
of the first pair and 4.5 m apart. A third pair of nozzles (No. 5 and 6) were deployed
from the north side (downstream) side of the main bridge 4.5 m apart and 3.8 m
downstream from the second pair of jets. All jet nozzle exits were positioned 1.8 m
above the water surface.
Markers were trailed in the water at 15 and 30 rn from the oil distribution point
for reference locations (Figure 8). At 15 rn a length of small diameter conduit with
streamers tied every 0.3 m was suspended above the water's surface to serve as a slick
width reference device. At 30 m two floats, 4.5 m apart, were trailed from the
auxiliary bridge. A Polaroid camera mounted on the auxiliary bridge recorded the
slick width at both marker locations.
Water to the jets and oil for the slick were delivered by standard OHMSETT
equipment. The pump used to supply water to the jets was the main bridge fire pump.
This pump is capable of delivering 111 m^/hr at 700 kPa. A maximum pressure of 420
kPa could be obtained with all six jets in operations. The oil distribution system used
-------
6 m
,-J
Pump
II Oil L-
! ! Storage If I I
"J|'pi n
rV ! i
L :aif~_J3 ™
Distribution f
J Oil _
! Storaqei
B ridge
, i
cm Poly Rope
Ol! distribution
Test director
Test engineer
jPump operator
jPhotoqraoher
Pressure qauqe
Water jet location
Video Truss
P Tow
Direction
onduit
1 cm Poly Rope Streamers
9 m
"tram era"
Auxiliary
BYidge
i!
m
Floats
15m
15 m
,j]_
nil
Figure 7. Test set up for oi! slick convergence tests.
-------
Main Bridqe
Auxiliary Bridge
Oil
Distribution
Manifold
Second Pair of
Water Jets
Third Pair of
Water Jets
Figure 8. Section view of convergence test set up.
-------
was a ^.5 rn wide, three section manifold with splashpiate and laxdown T. •,=•;• j"Aie
utIJized in many of the tests conducted at OKMSETT to date.
The second series of tests used one nozzle mounted in the center of the north
side of the main bridge to split an oil slick (Figures 9 and 10). This test was designed
to eliminate confusion caused by interferences to slick movement such as wind and
opposing currents generated by other water jets. The same water pump was used as in
the previous tests. With only one nozzle being used 560 kPa of pressure could be
developed. Both 2.1 cm and 2.7 cm diameter nozzles were tested to compare the
relative effect on oil slick movement. The nozzle height was fixed at 0.8 m above the
water's surface. Two small wooden beams were assembled at right a~ gles to each
ether to form a sighting Tool (Figure 11) to monitor the oil slick movement. The lower
piece was held against a rail which ran the length of the main bridge while the
operator sighted oversights on the upper piece at the edge of the oil slick. The
location of this inside edge of the parted slick was thus tracked.
The test arrangement for the third series of tests was like that of the second
series but added the ability to change the height of the nozzle from the water's
surface. A 2.1 cm ID nozzle was used for these water jet tests and also for one test
using compressed air released beneath the water's surface.
TEST PROCEDURES
The tests were so arranged as to determine the effects that various parameters
have upon oil slick movement. The independent variables consisted of tow speed, wave
condition, number of water jets, water jet pressure, nozzle size and height above the
water, and oil slick thickness. The dependent variable was oil slick movement.
The tests conducted for the convergence tests were run according to the test
matrix (Table 1). Basically the tests consisted of the following:
1. Control tests in which a 4.5 m wide slick of 1,2, and 3 mm was deployed
at 2, 4, and 6 knots to check the actual spread of the oil without water
jets.
2. Tests with 2, 4, and 6 water jet nozzles used at different tow speeds and
pressures on oil slicks of different thicknesses.
Preparations for a test run consisted of setting the oil flow to the rate needed
for a particular slick thickness at the test speed, placing in operation the desired
number of nozzles and adjusting valves to obtain the desired water pressure. The
bridge was then brought up to speed and oil distribution begun. When the slick reached
the 15 m marker the first picture was taken. The bridge speed was maintained while
the photographer swiveled the camera for a shot of the slick at the 30 m marker.
After the second photo was taken, the oil distribution was stopped, the fire pump was
secured, and the bridge was brought to a stop. The skimmer booms were lowered to
skim the oil back to the north end of the tank. The photographs taken during a test
were examined and data recorded during the time the oil was skimmed.
The nature of the second and third test series necessitated that other matrices
(Tables 2 and 3) and test procedures be developed. It was necessary to continuously
16
-------
.ii JP "anifo!d
I d a e
Slick Ssghtinq
Tools
1 Test engineer
2 Test director
3 Oil distributor
U Oil slick siqhter
5 Oil slick sighte
A.u xj Ij a_ry_ _B rjd ge
Figure 9. Test set up for single water jet test, slick parting tests.
17
-------
— Main Bridge
91 cm I-b earn
5 cm
40 cm
2.5 cm or
80 cm
Figure 10. Water jet nozzle mounted on the main bridge.
18
-------
Figure 11. M.G. Johnson holding an OHMSETT oil slick sighter.
19
-------
TABLE 1. MAT-I- - ~- ^'.i >' CONVERGENCE TESTS
Test
no.
1
2
3
^
5
6
7
8
9
10
i!
12
13
1*
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
Tow
s Deed
(kts)
2
4
6
2
4
6
2
4
6
2
4
6
2
4
6
2
4
6
2
2
2
4
4
4
6
6
6
2
2
2
4
if
if
6
6
6
if
if
if
if
if
if
4
Slick
thk.
(mm)
1.0
1.0
• i.o
2.G
2.0
": H
/. . u
3.0
3.0
3.0
1.0
1.0
1.0
2.0
2.0
2.0
3.0
3.0
3.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
2.0
2.0
2.0
Number
of nozzles
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
if
6
2
if
6
2
if
6
2
if
6
2
if
6
2
if
6
6
6
6
6
6
6
6
Pressure
CkPa)
0
0
0
0
0
r,
U
0
0
0
0
0
0
0
0
0
0
0
0
70
70
70
1*0
140
140
280
280
280
70
70
70
140
140
140
280
280
280
70
280
420
70
140
280
420
Calm
Calm
CaJm
Cairn
Calm
CaJm
Calm
Calm
Calm
0,6 m HC
r, /•' „_, i) '•
u * c i Fi n \^
0.6 IT, HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
0.6 m HC
Calm
Calm
Calm
Calm
Calm
Calm
Calm
20
-------
TABLE 2. MATRIX FOR SLICK DIVERGENCE TESTS
Test
no.
i
2
3
k
5
6
7
8
9
10
11
12
13
1*
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Tow
speed
(kts)
2 to 6
2
2
2
4
4
4
6
6
6
2
2
2
4
14
4
6
6
6
2 to 6
2
4
6
2 to 6
2
4
6
2 to 6
2
4
6
2
4
6
SJick
thk.
(mm)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
3.0
3.0
3.0
3.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Nozzle
I.D. (cm)
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7 .
2.7
Pressure
kPa
0
140
280
560
140
280
560
140
280
560
140
280
560
140
280
560
140
280
560
0
280
280
280
0
560
560
560
0
280
280
280
560
560
560
Wave
(mm)
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
0.5x12.1
0.5x12.1
0.5x12.1
0.5x12.1
1.2 m HC
1.2 m HC
1.2 m HC
1.2m HC
1.2 m HC
1.2 m HC
1.2 m HC
21
-------
TABLE 3. TEST MATRIX FOR WATER 3ET HEIGHT EFFECTS
Test
no.
Tow
speed
(kts)
Nozzle
I.D.
(cm)
Pressure
(kPa)
Slick
thk.
(mm)
Nozzle
height
(m)
Wave
1
2
3
u
5
6
14
6
14
6
2.1
2.1
2.1
2.1
2.1
2.1
560
560
560
560
560
560
.0
.0
1.0
1.0
1.0
1.0
0.6
1.8
1.8
0.6
0.3
0.3
Calm
Cairn
Calm
Cairn
Calm
Calm
22
-------
:he oij s'ick. Towing markers was impractical because the
slick was to be observed for one ;n inure and a large number of markers would have
been needed. Besides, the n;arkers would have been too far from the bridge to be
photographed well. Time constraints prevented gridding the tank with small anchored
floats to be used a references. The slick was monitored using the sirnpjy constructed
sighting apparatus described earlier. Two sighting boards were slid along the rail on
the main bridge until the operators v.ere lined up with the inside edge of the slick they
were following. Every 15 seconds, for one minute, a position reading was taken from
both of the sight board operators. The water jet nozzle was mounted in the center of
the main bridge so the readings indicated how far the slick was split on either side of
the jet. The original test plan was designed to move the water jet down one side of
the oil slick, but wind would have biased the 'eacings.
DISCUSSION OF RESULTS
The tests were successful in revealing how the independent parameters tested
effect water jet performance. The graphs presented herein were developed from the
tabulated test results (Tables 4, 5, and 6). Direct comparison of slick movement
between the convergence tests and oil slick parting tests is difficult. Oil movement in
the convergency tests was less than that recorded during the slick parting tests due to
the opposing currents developed by the pairs of jets and the build up of oil between
them. Other causes for the different results were the longer pipe nozzles used in the
slick parting tests and the difference in height from the water of the nozzles. The
longer pipe (length greater than 15 ID) resulted in a more coherent water stream being
delivered. Such a water stream entrained air well without the jet splattering onto the
oil slick and thereby entraining oil. A coherent water jet of the size and at the
pressure tested performed best at a height of 0.^ to 1.0 m above the water's surface.
The parting slick tests had the nozzle heights within this preferred range while the
convergence slick tests had nozzle heights above 1.0 m. However, general effects of
the independent variables can be qualitatively compared between the tests. In this
regard the convergent and divergent tests can be discussed together. The graphs
which depict the effects of the parameters are clearly labeled as to which tests they
pertain to.
The oil slick sighters were tested against known widths of 5 m over a 30 m
distance and resulted in accuracy within 0.3 m. Data for the slick convergence tests
were taken from Polaroid pictures. The accuracy of this method was about the same.
The effects of the independent parameters on oil slick movement are discussed
individually.
Tow Speed
The time required to part a slick a given distance was inversely proportional to
the tow speed using the same water jet, (Figure 12). If a water jet parted a slick 3 m
in 15 seconds when run at 2 kts, the same jet would require 30 seconds to part the slick
3 m at ^ kts. This generally held for the slick convergence tests until interaction
occurred between the jets on either side of the slick (Figure 13). Such a relationship
would probably break down for smaller water jets and faster tow speeds. Surface
tension effects would probably cause a small water jet to splatter somewhat upon
impact rather than penetrate and entrain air.
23
-------
TABLE 4A. CONTROL TESTS, 29 AUGUST 1978, CALM WATER (SLICK CONVERGENCE TESTS)
K)
Test
no.
