EPA-600/2-76-243
                                       November  1976
   WASTEWATER FLOW MEASUREMENT  IN SEWERS

             USING ULTRASOUND
                    by

              R. J. Anderson
            Sewerage Commission
             City of Milwaukee
        Milwaukee, Wisconsin  53201

                     and

                S. S. Bell
            W. H. Vander Heyden
               W. K. Genthe
            Badger Meter, Inc.
        Milwaukee, Wisconsin  53223
           Project No. 11024 FVQ
              Project Officer

           Clifford Risley, Jr.
   U.S. Environmental Protection Agency
                 Region V
         Chicago, Illinois  60606
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
    OFFICE OF RESEARCH AND DEVELOPMENT
   U.S. ENVIRONMENTAL PROTECTION AGENCY
          CINCINNATI, OHIO  45268

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                                 FOREWORD
 The 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  testimony  to the deterioration  of our natural
 environment.   The  complexity of  that environment and the interplay be-
 tween  its  components  require a concentrated and integrated  attack on the
 problem.

 Research and Development is  that necessary first step in problem solution
 and  it involves defining the problems, measuring its impact,  and search-
 ing  for solutions.  The Municipal Environmental Research Laboratory de-
 velops new and improved technology and systems  for the prevention, treat-
 ment, and management of wastewater and solid and hazardous waste pollutant
 discharges from municipal and community  sources, for the preservation and
 treatment of public drinking water supplies,  and to minimize the adverse
 economic, social,  health,  and aesthetic effects of pollution.   This publi-
 cation is one of the products of that research; a most vital communications
 link between the researcher and the user community.

As part of these activities,  the study described herein demonstrated and
evaluated a new technique  for measurement of  sewage  flow utilizing ultra-
sonic measurements  of stream depth and velocity.
                                    Francis T.  Mayo
                                    Director
                                    Municipal Environmental
                                    Research Laboratory
                                    111

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                               CONTENTS

                                                               Page
 Forward
                                                                111
 Abstract
                                                                 IV
 Figures
                                                                VII
 Acknowledgments
 Sections
 I      Conclusions                                               ,
 II     Recommendations                                           2
 III    Introduction                                              4
            Purpose and Scope                                     4
            Concepts                                              5
            Objectives                                             ^
            Theoretical  Approach                                   7
 IV     Installation                                            JQ
            Site Locations                                       TO
            Installation Details                                 25
 V       Operation &  Evaluation                                   36
            Design Modification                                  35
            General Analysis of Equipment Operation              40
            Cambridge Avenue                                     45
            South Shore Treatment Plant                          53
           College Avenue                                       58
VI     Discussion of Results                                    60
           Allowable Solids Loading & Air Entrainment           60
           Level Gauge Installation Criteria                    62
           Probe Foulling by Debris & Grease                    62
           Velocity Profiles & Probe Multiplicity               63
           Equipment Costs                                      64
                                v

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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 trade
names or commercial products constitute endorsement or recommendation for use.
                                     11

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                                FIGURES
 No.

  1     Ultrasonic Pulse Propagation Path Between
            Transceivers                                         0
                                                                 o

  2     Wave Shape of Ultrasonic Pulse                           8

  3     Block Diagram of Meter Electronics                      10

  4     Meter Installation in a Sewer for Measurement
            of Wastewater                                       ^Q

  5     Meter Electronics Unit                                  17

  6     City of Milwaukee Sewerage  System Map                    19

  7     Location and  Configuration  of the 60"
            Cambridge Avenue  Sewer                               20

  8     Head Diagram,  Vicinity of Cambridge Avenue
            Meter Installation                                  21

  9     Flow Record,  Cambridge Avenue Intercepter,
        September-October, 1975                                 22

        -a   Flow  Recording -  60" Cambridge Ave. Sewer           23

        -b   Level Recording -  54" Sewer Upstream of
               Cambridge Avenue Site                           24

10     Location of Meter Installation, South Shore             26

11     Profile of Sewers in the Proximity of South
           Shore Plant                                         27

12     Detail of Manhole and Sewer, College Avenue             28

13     400 kHz Ultrasonic Transceiver                          29

14     Multiple Probe Mounting Configuration                   29

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                                ABSTRACT

A new technique for measurement of sewage volume flow utilizing ultra-
sonic measurements of depth and velocity was demonstrated and evaluated.
The new technique, requiring no costly construction for installation, is
usable for open channel or partially full measurements.  The flow tech-
nique can accomplish measurement accuracies from 2 to 5% under conditions
of rapidly changing levels, surcharging, and back-up conditions.  Two
installations were accomplished on existing sewers in the Milwaukee Sewage
System, one 12h feet and the other 5 feet in diameter.  A continuous flow
record was displayed for each meter and performance of the meter instal-
lations was compared with magnetic flow meters at one site and head
velocity relations on the other site.  Relationship between average volume
flow, water level, and average velocity along selected horizontal chords
of the sewer cross section were determined.  The unit installed on the
5 foot diameter sewers operated for a period in excess of 18 months with-
out failure and has required only routine maintenance.  The flow technique
provides accurate measurement over a range of depths from 25% to full depth
in the sewer and from zero to the full flowing velocity of the fluid in the
sewer.  No deterioration of ultrasonic transducer probes has been detected
indicating their suitability for use in the sewer environment.

This report was submitted in fulfillment of Project No. 11024 FVQ by the
Milwaukee Sewerage Commission under the sponsorship of the U. S. Environ-
mental Protection Agency.  This report covers the period April 1, 1971 to
June 30, 1974, and work was completed as of September 30, 1975.
                                    IV

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                          FIGURES  (cont'd.)

 No.
                                                            Page

 34     Mag Meter Flow Readings During Transient Tests,
            South Shore                                         56

 35     Isovel Diagram, Circular Channel, 1/3 Full              70

 36     Isovel Diagram, Circular Channel, 2/3 Full              71

 37     Isovel Diagram, Circular Channel, Full                  72

 38     k-Factors,  Rectangular Channel                          73

 39     Kahl-Scientific Current Meter, Exploded View            74

 40     Vertical Velocity Profiles,  Jones Island
            Influent Channel                                    75

 41     Horizontal  Velocity Profile,  Jones Island
            Influent Channel                                    75

 42     k-Factor Versus Porportion of Depth                      77

 43     k-Factor Versus Liquid  Level                             77

 44     k-Factor Versus Liquid  Level  for  Various Probe
           Chord Levels                                         77

 45     Experimental Versus  Theoretical Velocity Data
           For  a Full  Circular Channel                         81
46     Circular Channel Geometry
                                                               82
47     Normalized Turbulent Velocities Versus
           Normalized Laminar Velocities, Full
           Circular Channel                                    83

48     Isovels for Turbulent Flow in a Partially
           Filled Pipe                                         85

49     Experimental Versus Theoretical Velocity Data
           For a Partially Filled Circular Channel             86

50     Normalized Turbulent Velocities Versus
           Normalized Laminar Velocities,  Partially
           Filled Circular Channel                             88
                               IX

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                         CONTENTS  (cont'd.)


                                                              Page

VII    References                                               55

VIII   Appendices                                               66

           Appendix A - Velocity Profile Analysis               67

               Experimental k-Factor Analysis                   67

               Computer Aided Theoretical Analysis              78

               Full Circular Channel Analysis                   80

               Open Circular Channel Analysis                   84
           Appendix B - Computer Program for Solution
               of the Navier-Stokes Equations for Laminar
               Flow in a Rectangular Open Channel               89
           Appendix C - Derivation Relating Laminar
               Chordal Velocity and the 6th Power of
               Turbulent Chordal Velocity                       93
           Appendix D - Summary of Ultrasonic Waste-
               water Metering Performance in Installation
               in Japan.                                         98
                                 vi

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                                 SECTION I

                                CONCLUSIONS

 1.    Ultrasonic velocity measurement equipment in conjunction with ultra-
      sonic level measurement equipment can be  utilized  for  the measure-
      ment of sewage volume  flow.
 2.    At a typical cost of $10,000  to $12,000 for  a height-velocity system
      (including probes,  indicator,  totalizer and  recorder), the equipment
      is sufficiently low in cost to achieve general use, can  be convenient-
      ly installed in new or existing sewers, requires a minimum maintenance,
      and  is  suited for long term operation  in  the sewer environment.
 3.    Installation of the  equipment  does not normally require  special
      constructions and/or metering  pits or  vaults.
 4.    Between 25%  of  channel  depth and  surcharged  conditions the corre-
      lation between  the average chordal velocity  and the average area
      velocity is  sufficiently predictable to enable the average chordal
      velocity level and area functions to be easily integrated electroni-
      cally providing flow information accurate to within approximately 2%.
 5.   Pulse leading edge detection in the ultrasonic velocity electronics
      is more susceptible to  fluctuations in solids loading and/or entrained
     air densities resulting in fluctuations in velocity measurement than
     is peak pulse detection.
6.   The velocity measurement portion has a 20  to  1 turn down  capability
     and with the velocity probes mounted at the 25%  level  the level measure-
     ment portion is limited to a 4 to 1 turn down.  This  gives the system
     an 80 to 1  turn down capability which well exceeded the flow ranges
     experienced.  System operation is limited  to  the  turbulent flow regime
     and flow media which do not contain large  quantities of entrained  air.