31
32
33
34
35
36
36R
37
38
39
39R
Speed
(kts)
2
it
6
2
*
6
6
2
4
6
6
Slick
thick
(30m
(mm)
i.
i.
0.
2.
2.
2.
2.
3.
3.
3.
3.
21
20
95
40
16
16
21
24
29
09
12
Slick
width
@15m
(m)
4.
4.
4.
5.
5.
5.
6.
6.
6.
6.
8
8
8
75
45
15
06
06
06
06
Slick
width % Expan
(B30 m (315 m
(m)
6.06
5.75
5.15
6.66
6.06
5.45
7.27
6.96
6.36
6.36
7
7
7
27
20
CAMERA MALFUNC'I
13
33
33
33
33
Slick
% Expan thick
@30 m @15rn
(rnm)
33
27
13
47
33
'ION
17
60
53
40
40
i
1
0
i
1
1
2
2
2
2
.13
.13
.89
.89
.80
.95
.43
.47
.32
.34
Slick
thick
(§30 m
(mm)
0.91
0.95
0.84
1.64
1.62
1.84
2.03
2.15
2.21
2.23
-------
TABLE 4B. CONTROL TESTS, 31 AUGUST 1978, 0.6 m HARBOR CHOP (5L
NJ
U1
Test
no.
40
41
i+2
43
44
1+5
46
47
48
Speed
(kts)
2
'4
6
2
4
6
2
4
6
Slick
thick
(90m
(mm)
1.27
1.02
0.97
2.04
1.62
2.11
3.23
3.18
3.62
Slick
width
@15 m
(m)
5.15
4.8
4.8
5.15
4.54
6.06
6.66
5.75
4.8
Slick
width
(d30 m
(m)
5.75
5.15
4.8
5.45
6.66
5.45
6.06
6.66
4.8
% Expan
(315 m
13
7
7
13
0
33
47
27
7
% Expan
(330 m
27
13
7
20
47
20
33
47
7
Slick
thick
(d!5 m
(mm)
1.12
0.96
0.91
1.80
1.62
1.58
2.20
2.51
3.39
Slick
thick
(§30 m
(inrn)
1.00
0.90
0.91
1.70
1. 10
1.76
2.42
2.17
3.39
-------
TABLE *C. WATER 3ET TESTS, 30 AUGUST 1978, CALM WATER (SLICK CONVERGENCE TESTS)
NJ
01
Test
no.
1
2
3
>t
5
6
7
8
9
10
li
14
16
Speed
(kts)
2
2
2
'4
*
*
6
6
6
6
*
2
2
Slick
thick
(90 m
(mm)
1.1*
1.19
1.09
1.09
1.0*
1.15
1.16
1.08
1.01
1.11
1.03
0.92
1.11
Slick
width
(915 m
(m)
3.63
1.5
1.51
3.63
2.72
2.42
3.63
2.42
2.72
3.03
1.21
0.90
3.03
Slick
width
(930 m
(m)
2.72
2.12
1.81
3.33
1.51
0.90
2.72
0.60
0.90
2.72
0.90
2.72
2.72
Slick
thick
(§15 m
(mm)
l.*3
3.57
3.27
1.36
1.73
2.16
l.*5
2.03
1.68
1.67
3.86
4.60
1.67
Slick
thick
(315 m
(m m )
1.90
2.53
2.73
1.^9
3.12
5.75
1.93
8. JO
5.05
1.85
5.15
1.53
1.85
Number
of
nozzles
2
*
6
2
*
6
2
'f
6
2
?f.
6
2
Water
press.
(kPa)
70
70
70
1*0
1*0
1*0
280
280
280
560
560
*20
1*0
-------
TABLE 4D. WATER JET TESTS, 31 AUGUST 1978, 0.6 m HARBOR CHOP (SUCK_CONVERGENC1^TESTS)_
Test
no.
16
17
18
19
20
21
22
23
24
Speed
(kts)
2
2
2
it
14
4
6
6
6
Slick
thick
@0 m
(mm)
1.13
1.13
1.16
1.08
1.17
1.17
0.95
1.23
1.16
Slick
width
@15 m
(m)
3.63
1.81
2.12
3.93
2.42
2.42
3.93
2.72
2.42
Slick
width
(930 m
(m)
3.03
1.81
1.51
3.63
1.51
1.21
3.33
0.90
1.81
Slick
thick
@15 m
(mm)
1.41
2.82
2.49
1.25
2.19
2.19
1.09
2.05
2.18
Slick
thick
@15 in
(m m )
1.70
2.82
3.48
1.35
3.51
4.39
1.30
6.15
2.89
Number
of
nozzles
2
4
6
2
4
6
2
4
6
Water
press.
(kPa)
70
70
70
140
140
140
280
280
280
-------
NJ
00
TABLE 4E. WATER JET TESTS, 1 SEPTEMBER 1978, CALM WATER (SLICK CONVIIR_^EN_Ci3_TESTS)
Test
no.
49
50
41
52
53
55
Slick
Speed thick
(kts) (§0 m
(mm)
4 1.05
4 1.08
4 1.05
4 2.26
4 2.21
4 2.26
Slick
width
@15 m
(m)
2.72
2.12
1.51
3.03
2.42
2.12
Slick
width
@30 rn
(m)
1.81
0.90
0.90
1.81
1.51
1.51
Slick
thick
@15 m
(mm)
1.5
2.31
3.15
3.39
4.14
4.84
Slick
thick
(ci 1 .5 1 1 1
(mm)
2.63
5.40
"5.25
5.65
6.63
6.78
Number
of
nozzles
6
6
6
6
6
6
Water
press.
(kPa)
70
280
420
70
280
420
TABLE 4F. WATER 3ET TESTS, 1 SEPTEMBER 1978, 1.2 m HARBOR CHOP (SLICK CONVERGENCE_TESTS)
Test
no.
56
57
58
Speed
(kts)
4
4
4
Slick
thick
@0 m
(mm)
1.25
6.23
6.23
Slick
width
@15 m
(m)
1.81
2.42
2.42
Slick
width
@30 m
(m)
1.51
2.72
2.12
Slick
thick
@15 m
(mm)
3.13
11.68
11.68
Slick
tiuck
(ci30 m
(in m )
3.75
10.38
13.35
Number Water
of press.
nozzles (kPa)
6
4
4
560
280
560
-------
TABLE 5. SINGLE 3ET TEST RESULTS (SLICK PARTING TESTS),
N)
U5
'""'•" ' ' ' •— ' -
Test
no.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
2>4
25
26
27
28
29
30
Tow
speed
(kts)
2
2
2
2
*
*
4
6
6
6
2
2
2
*
4
*
6
6
6
2
*
6
2
4
Nozzle
ID
(cm)
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.7
2.7
, 2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
Slick
thick
(mm)
0.9
1.2
1.2
1.2
0.8
1.0
1.1
1.0
1.0
1.0
1.4
1.2
1.2
1.2
1.2
1.2
1.0
0.9
1.1
2.7
4.8
3.3
1.4
1.1
Water
press
(kPa)
140
280
560
0
140
280
560
140
280
560
140
280
560
140
280
560
140
280
560
280
280
280
560
560
Wave
Calm
Calm
Cairn
Calm
CaJm
Calm
Calm
Calm
Calm
CaJm
Calm
Calm
Cairn
Calm
Cairn
Calm
Calm
Calm
CaJm
Cairn
Cairn
Cairn
15
2.4
2.7
3.4
7.6
2.0
2.2
2.2
i . 3
i.S
2, I
7,7
2.8
4.2
j.8
2.4
2.7
2.0
2.1
2.7
3.0
3.6
2.4
Elapsed Time (sec)
30 45
Slick Movement (m)
2.8
3.4
4.2
8.0
2.4
2.6
3.0
1.8
2.3
2.6
3.5
3.6
5.1
2.6
2.9
3.5
2.6
2.8
3.2
4.5
3.9
3.6
3.1
3.8
4.5
8.5
2.4
2.9
3.8
2.3
2.7
3.0
3.8
4.2
5.4
3.0
3.6
4.4
2.9
3.5
3.8
5.0
4.8
4.2
60
3.4
4.0
4.8
8.8
2.6
3. I
4.5
2.5
2.9
3.1
4.i
4. 5
5.7
3.2
4.5
5. J
3.2
3.9
3.9
5.4
3.5
3 . 4
5.8
4.7
(Continued)
-------
TABLE 5. (Continued)
Test
no.
31
32
33
34
35
36
37
26R
21R
22R
Tow
speed
(kts)
6
2
4
4
2
6
6
2
4
4
Nozzle
ID
(cm)
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
Slick
thick
(mm)
0.7
1.3
0.7
1.1
1.3
0.9
0.9
3.5
1.1
0.9
Water
press
(kPa)
560
280
560
280
560
280
560
280
280
560
Elapsed Time (sec)
Wave 15 30 45
Slick Movement (m)
2.3 3.3 3.6
1.2HC 2.1 3.0 3.9
I.2HC 3.0 4.2 5.2
1.2HC 2.1 3.3 3.5
1.2HC
1.2HC
1.2HC
Calm
Calm
Calm
60
14,2
4.5
4.9
3.7
6.1
2.7
4.r,
4.2
3.6
4.8
U)
o
-------
TABLE 6. WATER 3ET HEIGHT EFFECTS TEST RESULTS (SUCK PART
TESTS)
Test
no .
i
2
3
14
5
6
7
8
9*
Tow
speed
(kts)
4
6
6
it
4 to 6
* to 6
4
6
*
Nozzle
ID
(cm)
2.1
2.1
2.1
2.1
Observation
Observation
2.1
2.1
2.1
Height
of exit
above
(m)
0.
0.
1.
1.
run
run
0.
0.
-0.
water
6
6
2
2
3
3
6
Slick
thick
(mm)
3
3
3
3
3
3
3
Water
press.
(kPa)
560
560
560
560
560
560
210
.., „
Wave
(in)
Cairn
Calm
Calm
Calm
Ca 1 m
Cairn
Calm
Cairn
Calm
2
2
1
1
2
2
2
1
10
.if
.3
.6
.0
.7
.6
.7
l:lapsed Time (sec)
20 30
Slick Movement (m)
3.2
2.8
2.2
3.0
2.9
2.6
1.7
3.9
3.4
2.5
3.3
3.4
2.8
1.9
3.6
2.8
3.5
3.6
3.1
2.0
*Test run with 210 kPa of pressurized air being fed through a 2.1 cm ID pipe extended 0.6 m below the water's surface.
-------
00
NJ
s
L
I
D
K
M
0
V
E
M
E
N
T
I
N
M
E
T
E
R
S
A- 2 KTS
D- 4 KTS
0-6 KTS
-A
..0
1 -
0
38
TIME CSECONDS)
45
60
Figure 12, Effect of tow speed on oil slick movement - 1-mm slick, calm water, 2.1-cm ID nozzle at 560
Kpa (slick parting tests).
-------
s
L
I
C
K
W
I
D
T
H
I
H
M
E
T
E
R
S
A-
Q~
0-
2 KTS., H0 KPa, 2
4 KTS., 140 KPa, 2 JETS
4 KTS., 288 KPa, 2
6 KTS., 280 KPa, 2 JETS
10 15 28
DISTANCE FROM DISTRIBUTION POINT CMEIERS)
_l
25
„. i
30
Figure 13. Effect of tow speed on oil slick movement - 1~mm slick thickness, cairn water, 2.1-cm ID
nozzles (slick convergence tests).
-------
Non-breaking waves appeared to have little or no effect on water jet perform-
ance (Figures 14 and 15). Inherent difficulties in distributing a uniform slick onto a
harbor chop sea state resulted in oil slick width variations. Such variations can
account for the relatively minor deviations of the harbor chop results from the calm
water results.
Trie results declare that the more water jets that are employed, the greater the
control of the oil slick (Fiure 16). This is reasonable since surface current controls
te o sc an trie more water ets n
produced. Since the slick parting tests used only one nozzle in the tests there is no
graph from those tests to illustrate this point.
eTr essure
The greater the water jet pressure the greater the control over the oil slick
(Figures 17 and 18). However, in the convergence tests there was a point of
diminishing returns. For the first 15 m in the 6 nozzle case at 4 knots, 140 kPa
pressure was sufficient to move the oil slick from 62 to 88 percent of the distance that
water jets using 420 kPa moved the slick. For the second 15 m, 140 kPa moved the
slick 100% of the distance moved using 420 kPa. When using only two nozzles the
higher possible pressures resulted in greater slick control over the entire observation
time (Figure 16). These tests also showed that a converged slick will spread again
quickly once the currents produced by the two water jets subside.
Slick Thickness
The slick convergence tests showed consistently that the thicker the oil slick,
the more difficult it is to move (Figure 19). With the arrangement of water jets
tested, a 4.5 m wide oil slick of 1 to 2 mm thick could be thickened to 5 to 6 mm, (3 to
5 times as thick). The spreading forces of the oil and jet interaction appear to limit
convergence and thickening of an oil slick beyond this. A thicker slick of 6.23 mm was
driven to a 13.35 mm thickness. However, this is a reduction of width and an increase
in slick thickness of only a factor of 2.14. The slick parting tests were not as
consistent with their results (Figure 20). Some tests turned in higher performance in a
thicker slick while others delivered the expected poorer performance. Since a thicker
oil slick spreads faster than a thin slick, parting a heavy slick should be more difficult
than parting a thin slick. The better performance in heavy slicks is probably an
abnormality in the data caused by wind and/or errors in slick sighting.
Nozzle Size
The larger the nozzle the better the performance at the same pressure. The 2.7
cm ID nozzle outperformed the 2.1 cm ID nozzle at all speeds tested. A typical
comparison is presented for the four knot tests (Figure 21). This result is logical since
more water will flow through a larger pipe than a smaller pipe for a given pressure. A
greater fluid flow should be expected to entrain more air and thus create a stronger
surface current.
-------
w
I
D
T
H
I
N
M
E
f
I
E
R
A
F
T
E
R
3
8
S
E
C
A- CALM WATER
D- 8.6 H HC WAVE
SLICK WIDTH AT OIL DISTRIBUTION POINT
L
8
• 8
Q
l_
234
NUMBER OF NOZZLES USED
5
6
,£ 1'K.^ater Jef Performance.. in 'calm water and waves - 1-mm slick,
kPa (slick convergence tests).
kt, 2.1^cm ID nozzle at
«"•« «i
-------
s
L
1
C
K
M
0
V
E
"if
E
N
T
I
N
M
E
T
E
R
S
7 h
6 -
A- CALM WATER, 580 KPa
D- 0.3 H HC, 580 KPa
<>- 0.7 H HC, 280 KPa
+ -0.6 H RES, 560 KPa
°~ CALM, 280 KPa
4 L
30
TIME CSECONDS)
45
68
Figure 15. Water jet performance in calm water and waves - 1-mm slick, 2.6 cm ID nozzle U kt (slick
parting tests). . '
-------
s
L
I
C
K
W
1
D
T
H
I
N
E
T
E
R
S
A- 8 NOZZLES
D- 2 NOZZLES
0-4 NOZZLES
f- 6 NOZZLES
:SLICK WIDTH AT OIL DISTRIBUTION POINT
RESPREAD1NG OF THE SLICK
18 15 28
DISTANCE FROM DISTRIBUTION POINT
CM)
Figure 16. Effect of the number of water jets on oil slick movement - 1-mm slick, 2 kt 1 6-cm ID
nozzle at 70 kPa (slick convergence tests).
-------
Ul
CD
0
A - 0 NOZZLES
D~ 78 KPa
KPa
SLICK WIDTH AT OIL DISTRIBUTION POINT
OF THE SLICK
10
DISTANCE
15
FROH DISTRIBUTION
28
POINT
30
CM>
Figure 17. Effect of water jet pressure on oil slick movement - 2 kt, 1-mm slick, 2 nozzles, 1.6-cm ID
nozzles (slick convergence tests).
-------
U)
(JO
s
L
I
C
K
M
0
V
E
M
E
N
T
I
N
M
E
T
E
R
S
A_ 148 KPa
D- 288 KPa
0» 568 KPa
•-A
0
15
38
TIME CSECONDS)
60
Figure 18. Effect of water jet pressure on oil movement - 2 kt, 1 -mm slick, 2. 1 cm ID nozzle (slick
parting tests).
-------
s
L
I
C
K
W
I
D
T
H
N
M
E
T
E
R
S
A- 1 MM, AFTER 15 SECS, CALM
D- 1 MM, AFTER 7.5 SECS, CALM
0- 2.2 MM, AFTER 15 SECS,
•f- 2.2 M, AFTER 7.5 SECS, CALM
0- 6.23 MM, AFTER 7.5 1.2 M HC
SLICK WIDTH AT OIL DISTRIBUTION POINT
8
50
180 158 280 258
WATER JET PRESSURE CKPeO
388
350
408
Figure 19. Effect of water jet pressure and slick thickness on oil slick movement 4 kt, 6 nozzles
cm ID nozzles (slick convergence tests).
-1.6-
-------
s
L
I
C
K
M
0
V
E
M
E
N
T
1
N
E
T
E
R
S
A_ ! MM, 288 KPa, 2 KTS
D-2.7 MM, 280 KPa, 2 KTS
0- i MM, 280 KPa, 6 KTS
-3.3 MM, 280 KPa, 6 KTS
* UNUSUAL RESULT SINCE THE THICKER SLICKS SHOULD
MORE DIFFICULT TO MOVE.
38
TIME CSECONDS)
Figure 20. Effect of slick thickness on oil slick movement - 2.1-cm ID nozzle (slick parting tests).
-------
4=
K)
s
L
I
C
K
M
0
V
E
M
E
N
T
I
N
M
E
T
E
R
S
A-
D-
0-
568 Kpa, 2.7cm ID NOZZLE
560 Kpa, 2.1cm ID NOZZLE
140 Kpa, 2.7cm ID NOZZLE
148 Kpa, 2.1cm ID NOZZLE
4 I-
38
TIME CSECONDS)
Figure 21. Effect of nozzle diameter on oil slick movement in calm water, 1-mm slick H kt fslick
parting tests).
-------
Nozzle Heijght
The best performance was achieved when the nozzle exit was 0.4 to 1.0 m
above the water's surface (Figure 22). Above the optimum height the water stream
was given a chance to spread and it lost its coherence. Penetration was reduced and
thus the amount of air entrained was reduced. Below the optimum height the jet did
not have enough time to fully develop the turbulent boundary layer which transported
air along with it into the receiving water. The result was the same as having the
nozzle too high—less air was entrained into the water column and thus less surface
current was produced. The crater which served to prevent oil from getting beneath
the jet was also reduced in both cases and more oil entrainment resulted. This result
may not hold true for other types of nozzles or water pressures not in the range
tested.
The waves produced by a moving jet were observed to entrain oil to a maximum
depth of about 15 cm. The oil rose quickly to the surface as it moved away from the
point of impact. The jet was recorded to entrain air to beyond 1 meter depth. No oil
was seen to be entrained to such depths. This gave good evidence to the effectiveness
of the crater to part the oil slick and keep it from beneath the water jet. The rapid
rise of the wave entrained oil to the surface was probably the result of the small
bubbles of air entrained by the jet rising into the oil droplets and making them more
buoyant.
A nomograph was developed from the results of the convergence tests (Figure
23). It is used to determine the size and number of water jets and the water pressure
to the jets necessary to converge a 1 mm oil slick at four knots. A different
arrangement of water jets would render a different nomograph.
To use the nomograph one must decide how wide of a slick (e.g. 3 rn) is to be
converged to the necessary width (e.g. J m). A straight line is drawn between the two
widths. The number of nozzles (4) and the pressure necessary (90 kPa) is read from the
scales.
A test run was carried out using a submerged pipe discharging compressed air to
part an oil slick. A 50 Kw, gasoline engine air compressor supplied the 2.0 cm ID pipe
with 210 kPa air pressure. The tests were run at four knots and calm water through a
1 mm slick. The results showed a very clean path cut through the oil, but the oil slick
movement was significantly less than that produced by a 2.1 cm ID water jet at 140
kPa water pressure (Figure 24). During tank cleanup one day, a 6.1 cm ID hose
connected to a 225 Kw, 1250 m^/hr air compressor was used to move oil away from a
tank wall. The air pressure was approximately 560 kPa pressure. The air was directed
at the oil slick from above and it was also submerged to bubble up air. In all
configurations attempted, the compressed air source could not match the oil slick
movement capability of a single 2.1 cm ID fire hose at approximately 420 kPa water
pressure. The power required to drive the fire hose was about 20 Kw.
43
-------
s
L
I
C
K
M
0
V
E
H
E
N
T
6
NOZZLE
HEIGHT
A- 8.6 H,
D- 8.6 M,
0- 1 .2 M,
+ - ! .2 H,
0- 0.3 H,
• - 0.3 M,
TOW
SPEED
4 KTS,
6 KTS,
4 KTS,
6 KTS,
4 KTS,
6 KTS,
WATER
PRESSURE
ALL AT 568 KPa
X- -8.6 M, COMPRESSED AIR, 4 KTS, 210 KPa
28
TIME CSECONDS)
30
48
Figure 22. Effect of water jet nozzle height on oil slick movement
nozzle (slick parting tests).
1-mm slick, calm water, 2.1-cm ID
-------
Distribution
Slick Width (Meters)
Nozzle
Number
1.58cm ID SCH 40
Nozzle
-4
1.25 en ID SCH 40
Nozzles
— 0.5
Water Jet
Manifold
Pressure (KPa)
• 420
•280
• 140
— 150
Desired Slick
Width at 15 M
•0,5
•70
•35
Figure 23. OHMSETT water jet nomagraph used for converging
a 1~mm slick at 4 kt.