                                      1

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                        FIGURES  (cont'd.)

No.                                                           Part

15     Ultrasonic Probe Mounting Configuration,
           Cambridge Avenue                                    32

16     Ultrasonic Probe Mounting Configuration,
           College Avenue                                      33

17     Detailed Plan View, Ultrasonic Probe Mounting
           Configuration, College Avenue                       34

18     View Looking Upstream, Ultrasonic Probe
           Installation, College Avenue                        35

19     Basic Unit, Receiver-Transmitter                        37

20     Ultrasonic Pulse Packet                                 37

21     Timing Diagram                                          37

22     Modified Unit, Receiver-Transmitter                     39

23     ATC Performance Test                                    42

24     Received Signal, Clear Water                            47

25     Received Signal, Water With Entrained Air
           Bubbles                                             47

26     Received Signal, Clear Water, Expanded                  47

27     Received Signal, Clear Water, Further Expanded          48

28     Received Signal, Water with Entrained Air
           Bubbles,  Expanded                                   48

29     Flow and Velocity Output Signals,  Cambridge
           Avenue                                              49

30     Area Correction Factor - Circular  Pipe                  51

31     Measured Chordal Velocities Versus Depth,
           Cambridge Avenue                                    52

32     k-Factor Estimate,  Cambridge Avenue                     52

33     Measured Transient Flow Profiles,  South Shore           55
                               vin

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the foam surface absorbs the ultrasonic energy, precluding an echo.
The use of a load-length product to estimate the effects of entrained
solids loads in the transmission path length is advised, although most
applications appear to be well below recommended limits of 5,000 m-mg/Jl

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                              ACKNOWLEDGMENTS

The support and encouragement of Ray D. Leary, Chief Engineer and General
Manager of the Sewerage Commission of the City of Milwaukee is acknowledged
with sincere appreciation.

Design of the velocity probe mounting fixtures, and installation of the
ultrasonic metering equipment was performed by Kenneth Tappendorf of the
Milwaukee Sewerage Commission Staff.

Instrument design modifications, data collection and analysis, velocity
profile calculations and preparation of the final report draft were per-
formed by the Environmental and Electronic Products Group of Badger Meter,
Inc. of Milwaukee.  Also acknowledged are the valuable electronic design
efforts of Ray Thornborough, meter modifications and tests by Jack
Bradach, Al Nagy and Henry Horns, and the art work, plots and drawings of
Dennis Wachs and George Zunker, all of the Badger Meter staff.

The support and guidance of William Rosenkranz and Frank Condon of the
Waste Management Division and George Kirkpatrick formerly with the Division,
and of Project Officer Clifford Risley and Ronald Eng of Region V, U.S.
Environmental Protection Agency, are acknowledged with gratitude.  Also,
special thanks goes to Mr. Richard Field, Chief, Storm and Combined Sewer
Section, USEPA, for his suggestions and inputs, and thorough manuscript
review.

Also acknowledged are the helpful discussions held with K. Koyanagi,
M. Yamamoto,  and K. Tamura of the Tokyo Keiki Company,  Ltd.  of Tokyo,  Japan.
                                      x

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 backflows and surcharging.   Further,  in a sewage system regulated for
 minimization of raw sewage  discharge  into a watershed,  control practices
 involve sewer gating,  pumping and temporary retention in lesser used
 interceptors and trunks.  These practices generally alter the  character-
 istics of sewage flow  bringing about  unsteady flow,  high sewage levels
 accompanied by zero flow  in the conduits used for temporary storage,
 high and rapidly changing sewage levels,  and occasional surcharging  and
 backflow conditions.   Flow  properties of this sort render the  perform-
 ance of conventional open channel metering structures unsatisfactory and
 contribute to the need for  a sewer meter designed specifically for the
 application.