-------
4=
en
Z 7 ~
M
0
V
E
M
E
N
T
1
N
M
E
T
E
R
S
6 »-
8
A- 148 Kpa, WATER JET
D- 280 Kpa, WATER JET
0- 568 Kpa, WATER JET
i- 210 Kpa/ AIR
28
TIHE CSECONDS>
38
48
Figure 24. Comparison of water jet performance to that of a compressed air source, 1-mm slick calm
water, 2.1-cm ID nozzle, (siick parting tests).
-------
SECTION 3
WATER 3ETS MOUNTED ON A MOVING OIL SKIMMER
INTRODUCTION
To have a practical application to large scale oil spill recovery, the water jets
must be able to be mounted and perform well on a moving oil skimmer. Tests
conducted at OHMSETT in this regard were designed to develop an oil converging
system to be incorporated with the U.S. Coast Guard's Zero Relative Velocity (ZRY'j
fast current oil skimmer^ (Figure 25). The objective was TO converge a 6 m wide slick
in to a 2.7 m wide slick (oil skimmer inlet size) at 6 knots in various wave conditions.
Since the principle of the ZRV skimmer consisted of oil absorbtion and adsorbtion onto
a floating composite belt, the oil slick had to be on the surface when it was in the
reduced width. Oil entrained during the slick convergence would not be recovered by
the skimmer.
The test program looked at the ability of a pair of water jets to converge a
slick while mounted on a catamaran and at the entrainment developed by the water
jets. The independent variables of the test were water jet nozzle size, tow speed, oil
slick thickness, wave condition, water pressure, number of water jet nozzles in service
and water jet nozzle attitude. The dependent variables were oil slick movement and
the amount of oil entrainment.
CONCLUSIONS
Water jet booms can be successfully incorporated onto a moving oil skimmer to
converge a wide thin slick into a narrow thick one for easier oil recovery.
Vertically directed jets proved to be the best all-wave performers. Angled jets
performed slightly better than the vertical jets in calm water, but performed
erratically in wave situations. The point of impact of a stream from angled jets and
the distance between the nozzle exit and the point of impact changed drastically when
the long booms on which the jets were mounted reacted to the catamaran's pitch and
heave in waves.
Using the electric motor driven fire pump available on the OHMSETT main
bridge, the best performance at different tow speeds by water jets on the 7.25 m is
presented below:
-------
00
Oil
Pipe Boom
-Water jet nozzle ,.,.;.:.:v;wS ;•;:;•
Figure 25. USCG ZRV skimmer using water jets to sweep oil
-------
Tow
speed
kts
2
*
6
Nozzle
size
cm
2.1
2.1
2.1
Pressure
kPa
210
560
600
Water jet
angle
in/fwd
degrees
0/0
20/0
10/45
Wave
cond.
calm
calm
calm
Orig.
slick
width
m
6.1
0.2
6.1
Final
slick
width
m
1.7
1.1
2.9
Slick
movement
m
4.4
3.2
3.2
Note: Not alJ nozzle sizes were tested at all pressures and tow speeds.
A satisfactory boorr, length ior a water jet off the bow of a skimmer 10 to 15 m
in length appears to be from 6 to 12 m. A longer water jet extension improves
performance in cairn water. However, any pitching and heaving of the vessel is
amplified by the long boom. If the boom is too Jong, vessel movement can cause the
water jet to be raised high above the water's surface and plunged into the water
regularly. Such action renders the water jets ineffective.
The stationary tests revealed that some oil is entrained by a passing water jet,
but that almost all of the oil slick remains on the surface. Oil that is entrained is
carried away from the water jet impact point as it rises to the surface. The angled
jets appeared to entrain more oil.
A pair of water jets can be expected to essentially double the sweep width of
the U.S. Coast Guard's ZRV skimmer from 2.7 to 5.4 rn at speeds up to 4 kts. To
perform as well at 6 kts a longer boom would be required.
RECOMMENDATIONS
Designs of collapsible water jet booms should be investigated. Transportability
and longevity of the booms would be enhanced if they could be folded for storage on
the bow of a skimmer.
Water jet/skimmer tests should be conducted with the skimmer traveling with
the waves to reduce the pitch and heave of the vessel.
The U.S. Coast Guard Zero Relative Velocity Skimmer should be fitted with
water jet booms divided into two 3 m and two 1.5 m sections for each side. A suitable
length boom can then be assembled depending upon skimming operations and sea
conditions.
The water jet boom sections should be stiffened and reinforced to eliminate
whip from the booms when operating in waves and to withstand rough handling. Such
protective construction could be placed inside the boom pipe rather than outside as
was done for the system used in these tests. Using internal reinforcing members would
require special consideration to ensure adequate water flow with minimal pressure
drop.
-------
TEST DESCRIPTION
Test Equipment
The OHMSETT catamaran, IDA m long and 9.1 m wide was mounted with two
vertical stanchions to support the water jet booms. A movable collar was placed at
the base of each stanchion to mount the water jet booms (Figure 26). The water jet
booms were constructed from sections of aluminum pipe welded together. The pipe
served as a structural member and as a conduit for the water used by the jets. The
booms were supported and held in place by 0.32 cm aircraft cable and turnbuckles
(Figure 27). The water jets were constructed as to allow rotation in every piane
(Figure 28). Operators were able to splay the booms to various widths, angle the jets
in towards the centerline of the system and tilt them forward. The waier jet nozzles
were 30 cm Jong standard pipe of various inside diameters (i.e. 1.25, 1.6, 2.1, 2.7 cm).
The nozzles were wrapped with bands of black tape for identification in photographs.
The smallest had one band, the next size had two, the next size had three and the
largest had none.
The catamaran with stanchions and booms was placed in the tank and rigged for
towing by the main bridge (Figure 29). The main bridge fire pump supplied the water
jets via 5 cm diameter hoses. Pressure gauges were mounted along the water jet boom
in order to determine the water pressure close to the water jet outlet.
Oil was distributed from either a manifold or individual outlets located on the
south side of the main bridge. For oil slicks greater than b.5 m in width the individual
outlets were used, otherwise the oil manifold was used. Medium oil (see Appendix B)
was used for these tests since its properties most closely match those of the kind of oil
which the U.S. Coast Guard determined the ZRV skimmer would be recovering in
actual oil spill situations.
To observe the oil entraining properties of a water jet, the catamaran was held
stationary in an oil slick with the water jet nozzle positioned directly above an
underwater window (Figure 30). The boom was swung through an arc by pulling it with
a rope from the video bridge. The rate of swing was calculated to have the water jet
moving at about 4 knots. The action of the water jet impacting the oil and water was
recorded via slow-motion 16 mm movie photography and sequential 35 mm still
photography through the underwater window (Figure 31 A through K). A small
workboat was positioned against the tank wall over the underwater window to prevent
oil from being driven down onto the glass by the water jet. A barrel was positioned on
the tank deck to receive the flow from the water jet prior to the test.
Test Plan
All tests were conducted according to the following test procedures:
1. Prepare appropriate photo/video equipment (shoot test record boards).
2. Prepare oil distribution for tow test or stationary slick.
3. Adjust the water jet nozzle and booms to the appropriate angles.*
50
-------
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p
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m, a*1 ffisJ
?!lLi2R^ac Ji MJi^a',*r >j , _J «aJ».ti >-«.»• «AJji'*-j»-»^
Figure 26. First generation water jet booms
51
-------
in
NJ
iwo sections of reinforced e.iuminum pipe
(10 ft. ep.ch)
OEM8EII C.Vonmaran
Direction of Tow
Water
Jet
Nozzle
Water
Supply
Hoses
Figure 27. Second generation water jets mounted on OHMSET I catamaran,
-------
Vertical
Stanchion
Moveable
Collar
Longitudinal Swivel
Joint
90° Elbow
Ploe Unioi
Water Jet
Nozzle
Figure 28. Details of second generation water jet.
-------
Figure 29. Test set up for oil skimmer/water jet tests.
-------
OH distribution manifold
P0*_i
t
J;
S
1
2
3
4
5
6
Test engineer
Test director
Oil distributor
Boom operator
Photographer
Photographer
Main
Eridqt
6
* - f . L I
|; J 1 1 J: U/W
* • '
Window
OHMSETT
Catamaran
iliarv_ Bridge
55-gaIlon
drum
Water
Jet
Boom
Figure 30. Test set up for stationary tests - pivoting a water jet boom,
55
-------
'£L~. •=-— — - -„ ~—. - -«^««^-^**^i&^»»S?>r:-»^^^S
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Figure 31. Continued.
-------
; ,-•;. :\'Xffl.
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\',- '• r5 '" / ',;" ," " .I,'1', *
Figure 31. Continued.
58
-------
<:':•£$$
•i.-f£"ti'"\™'~'*.33.:?T,^\"':~yxv asr: "n.y
Figure 31. Continued.
59
-------
'
Figure 31. Continued.
60
S,- ,-^- - _--"••• '•• \
V| * " ff' 6 ' "u"--i ' - ', '"^"•Kw , -~ .pf
Oi>viIi»W*i&* ^'tfid^vatofaL •;M^T-!;^/"---\/^ f*_-f;/— -.u-i.f ,»*^,fc*w
-------
*f. Obialn the desired se& state.
5. Start the water pump and bring the water jet to the correct pressure.
6. Alert the photo video department that the test is commencing.
7. In the case of a stationary test the oil slick was distributed, the bridge
horn sounded and the boom swung through the oil slick.
S. In the case of a tow test the bridge horn 'was sounded, the tow begun and
oil distribution begun when the correct tow speed was achieved.
9. At trie conclusion 01 the test run remove the oil from the water's surface
using the skimming boom or fire hoses.
10. Prepare for the next test.
*Consistent sweep widths were maintained for lest comparison purposes. In order to
compensate for the movement of the water jet impact point due to the inward angle of
the nozzle, the boom splay angle was adjusted.
Both tow tests and stationary tests were conducted according to matrices
(Tables 7 and 8) developed by the OHMSETT engineering staff in conjunction with the
US EPA project officer. The results from the tow tests (Table 9) were organized to
clarify the relationship of the independent parameters to the dependent parameters.
The stationary tests were qualitatively analyzed and are commented on later in this
report. Due to time constraints, all of the tests in the original test matrices could not
be run.