 With these points in mind,  two  metering sites were selected which were
 felt to be typical  in  that  both had downstream conditions which at times
 invalidated the  assumption  of  gravity flow.   Furthermore,  both sites  were
 partially filled,  circular  conduits one of which could  conceivably be
 subject to surcharging.

 CONCEPTS
 The  sewer flow measurement  technique  utilized in this demonstration was
 designed  to afford  accurate  flow measurement  while maintaining advantages
 of virtually  zero head loss, operation  under  submerged,  back flow, or
 surcharge conditions, and installation  conditions not requiring  signifi-
 cant construction.  Furthermore,  the  ultrasonic  sensors  are free  of
 significant intrusions and accordingly  are  not subject to  fouling,
 damage  by flow and  do not cause  flow  blockage.   The approach taken in-
 volved  a  new technique using integrated ultrasonic measurements of
 velocity  and level  and resulted  in a practical,  low cost  system  suited
 to wastewater characteristics and the operating  environment of the
 sewage  system.  The design of the equipment was  specifically adapted to
 the application, involves no moving parts, was shown to be suitably
rugged and non-fouling, and easily installed  in  existing  sewers with
manhole access.

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                               SECTION II
                            RECOMMENDATIONS

Operation of the flowmeters at their present locations should be con-
tinued for as long as possible to determine what, if anyf deterioration
of the probes might occur.

The effect of entrained air on transmission using probes having crystals
cut for higher frequencies should be investigated.

The method of using ultrasonic velocity and level measuring equipment
should also be developed to operate in relatively smaller line sizes of
6 to 36 inch diameters.  Unlike the ultrasonic sewage metering system,
present flume and weir devices have limited rangeability and are in-
operative under surcharge conditions.

Many sources within municipalities, consulting engineering firms and
state and federal pollution control agencies have identified the
need for reliable semi-portable sewage metering equipment particularly
for infiltration and loading studies in combined sewer networks.  Con-
sequently,  the development of a portable ultrasonic sewage flow monitor-
ing unit is desirable.

Until such time as the interference caused by entrained air is virtu-
ally,  if not completely,  eliminated, future installations of the ultra-
sonic sewage flow meter should be limited to those sites which do not
immediately follow either pumping or outfalls which contribute a sig-
nificant portion of the total volume at that site.  In addition, those
sites where agitation, outfall or pumping have caused the surface to be
foam covered are unsuitable for the level monitoring equipment in that

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       Reynolds Numbers for sewer channels of typical cross sectional
       configurations.  Determine the discharge coefficient associated
       with the above relationships and determine the universality of the
       discharge coefficient for typical cross section configurations.

 5.     Provide manual, computer, and automatic techniques for calculat-
       ing and displaying average sewage volume flow (rate and quantity).

 THEORETICAL APPROACH
 The general concept of the unique metering system was advanced earlier.
 In  the following,  the principle of operation of each major element of
 the system will  be explained.   These are the velocity meter,  height
 gauge  and the electronics which combine the velocity and  height informa-
 tion.

 Velocity  Meter
 As  pictured in Figure 1,  two ultrasonic transceivers  are  affixed  to  the
 pipe wall,  one upstream  from the  other.   Pulses of ultrasonic  energy are
 generated  by  one transceiver and  received by the other.   These  pulses
 have the  shape of  a wave  packet as  shown  in  Figure 2  and  are generated
 as  the response of a  piezoelectric  crystal to a spike of  input  voltage.
 The voltage spike  causes  a momentary mechanical construction of the
 crystal.   The crystal  then vibrates to  rest  at its natural frequency
 which  is  in the ultrasonic range, selected for this project to be 400 kHz
 The pulse  generated thereby propagates  through the liquid across the
 pipe to the other  transceiver.  When the pulse reaches the receiving
 crystal, it generates an output voltage waveform also shaped much like
 that shown in Figure  2.  In operation, a received pulse electronically
 triggers the generation of another transmitted pulse in a "sing-around"
 fashion, creating a self-sustained pulse frequency, f.  If electronic
delays are small, the period of this frequency is just the time re-
quired for an ultrasonic pulse to travel through the fluid from trans-
ceiver to transceiver.  If the distance across the pipe between the

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                              SECTION III