The objective of the first pair of water jet booms made was to be from 6 to 12
rn long, strong enough to survive in waves and light enough to be handled and supported
easily. The booms were constructed from 1.8 m sections of 6.^ cm ID standard
aluminum pipe welded together. The first boom failed at a welded point due to the
force of the water inside of it and the guy wire forces outside. The joint was rewelded
and stiffeners were incorporated at each joint to add strength. Stiffeners were not
welded over the entire length of the pipe boom until the next generation of water jet
booms were made. The repaired booms proved able to support themselves and the
water with the aid of the guy wires but they were still too flexible. During tow tests
in the 0.5 m harbor chop, the water jet on the end of the 12 m boom was whipped
between 3 m above the water's surface and 0.5 m below the surface due to vessel
pitch. The flexibility of the boom also caused problems in rigging the booms on the
catamaran since the guy wires supporting the boorns placed loads down the longitudinal
axis of the boom. Any twist of the collar which held the boom to the vertical
stanchion caused a bow to develop in the aluminum piping of the boom. As a result the
collar had to be positioned carefully on the stanchion and tightened hard to prevent it
from turning. Despite the problems, the booms performed well through the seven days
of testing.
The second generation of water jet boorns were made from 3 m sections of 7.6
cm ID standard aluminum pipe with three 0.6^ cm x 3.8 cm aluminum strips welded
symmetrically (120° spacing) down the length of the pipe (Figure 27). Standard weld
61
-------
"ABLE 7. WATER 3ET/O1L SKIMMER FEASIBILITY TEST MATRIX
Test
no.
SD-1
SD-2
1
2
3
4
5
6
T
&
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Tow
speed
(kts)
0-4
0-6
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
' 4
2
4
6
Wave
Calm
Calm
Calm
Calm
Calm
Cairn
Calm
Calm
Cairn
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Slick
thk
(mm)
0
0
2
2
2
2
2
2
z
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Slick
width
Cm)
0
0
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
4.25
6
6
6
Nozzle
ID
(cm*
—
—
2.1
2.1
2.1
2.7
2.7
2.7
1.5S
1.58
1.58
1.58
1.05
1.05
1.05
1.05
1.05
1.05
1.58
1.58
1.58
1.58
2.1
2.1
2.1
2.7
2.7
2.7
2.7
2.7
2.7
2.1
2.1
2.1
2.1
2.1
2.1
No. of
nozzles*
0
0
0
1
1
1
1
I
1
1
i
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
3
3
Pressure
(kPa)
0
0
0
210
420
560
210
H20
550
210
420
560
690
210
420
690
210
420
690
210
280
420
690
210
420
560
420
420
560
210
420
560
210
420
560
210
210
210
Nozzle
angle
in/iwd
(deg)
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
n / n
v W
0/0
0/0
0/0
0/0
0/0
0/0
0/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
10/0
20/0
20/0
20/0
20/0
20/0
20/0
0/0
0/0
0/0
Length
of
boom
(m)
—
7
7
7
7
7
7
•7
"7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
Continued
62
-------
"ABLE 7. (Continued)
Test
no.
37
3£
•a a
40
ill
U2
143
ij L
145
46
47
48
H3
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
Tow
speed
(kts)
14
14
f:
4
14
<4
4
b
l±
4
it
14
4
14
14
14
4
14
14
It
4
14
t4
14
6
6
14
4
6
6
14
14
6
6
2
14
6
Wave
Cairn
Cairr.
Calm
Calm
Calm
Cairn
Calm
CaJm
Cairr
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
Calm
0.5m
0.5m
0.5m
Slick
thk
(mm)
2
2
*~t
_/
2
2
2
2
2
*/
2
2
2
2
2
2
2
2
2
2
2
TBD
TBD
2
2
2
2
2
2
2
2
2
2
2
2
HC
HC
HC
Slick
width
Cm)
6
6
6
6
6
6
6
6
t
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
2
2
2
Nozzle
ID
(cm)
2.1
1.58
1.58
1.5&
1.58
2.1
2.1
") "7
•L, « ^
2.7
2.7
2.7
2.1
2.1
2.1
2.1
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.1
2.1
2.1
2.1
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
6
6
6
No. of
nozzles*
3
3
_}
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
-1
1
1
2.7
2.7
2.7
Pressure
(kPa)
210
210
210
210
210
420
560
t20
560
420
560
*20
560
420
560
420
560
560
560
560
560
560
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
1
1
1
Nozzle
angle
in/fwd
(deg)
10/0
10/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
10/0
10/0
10/0
10/0
20/0
20/0
20/0
20/0
0/45
10/45
20/45
TBD
TBD
0/0
0/0
0/0
0/0
0/0
0/0
0/0
0/0
10/0
20/0
10/0
20/0
TBD
TBD
TBD
Length
of
boom
(m)
7
7
7
7
7
7
1
7
"7
7
7
7
7
7
7
7
7
7
7
7
7
7
12
12
12
12
12
12
12
12
63
-------
TABLES. u.S COAST GUARD SKIMMER/WATER 3ET TEST MATRIX (STATIONARY TEST)
CD
-C
Test
no.
1
2
3
4
5
6
7
8
9
10
ii
12
13
1*
15
16
17
18
19
20
21
22
23
24
Wave
(m)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.5HC
0.5HC
0.5HC
Q.5HC
0.3HC
0.3HC
0.3HC
0.3HC
Nozzle
ID No. of
(cm) nozzles
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 i
2.1 1
2.1 1
2.1 1
.2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
2.1 1
Water-
press.
(kPa)
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
Nozzle
tilt
angle
(de£)
0
22J4
it 5
0
0
22K
45
0
22ft
45
0
0
22ft
45
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Nozzle
Angle
fwd
(deg)
0
0
0
22 ft
45
22Ji
45
0
0
0
22Yi
4,5
22ft
4.5
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Slick
width
(m)
None
None
None
None
None
None
None
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Tow
speed
(kts)
0
0
0
0
0
0
0
4
4
4
4
4
4
4
6
6
4
4
6
6
4
4
6
6
Notes:
1.
2.
3.
Stationary tests had photos and movies taken through the underwater window.
Tow speed was simulated by swinging the water jet boom.
Oil slick was delivered on the water from a stationary bridge. Slick thickness was about 2 rnrn.
-------
TABLE 9. U.S. COAST GUARD SKIMMER/WATER JET TEST MATRIX (SLICK CONVERGENCE TESTS)
en
Test
no.
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Notes:
1.
2.
3.
Wave
(m)
0
0
0.5 HC
0.5 HC
0.5 HC
0.5 HC
0.5 HC
0.5 HC
0.5 HC
0.5 HC
0.5 x 15
0.5 x 15
0.5 x 15
0.5 x 15
0.5 x 15
0.5 x 15
Nozzle
ID
(cm)
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
• 2:1
2.1
No. of
nozzles
on one side
i
i
1
1
1
1
1
i
i
1
i
1
1
1
1
1
Water
press .
(kPa)
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
560
Nozzle
Tilt
angle
(deg)
TBD
TBD
0
0
0
• o
0
0
0
0
0
0
0
0
0
0
Nozzle
Angle
fwd.
TBD
TBD
0
0
45
45
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
Non-stationary testing.
Slick length 45 m.
Oil slick thickness 2 mm.
Slick
width
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
Tow
speed
Length
of boom
4
6
4
6
4
6
4
6
4
6
14
6
4
6
LI.
6
20
20
20
20
20
20
9
9
12
12
12
12
9
9
20
20
-------
flanges were welded at each end of the pipe sections. These allowed the sections to be
joined and separated easily. With a rubber gasket between the flanges very little
water leaked even at a pressure of 700 kPa. The construction proved to be
lightweight, easy to handle, capable of holding the water pressure, and stiff enough for
easy rigging and consistent performance in waves. This design was used for the
stationary boom pivoting tests, some tow tests on the catamaran, and then was stored
to be used on the U.S. Coast Guard's ZRV skimmer when it came to OHMSETT for
testing.
DISCUSSION OF RESULTS
The results obtained from earlier tests were again proven by these series of
tests (Table 10)—the larger the nozzle and 'the greater the pressure, the better the
performance. Comparison of the plots of slick movement using water jets from 1.25
to 2.66 cm ID bear this out clearly.
The benefit of angling the jets was also established in these tests. By angling
the jet in the direction of the desired oil movement performance was increased on 7 rn
booms. Even an angle of ten degrees was beneficial (Figures 32 through 3k). The tests
only included inwardly directed angles up to 20 . The reason for the increased
performance in the use of the horizontal component of force of the angled water
stream to push the oil. The reduction of the amount of air entrained deeply by not
having the jet vertical did not have an effect on these tests since the objective was to
move the oil quickly—not to hold the oil in place after it had been moved. Using a 7 m
boom (including nozzle fittings and swivel joints at the vertical stanchion) on the
catamaran the slick had to be converged in 3.6 seconds at four knots. The slick
holding potential of the water jets was not required for such a short interaction
interval. The slick was moved further using a 12-m boom and the angling of the jets
inward did not seem to consistently increase performance (Figures 35 and 36).
The forward angle of the water jets was not beneficial to performance (Figures
37 and 38). The theory behind the forward angle was to place the point of impact
further ahead of the skimmer, essentially increasing the length of the boom. The use
of a longer boom increased performance (Figures 35 and 36) but the water jet nozzle
needs to be relatively close (approximately 1 m) to the point of impact to perform
well. By angling the jet forward the travel path of the water stream was increased
beyond the distance where the stream began to lose coherence. Penetration and air
entrainment was reduced and the impact area of the water was increased. The
horizontal force component of the water stream was directed forward, which did not
help to converge the slick. At times the forward angled jet did produce a dramatic
initial wave which rolled the oil away from the jet. It appeared to "plow" the surface
of the water over and give the oil a push off to the side. The plowing effect was
especially noticeable when the jet was angled forward and inward (Figure 39).
However, this initial push was not enough to make up for the loss in current usually
developed by the entrained air and the set of rolling, breaking waves which a vertically
directed jet produced (Figures 35 and 36).
The pitch of the catamaran in waves resulted in the worst performance by the
angled water jets. Vessel roll and heave also caused changes in impact point and
length of travel of the water jets but the effects were not as dramatic as those caused
by pitch (Figure 40). Because the jets were extended over 6 m beyond the bows of the
66
-------
TABLE 10. WATER 3ETS TEST RESULTS (SLICK CONVERGENCE TlISI'S).
en
-j
Boom
igt
(m)
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
Nozzle
I.D.
(cm)
1.25
1.25
1.25
1.25
1.25
1.25
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
Tow
speed
(kts)
it
4
it
4
^
it
14
It
It
It
tt
it
4
ft
it '
it
it
6
2
-------
TABLE 10. (Continued)
01
CO
Boom
Igt
(m)
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
12
Nozzle
I.D.
(cm)
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
2.1
Tow
speed
(kts)
14
4
14
4
4
4
4
4
4
4
4
4
4
4 -
4
4
6
6
6
6
6
6
6
6
6
4
Press.
(kPa)
560
560
560
560
560
590
590
590
590
590
590
590
590
590
590
590
210
590
590
590
590
590
590
590
590
590
Nozzle
Angle
in/fwd
(deg)
10/0
10/0
10/0
20/0
20/0
10/0
10/0
10/0
0/45
0/45
10/45
20/45
20/45
20/45
45/45
45/45
0/0
0/45
10/45
10/45
20/45
20/45
20/45
20/45
45/45
0/0
Slick
thk
(mm)
2.2
2.1
2.1
2.1
2.1
1.6
2.1
3.0
2.1
2.1
2.1
2.0
3.0
2.1
2.9
3.0
3.1
2.0
3.1
3.1
3.1
2.9
2.9
2.1
2.9
2.1
No. of
nozzles
on one side
1
1
i
1
1
1
1
i
1
1
1
1
1
1
1
1
3
1
1
1
1
I
A
1
1
i
1
Slick
move
(m)
2.97
2.89
2 . 89
3 . 20
3,04
2.59
2,7't
2. 13
2,43
2.59
3.65
2.74
2 . it 3
2.7H
2.28
ind
7.13
i.A7
2Jl 3
1 .(,7
\ .52
2 . I 3
2.59
Ind
2. 13
3.12
Wave
(m)
C
c
C
c
c
c
c
c
c
c
'C
0.5 HC
0.5 HC
C
C
0.5 HC
C
C
c
c
c
c
0.5 HC
0.5 HC
C
C
Orig
width
(in)
4 . 26
<4 , 26
4 . 26
4 . 26
4.26
6.08
6.08
6.08
4.26
6.08
6.08
4.26
6.08
4 . 26
4.26
4 . 26
6.08
4.26
4.26
4.57
4.57
4.26
4.26
20
4.26
20
Final
width
(m)
1.29
4.41
4.41
1.06
1.21
3.50
3.35
3.96
1.82
3.50
2.43
1.52
3.65
1.52
1.98
Ind
3.96
2.89
1.82
2.89
3.04
2. 13
1.82
Ind
2.13
2.97
Test
no.
24
35
32
31
36
42
<*J
w
71
70
5-7
78
67
76
SO
82
39
72
5-8
S-9
5-10
77
79
66
81
49
(Continued)
-------
TABLE 10. (Continued)
Boom
Igt
(m)
12
7
7
7
7
7
7
7
7
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
6
6
6
6
6
9
Nozzle
I.D.
(cm)
2.1
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.1
2.1
2.1
2.1
2.1
2.1
Tow
speed
(kts)
6
it.
4
4
it
4
it
t
6
2
4
it
4 .
it
'4
It
It
6
6
6
6
6
6
6
*
4
4
4
6
it
Press.
(kPa)
590
210
245
245
t2Q
420
420
490
490
180
180
180
• 180
180
490
490
490
180
180
180
180
490
490
490
590
590
590
590
590
590
Nozzle
Angle
in/fwd
(deg)
0/0
0/0
10/0
20/0
0/0
10/0
20/0
20/0
20/0
20/0
0/0
10/0
20/0
20/0
0/0
10/0
20/0
0/0
10/0
20/0
20/0
0/0
10/0
20/0
0/45
0/45
45/45
0.45
45/45
0/45
Slick
thk
(mm)
3.1
2.9
1.1
2.2
2.2
1.1
1.1
2.1
2.1
2.2
2.3
2.1
2.0
2.1
2.1
2.1
2.1
3.1
3.1
3.0
2.1
4.6
3.1
3.1
2.1
2.3
2.4
2.4
2.2
2.0
No. of
nozzles
on one side
1
1
i
1
1
1
1
1
1
1
1
i
I
1
i
i
i
1
i
1
1
1
1
i
i
i
i
i
i
i
i
Slick
move
(m)
2.43
J.67
2 . 1 3
I.R2
2.13
2.66
2.59
Ind
2.13
Ind
2.89
3.20
3.15
Ind
3.81
3.81
3 . 50
2.43
2.28
3.04
1.82
2 . 4 3
2. 59
2.X 9
2.7/*
1.82
2.28
2.13
2.43
2.28
Wave
(m)
C
C
C
C
C
C
C
C
C
0.5 Hi:
C
C
C
0.5 HC
C
C
C
C
C
C
0.5 HC
C
C
C
0.3 HC
0.6 HC
C
0.3 HC
C
C
Orig
width
(rn)
6.08
4 . 26
4 . 26
4.26
4 . 26
4 . 26
4 . 26
6.08
6.08
6. OS
6.08
6.08
6 . 08
6.08
6.08
6 . 08
6.08
6.08
6.08
6.08
6.08
6.08
6.08
6.08
4.57
4.57
4.57
4.57
4.57
4.57
Final
width
(m)
3.65
2.59
2.13
2.43
2.13
1.60
1.67
Ind
3.95
Ind
3.20
2.89
2.74
Ind
2.28
2.28
2.59
3.65
3.81
3.04
4 . 26
3,65
3.50
3 . 20
1.82
2.74
2.28
2.43
2.13
2.28
Test
no.
50
9
28
30
8
27
29
68
69
63
57
59
61
64
56
55
54
58
60
62
65
5J
52
53
18
i 7
15
19
16
20
-------
C4.5
K
M
0
5
M
E 3
N
N
M
E
T
E
R
S
2.5
2
.5
u
I-
OR1ENTATION OF WAI ER JET i!07.ZLE
h- 8/0 (ANGLE IN/ANGLE FWiV)
D- 18/8 (ANGLE IN/ANGLE ruf»
0
100
200
300 400 580
WATER JET PRESSURE (KPa>
808
708
Figure 32. Performance of a 1.25-cm ID water jet at H kt in calm water (oil slick convergence test)
2.2-mm slick.
-------
' >•- -"•>,'•" ' ,' • /r.~" fvii.•«*•"•• ,<
ii'A :>••••".' ' '•.-£&$r * .
^\-->^v\1iJi^'''-^>^
; .; ' -, i • , .'tfi^Stf ~ \. *
Figure 33. An inwardly directed nozzle on a single water jet boom mounted ,
on the OHMSETT catamaran. Note that the greatest portion of current energy
is directed in towards the centerline of the system.
71
-------
S I
L 5 i
I I
C4.5 j-
K
M "
0
ORIENTATION OF WATER JET NOZZLE
A- 0/0 CANGLE IN/ANGLE FWD) -1 KTS
D- 10/0 CANSLE IN/ANGLE FWD) 4 KTS
0- 0/0 CANGLE IN/ANGLE FWD) >\ KTS, 3
JETS
0/0 CAN8LE IN/ANGLE FWD) 6 KTS, 3 JETS
M
E
N
J.
H
T
E
R
S
r
2
u
0.5
0
200
300 400 500
WATER JET PRESSURE (KPa)
880
780
Figure 34. Performance of a 1.6-cm ID water jet at 4 kt and 6 kt operating in cairn water (oil slick
convergence test) 2 to 3-mm slick.
-------
-•J
lA)
r
s
L b
1
C4.5 I-
0
E3'5
M
E 3
N
T2.5
I
N 2
!_
L
3 JETS, 2 KNOTS
A
ORIENTATION OF WATER JET NOZZLE
A- 8/0 CANSLE IN/ANGLE FWD.)
0- 10/8 (ANGLE IN/ANGLE FW[»
0- 28/0 CANGLE IN/ANGLE FWD)
i~ 0/45 CANGLE IN/ANGLE FWD)
0- 28/45 CANGLE IN/ANGLE FWD)
•- 45/45 CANGLE IN/ANGLE FWD)
O
•r:.i
•A
A 12 METER BOOH
1C TEST
T
E
R
S
0.5
280
608
700
388 488 580
WATER JET PRESSURE CKPa>
Figure 35. Performance of a 2.1-cm ID water jet at 4 kt. Oil slick of 2-3-mm thickness, calm water,
7-m boom (oil slick convergence test). Note: A harbor chop test at U kt, a calm water test at 2 kt,
12-m boom test, and a test using three jets were plotted for comparison.
-------
s
L
I
C
K
M
0
V
E
M
E
N
T
I
N
M
E
T
E
R
S
5
4.5
4
3.5
3
2.5
2
1 .5
!
8.5 *-
0
88
ORIENTATION OF WATER JET NOZZLE
A- 0/0 CANGLE IN/ANGLE FWD)
D- 0/45 CANGLE IN/ANGLE FWD)
0- 10/45 CANGLE IN/ANGLE FWD?
i- 20/45 CANGLE IN/ANGLE FWD)
0- 45/45 CANGLE IN/ANGLE FWD3
o
12 METER BOOM'
•1C TEST
A 3 JETS
O
n
200
300 400 500
WATER JET PRESSURE CKPcO
608
700
Figure 36. Performance of a 2.1-cm ID water jet at 6 kt operating on a 7-m boom in calm water (oil
siick convergence test). Note: A harbor chop test, a 12-m boom test and a multiple jet test were
plotted for comparison, all with 2-3-mm slick.
-------
I
C4.5
K
M «
0
N
M
3 *-
j
2.5 j-
ORIENTATION OF WATER JET NOZZLE
A- 8/8 CANSLE IN/ANGLE FWD)
D- 18/0 CANSLE IN/ANGLE FWD)
0- 20/0 CANGLE IN/ANGLE FWD)
0- —
D
\2 METER BOON,CALM UATFR
7 METER BOOM..CALM WATER
1.5h
-
0.5 h
0
\ 88
288
380 488 588
WATER JET PRESSURE CKPa>
_i__~
600
700
Figure 37. Performance of a 2. 7-cm ID water jet at 4 kt on a 7-m and 12 m boom foil slick convergence
test), 2.3-m slick.
-------
s
[
L
C4.5 h
K
M
0
V
H
E
N
T
I
N
M
E
T
E
R
S
4 h
3 (-
2.5 -
2
\.5\-
0,5
8
I
80
ORIENTATION OF WATER JET NOZZLE
A- 0/8 CANGLE IN/ANGLE FWDD
D- 10/0 CANGLE IN/ANGLE FWD)
0- 28/8 CANGLE IN/ANGLE HUD)
4 KNOT TESTS,CALM WATER
6 KNOT TESTS,CALM WATER
<>6 KNOT TEST, HARBOR CHOP
280
308 400 508
WATER JET PRESSURE CKPa)
688
700
Figure 38. Performance of a 2.7-cm ID water jet at 4 kt and 6 kt operating on a 12-m boom (oil
slick convergence test) .
-------
—^^^8
-»*,*•'»«: -"S*."! **.• >T
.' ***.
Figure 39. Water jet angled forward and inward during a clam water test.
(Note the rolling wave produced at the impact point).
77
-------
• £2 r
X"'
,-4,
':'- vr •••
.. • SL i'., ;•
}
*.
:%;^Sf|
^ <-<^J* - £L,"wB*1"
•%1& ..i:.
Figure 40. Water jet angled forward and inward during a wave test. (Note
the impact point traveling far forward and onto the ofl slfck due to the rear
pitch of the catamaran).
78
-------
nulls, the amplitude ol piich was increased at the water jet nozzles. When the nozzles
were raised upward during a stern pitch of the catamaran the point of impact moved
dramatically forward from its calm water or Intended position. When the jet was
angled at 45 Inward and 45° forward, the water sprayed over the oil slick entraining
oil and caused an irregularly-shaped slick. This also lengthened the path of travel of
the water stream and thus decreased the effectiveness of the jet. When a bow pitch
was experienced the impact point was brought back across the slick to directly
beneath the nozzles. During some wave tests the performance of the water jet was
indetenninant because the resulting slick was so irregular.
-o
One of the most important finds of this test program was that angling the water
s not beneficial when operating in wave c
I, and heave. Since such conditions are the norm in oil spill recovery a
general operation rule can be made—point the jets straight down into the water. This
simplifies the construction and use of the water jets. Those of us in the relatively
pristine world of test tanks are prone to strive for the optimum angle and operating
pressures to tweak the 'ast bit of r.>erforrnance from the system. Those neopie who
work in the usually oil-bisckenc-c and uncomfortable field operation? are prone to use a
simple, dependable, and rugged deployment of a system. Their attention is often
called for in areas of personnel safety and labor-intensive duties. They have little
time to determine if the pitch of the skimmer has changed sufficiently over the last 15
minutes to warrant a change in water jet impingement angle. A system which has the
best chances of performing well when used in its simpliest configuration will probably
be looked upon favorably by field operators.
Three water jets in tandern, spaced about 1 m apart, performed as well as or
better than one water jet at the same pressure (Figures 34 and 35). But by using more
than one jet, a significant drop in available water jet pressure was experienced. In
some instances an increase in pressure of one water jet could equal the performance of
the three jets with reduced pressure. A possible drawback to using the tandem
arrangement at high tow speed was that the wave train produced by the three jets
persisted longer than that produced by a single jet (Figure 41). Although the breaking
waves move oil, they also entrain it slightly below the surface. The entrained oil may
not have sufficient time to rise if the breaking wave persists into the mouth of the
skimmer.
The tests conducted with the catamaran stationary and pivoting the water jet
boom in an arc provided an interesting view of oil slick movement mechanisms and
entrainment characteristics of a water jet. From the underwater window the point of
view of a particle behind and beneath a water jet was available. The vertically
directed jets appeared to entrain the most "air and to a greater depth, which
maintained the surface current caused by the rising air bubbles for the longest period
of' time. The angled jet moved the oil the fastest but also entrained the most oil.
79
-------
f ''"'^V' v."* > t; :1 ''-V •'*. v.':1!-- . ,'T|C!" '•"
Figure 41. Tandem water jets during a tow test. (Note the bow wave of
the second water jet coincided with the second wave of the first jet).
80
-------
SECTION
WAT
INTRODUCTION
Water jets on Individual floats have the potential to solve many problems
associated with oil spill recovery operations. Equipment deployment, wave effects,
ship traffic Interference, and fire are some of the hindrances which could be coped
bv proper use of water iets on floats.
Equipment deployment—an oil barge offloading site is often required to ring the
barge with a fabric boom before oil can be offloaded. Obviously the boom cannot be in
place before the barge arrives and therefore a trained boom deployment/retrieval
team must be employed after the barge arrives and before it leaves. A water jet
system could be used In place of a fabric boom. Water jets on floats could be supplied
by submerged hoses, can be left in position, and the only action required would be to
start a purnp and turn a valve or two. The water jet floats could be bumped aside or
even momentarily submerged by the barge and tug as they arrive or leave.
Wave effects—when using conventional fabric booms to converge an oil slick
into a skimmer the reflection of small waves between the booms cause problems. The
waves are finally concentrated in front of the skimmer inlet causing oil entrainrnent,
oil loss from the booms, and a decrease in skimmer performance. A series of water jet
floats used in place of the booms (Figure 42) could allow waves to pass and yet
converge the oil.
Ship traffic interference—if an oil spill occured and oil retaining had to be
conducted in a ship channel the damage caused by a wayward vessel could be
minimized if it passed into the retained oil slick through a water jet float line. Many a
fabric boom busy retaining oil has been destroyed by errant ship traffic. The result is
a loss of oil retention until the vessel is removed and the boom repaired.
Fire—the possibility of damage to water jet floats by a fire is less than to a
conventional fabric boom since the floats and jets can be made from steel. Since the
action of the water jets maintain the oil away from the equipment, the flames may not
even reach the water jet floats to endanger them.
Possibilities such as these prompted a series of tests to be conducted at
OHMSETT which would determine the feasibility of using water jets on Individual
floats to control an oil slick. The tests were aimed at the use of such floats in a fast
current situation. This chapter presents the results of those tests.
81
-------
1.2 x 2.^-m plywood
CD
NJ
/ Water let noszle
Water supply hose
and tow line
Inflatable bags tied to the
plywood.
Figure 42. Isometric drawing of a water jet float.
-------
CONCLUSION'S
The use of water jets mounted on individual floats to control an oil slick is
feasible. However, there are problems which must be solved before the concept
becomes practical for field use.
The construction of water jet floats can be done using plywood, standard pip' r
material, and suitable floatation (e.g., inflatable bags, steel drums, logs).
Water jet floats allow waves normally reflected by converv: -.al fabric booms
to pass whije retaining an oi! slick. ^*
Maintaining the individual floats in a predesigned orientation and formation
while towing proved difficult. Floats drifted behind one another due to the fluid drag.
Before proper counterweights were used to counter the forward pitching force of the
supply hose, the floats would occasionally submerge at their bow and flip over.
RECOMMENDATIONS
Since only one side of a converging boom system was tested the performance of
a complete oil slick converging system can only be extrapolated. Another test series
should be conducted using at least three floats per side. The proper orientation and
relative position of the floats should be easier to maintain because tie lines could be
used across the sweep width. They would serve to stabilize each float by using its
mirror image to supply a corrective force to balance the drag forces on the floats.
Three prototype permanent water jet floats could be built and placed in the
OHMSETT tank behind the wave generator. They would serve to keep oil from gaining
entrance behind the flaps and becoming emulsified. The floats would also show the
possible problems which could develop with the water jet floats when used in a rough
environment.
A water jet float more suitable for towing in a desired pattern with other floats
should be designed and tested. Perhaps a circular float such as a tire inner tube would
be advantageous since a slight rotation of the system would not cause a change in the
resultant drag forces. A rudder skeg on the underside of the type of floats used in
these tests should also be investigated.
TEST DESCRIPTION
Test Equipment
The water jet floats (Figure ^2) were constructed from inflatable fabric bags
lashed by rope to a 1.2 x 2.4 m piece of plywood 1.3 cm thick. A base and brace was
bolted to the top of the plywood to support the 2.5 cm ID piping. A reducing elbow
was mounted beneath the plywood and inbetween the floats to connect the 7.6 cm
water supply hose to the steel piping. A 30 cm long, 2.1 cm ID pipe was used as the
nozzle. The nozzle exit was directed vertically downward and set at a mean height of
0.6 m from the water's surface. The 7.6 cm ID flexible water supply hoses doubled as
tow cables for the floats. The floats were held in their relative positions by 1 cm rope
tied to the auxiliary, video, and main bridges (Figure ty3 and tyty). Pressure gauges were
83
-------
Direction of tow
IT:-.
J i J1.
I;
JL .^.
Wain
Main
Bridge
2 Water supply hoses..
1 Test engineer
2 Test director
3 Oil distributor
U Water pump operator
5 Photographer
6 Control room operator*
7 VDU operator*
8 Filter operator*
*Not shown
\
Water
Jet
Floats
Figure 43. Test set up for water jet float program.
-------
Figure 44. Water jet floats under tow diverting an oil slick.
-------
installed in the water supply lines on the main bridge In advance of the 7.6 crn nose
connections. To prevent the floats from nosing down in front due to the weight and
drag force of the 7.6 cm supply hose, weights were placed on the floats and over the
rear to counter the hose forces.
Towards the end of the test program, an independent water jet fjoat was built.
A high pressure (420 kPa) gasoline engine water pump was mounted on a small
OHMSETT catamaran work boat (Figure 45) and towed from the main bridge via a 1.3
crn rope.
The slanting pattern of floats across the tank was designed to divert the oil
slick across the tank in incremental steps. The floats were separated by 15 m down
the tank and L8 m across the tank. Oil was distributed from the main bridge in a slick
initially 4.5 m wide and 3 mm thick.
Test Plan
A test matrix was designed for these tests (TabJe 11) in conjunction with the
U.S. EPA to investigate the effects that tow speed and waves nave upon water jet
float performance. Due to the nature of prototype testing, not all of the proposed
tests could be conducted.
All tests were conducted according to the test plan presented below in order
that the tests could be compared to one another.
Test Procedures
1. The water jet floats were positioned in the test tank.
2. The proper test number was placed in the display board.
3. Oil distribution was set to deliver the desired slick thickness for the tow
speed.
4. If the test was to involve a harbor chop wave, the wave generator was
started and the waves allowed to build up for 10 minutes.
5. The photo/video department took their positions.
6. Water to the water jet floats was turned on and the desired pressure
obtained.
7. The oil skimming booms beneath the auxiliary bridge and main bridge
were raised.
8. The tow was begun by bringing the bridges up to the designated tow
speed.
9. Oil distribution was started and continued for two hundred feet of tow.
86
-------
c
"
*>/*\xf?V:%il?r|:4i;J11
1
Figure 45. Water jet workboat with gasoline pump.
87
-------
TABLE 11. WATER 3ET FU
TEST MATRIX
Test
no.
1
2
3
i
H
sr
6
7
8
9
10
11
12
13
1*
15
16
17
18
19
20
21
22
23
2*
25
26
27
28
29
30
31
32
Tow
speed
(kts)
0-4
4-6
2
t
6
2
4
6
2
^T
b
2
4
6
2
4
6
2
-------
10. After oil distribution \\ as corr.'plcted the bridges were slowed to a halt
and the skimming booms Jc\vered.
11. If a harbor chop wave was used during trie-test, time was allowed for the
waves to sufficiently subside to alJow for oil skimming by the bridge
booms.
12. The bridges were returned to the north end of the towing tank at 0.5 kts.
The oil on the surface was thus cleared so not to interfere with the next
test.
Results of the tests were recorded by still and movie photography and on video
tape.
DISCUSSION OF RESULTS
Tne water jet fioat concept performed well but problems with T.ainiaining fjoat
position and stability in a diversionary mode of operation must be solved before the
floats can be considered a viable alternative to fabric booms. An advantage to the
water jet float system over the fabric boom is the ease of relocating a poorly
positioned fioat to divert oil rather than realigning an entire boom section while
fighting the current. The floats in the tests were positioned 15 m apart measuring in
the longitudinal axis of the tank and 1.8 m in the transverse axis. These positions were
selected for tests using tow speeds of from 4 to 6 kts. The spacing seemed to work
well for the ^ kts tests but fell a little short for the 6 kts tests. The oil slick was not
diverted the entire 1.8 m before the following float contacted the oil slick. However,
for 2 kt tests it appeared that the transverse spacing could have been increased to
about 3 m. To move a water jet over 1.2 meters would require little effort if the float
was positioned by a bridle to two anchor points upstream and on either side of it. The
draft of the floats was about 5 cm with a projected cross current length of 0.5 m. This
resulted in a projected area of about 0.025 m^. A fabric boom with a draft of 0.5 m
and a projected length of 3 m would have a final projected area of 1.5 m*. The force
required to overcome the fluid drag on the boom would be 60 times that to move the
water jet float. Using FzpAv^Cf} as the equation for drag force and letting Cj} = 1.5.
The force to move the fabric boom in a current of 2 knots would be about 118 kg.
While the force required to move the water jet float would be about 2 kg. Problems
with ropes stretching and breaking, knots giving way or anchors moving would be
greatly reduced using water jet floats.
The structure of the water jet floats used in the test program was dictated by
the materials on hand or readily available. The problems of front end submergence,
capsizing, and position drift could be solved by proper float design and water supply
hose location. The small work boat which had the gasoline driven pump onboard
experienced no stability problems. Proper rigging or the use of a rudder skeg could
eliminate any position drift problem. If two sets of water jet floats are used in front
of a skimmer (Figure 46), the tie lines and drag force of the skimmer should be able to
keep the floats in position.
The water jet floats performed as well in harbor chop waves as in calm water.
The vertically directed jets maintained their approximate point of impact despite the
roll, pitch, and heave of the buoyant floats.
89
-------
Direction of Tow
I Main
1 Bridge
Water
supply
hose/tow
ine
Oil Skimmer with
water jet booms
Figure 46. Double-sided water jet boom used in conjunction with a skimmer.
90
-------
The use of a high pressure gasoline-engine pump to power a water jet instead of
using a hose from the bridge pump seemed to have more advantages than disadvan-
tages during the tank tests. During field operations logistic problems may outweigh
those advantages. The need for the heavy water supply hose was eliminated with an
individual pump on the float. Towing and maintaining float position and stability was
made easier. In the field there would be no hose to be deployed, rammed, ruptured, or
Jos*. The drawback is the maintenance of the pump so that it performs continuously.
A large gasoline supply can be included on the float, but it must be refilled eventually.
The pump inlet may become clogged by debris or the machinery may break down, thus
leaving a breach in the oil spreading defenses. However, a more reliable electric-
driven pump mounted on shore or a large vessel would necessitate using the supply
hose.
91
-------
REFERENCES
i. Roberts, A.C. Using Fire Streams with a Self-propelled Oil Spill Skimmer.
EPA-R2-113, U.S. Environmental Protection Agency, Cincinnati. Ohio, 1973.
2. Katz. Bernard anc- R. Cross. Use ol Fire Streams to Control Floating Oil, EPA-
R2-73-113, U.S. Environmental Protection Agency, Cincinnati, Ohio, 1973.
3. Graham, D.J., R.W. Urban, M.K. Breslin, and M.G. Johnson. OHMSETT
Evaluation Tests; Three Oil Skirn'Tiers anc' a Water jet Herder, EPA-SOO/2-SO-
020. U.S. Environmental Protection Agency, Cincinnati, Ohio, 198C.
4. Breslin, M.K. Performance Tests of High Speed ZRV Oil Skimmer, U.S.
Department of Transportation, U.S. Coast Guard, Office of Research and
Development, Report No. DOT-CG-842702-A, Washington, D.C., 1980.
5. Hires, R.I., D.T. Valentine and 3.P. Breslin. Literature Search on Plunging
Water 3ets for Oil Spill Containment, 3uly 1979, unpublished report.
6, Valentine D.T. and R.I. Hires. Theoretical Analysis to Predict the Performance
of a Penetrating Water 3et in Controlling Oil Spills, 3uly 1979, unpublished
report.
7. . Breslin, 3.P. Flow Pattern Induced by a Vertical Translating Water 3et
Penetrating the Water Surface, 3uly 1979, unpublished report.
92
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APPENDIX A
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
:•'">-", '-> J'~ T -n'frf, f "^.""^'-i:
i^s-J.^.^ * ">;;**, 4 P1-^
The U.S. Environmental Protection Agency operates the Oil and Hazardous
Materials Simulated Environmental Test Tank (OHMSETT) located in Leonardo, New
Jersey. This facility provides an environmentally safe place to conduct testing and
development of devices and techniques for the" control and clean-up of oil and
hazardous material spills.
The primary feature of the facility is a pile-supported, concrete tank with a
water surface 203 meters long by 20 meters wide and with a water depth of 2.4
meters. The tank can be filled with fresh or salt water. The tank is spanned by a
bridge capable of exerting a horizontal force up to 151 kilonewtor.s while towing
floating equipment at speeds to 3.3 meters/second (6.5 knots) for at least ^0 seconds.
Slower speeds yield longer test runs. The towing bridge is equipped to lay oil or
hazardous materials on the surface of the water several meters ahead of the device
being tested, so that reproducible thicknesses and widths of the test slicks can be
achieved with minimum interference by wind.
93
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a
The principal systems of the :ank include a wave generator, a beach, and
filter system. The wave generator and absorber beach can produce regular waves to
0.6 rneter high and to 45 meters long, as well as a series of 0.7 meters high reflecting,
complex' waves meant to simulate the water surface of a harbor. The tank water is
clarified by recirculation through a 410 cubic meter/hour diatomaceous earth filter
system to permit full use of a sophisticated underwater photography and video imagery
system and to remove the hydrocarbons that enter the tank water as a result of
testing. The towing bridge has a built-in oil barrier which is used to skim oil to the
North end of the tank for cleanup and recycling.
When the tank must be emptied for maintenance purposes, the entire water
volume of 9800 cubic meters is filtered and treated until it meets all applicable State
and Federal water quality standards before being discharged. Additional specialized
treatment may be used whenever hazardous materials are used for tests.
Testing at the facility is served from a 650 square meters building adjacent to
the tank. This building houses offices, a quality control laboratory (which is very
important since test fluids and tank water are both recycled), a small machine shop,
and an equipment preparation area.
This government-owned, contractor-operated facility is available for testing
purposes on a cost-reimbursable basis. The operating contractor, Mason & Hanger-
Silas Mason Co., Inc., provides a permanent staff of eighteen multi-disciplinary
personnel. The U.S. Environmental Protection Agency provides expertise in the area
of spill control technology and overall project direction.
For additional information, contact: Richard A. Griffiths, OHMSETT Project Officer,
U.S. Environmental Protection Agency, Research and Development, MERL, Edison,
New 3ersey 08837. Telephone: 201-321-6629.
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APPENDIX B
OHMSETT OIL PROPERTIES
OHMShTT test fluids (light, medium, and heavy oils) are sampled and analyzed
several times during the process of using them in testing. The steps and analyses are
detailed below. Some test programs do not involve all sample procedures and sampling
frequencies are many times different.
Test fluids in bridge storage tanks are sampled at least once daily. Some test
programs require more frequent sampling when test fluids are pumped onto the bridge
more than once a day. Samples are analyzed for the properties detailed in Table B-l.
TABLE B-l. OIL PROPERTIES
Sample
Prqgerty_
Viscosity
Surface
Tensions
Interfacial
Tension w/
Tank Water
Specific
Gravity
Temp
Method °C
ASTM D-88 Room
ASTM D-341 and
ASTM D-2161 75
ASTM D-971 Room
ASTM D-971 Room
ASTM D-287 Room
ASTM D-1298
Acceptable Ra:
Outpjjt
Vise. vs.
Temp Chart
dynes/cm
dynes/cm
Sp.Gr.
@60/60
Light
cSt
3-10
@25°C
24 to 34
@25°C
26 to 32
@25°C
0.83-0.91
Medium
cSt
100-300
@25°C
24 to 34
@25°C
26 to 32
(925°C
0.90-0.94
Qfi£
Heavy
cSt
500-2000
@25°C
24 to 34
@25°C
26 to 32
@250C
0.94-0.97
Bottom Solids ASTM D-96
and Water ASTM D-1796
Room % BS&W
less than 1%
95
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TECHNICAL REPORT DATA
[Plc'ase read Instructions on the reverse before completing)
\
4.
7.
9
12
15
REPORT NO. 2.
TITLE ANOSUBTITLE
The Use of Coherent Water Jets to Control Oil Soills
AUTHOR(S)
Michael K. Breslin
PERFORMING ORGANIZATION NAME AND ADDRESS
Mason & Hanger-Silas Mason Co., Inc.
P.O. Box 11?
Leonardo, NJ 07737
. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH H5268
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO
10. PROGRAM ELEMENT NO.
INE826
11. CONTRACT/GRANT NO.
68-03-26H2
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/1 If
. SUPPLEMENTARY NOTES
John S. Farlow, Project Officer (201-321-6631)
16. ABSTRACT
The ability of coherent water streams to induce a surface current in water and
thus control a floating oil slick was examined at the U.S. Environmental Protection
Agency's (USEPA) Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT)
The objective of the tests was to evaluate coherent water streams as an alternative to
fabric booms and water sprays in concentrating, diverting, and containing oil slicks.
The water Jets were constructed from standard pipe fittings and supplied with
water from common centrifugal water pumps. They were mounted on the main towing
bridge, built into small floats that were angled across the direction of tow, and
extended from the bows of a catamaran. Currents of up to six knots were induced by
towing the water jets from the main bridge.
The tests showed that coherent jets could induce a significant surface current
and move an oil slick with little oil entrainment. The non -breaking waves produced
by the OHMSETT wave generator did not greatly affect performance except where the jet
nozzels were cantilevered off the front of the catamaran. The best position for the
untended water jets tested was to be vertically directed at the surface of the water
with the outlet O.^f to 1.0 meters above the surface. The vertical component of a
coherent water stream was found to be as useful, if not more so, as the horizonal
component. A water jet supplied by a 30 kw electric motor/centrifugal pump system
oerformed better than a source of compressed air (210 kPA) extended 0.6 m below the
surface supplied by a 50 kw gasoline- driven air compressor.
17
a.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS b.lDENTlFIERS/OPEN ENDED TERMS
Performance Tests Spilled Oil Cleanup
Skimmers Protected Waters
Water Pollution Coastal Waters
Oil Oil Booms
13
DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report/
Rclca-c to Public Unclassified
nuj-oa^t- bu ruuxxu 20. SECURITY CLASS ^rw* page;
Unclassified
c. COSATI Field/Group
21. NO. OF PAGES
107
22. PRICE
EPA Form 2220-1 (9-73)
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