                             INTRODUCTION

PURPOSE AND SCOPE
Wastewater flow measurement with adequate accuracy, rangeability and
reliability is the keystone of wastewater regulation, namely the exercise
of control over sewage quantity, rate of travel and routing in the sewer-
age system.  Among other benefits, effective regulation of a combined sew-
age system minimizes outflow of raw sewage during storm conditions.  How-
ever, effective regulation requires effective flow measurement, and the
state-of-the art of instrumentation for sewage flow has been decidedly in
arrears of metering technology developed for other applications.  Thus
the primary purpose of this demonstration was to advance a practical, low
cost, wide range sewage flow measurement technique for general use in
existing storm, sanitary and combined sewers.

In a sanitary sewer system with minimal ground water infiltration, flow
is reasonably steady and present metering practice requires measurement
of volume flow using a pressure head producing device such as a flume or
a weir.  Open channel metering structures of this type are subject to
debris and sedimentation accumulation and importantly, require loss of
pressure head for operation.  Present practice for the measurement of
pressure head in these devices corresponds to the use of either bubbler
gauges or float level gauges, either of which are subject to fouling due
to stringy, greasy and sticky entrainments.  In any of the metering
structures presently employed for volume flow measurement the devices
are unidirectional and subject to very large errors under conditions
of submergence or nongravitational discharge conditions.  In a storm
sewer, or a combined sanitary and storm sewer system, flow is subject
to transients in level and velocity due to rainfall runoff with occasional

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  transceivers  in Figure 1  is  , and the velocity of  sound in the metered
  liquid  is S,  travel time  t is given by /s.  For fluid at rest, this
  travel  time is the same for pulses moving in either direction.  However,
  if the  fluid  is in motion, then the travel time tfl  for pulses moving
  downstream is shortened because their transit is aided by the fluid
  motion  and,
                      'd         -      ~                              (1)
                            S + v  cos 0
                                 c
 where VG is the average fluid velocity along the transmission path or
 chord between the transmitter and receiver,  and v  cos 0 is the
 component of VG in the direction of pulse propagation.  Pulses moving
 upstream travel more slowly because their transit is opposed by the
 fluid motion,  thus the upstream travel time,  t ,  is
                     t  - _____i	
                      u ~      -(2)
                           S  - v  cos 0
                                c
 Assuming  negligible  electronic  delays,  the  related  sing-around  fre-
 quencies  are  the  inverses of  their  respective  transit  times, or
                          S + v  cos e
                    f  - 	E	
                    fd          I(3)

                          S - v  cos 0
                    f		
                     u ~        I(4)

Flow velocity information is provided by the difference between these
frequencies:

                    A-F   f    e     2 COS 0   -
                    At - t  - f  =	v                       ic.\
                          d    u       H       c                      (^>

In any given installation,  0 and I are constants, thus Af is proportional
to the average fluid velocity along the line joining the transceivers.

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In its basic form the metering concept is quite simple.  A beam of
ultrasonic energy is directed through the sewage transport media in
such a manner as to permit the determination of the average of the stream
velocities along the beam.  (It is shown that with proper placement and
under reasonable conditions this average path velocity is nearly equal to
the average of the stream velocities taken over the entire flow cross
section.)  A separate beam of ultrasonic energy is directed down through
the air toward the surface of the sewage transport media and its echo
detected, permitting an accurate determination of the depth.  The depth
(which is directly related to the flow cross section) and average
velocity are then functionally combined to yield flow volume per unit
time.

OBJECTIVES
The following five objectives were set for the demonstration before it
began:
1.    The key objective of the project is to demonstrate the performance
      of new sewage metering equipment which is of sufficiently low cost,
      to achieve general use,  which can be conveniently installed in
      existing sewers, which requires minimal maintenance and is suited
      by design to long term operation in the sewer environment.
2.    Verify the performance,  design, installation and operation of an
      ultrasonic sewage meter by equipping and monitoring two existing
      sewers in the Milwaukee Sewerage System, one 12 feet in diameter
      and the other 5 feet.
3.    Compare the performance of the ultrasonic meter, with respect to
      flow reproducibility and ease of installation with other metering
      devices presently installed in the system, electromagnetic meter-
      ing in the case of the 12 foot diameter conduit and float/Kutter
      formula metering in the 5 foot channel.
4.    Characterize mathematically and by computer solution the relation-
      ships between average volume flow,  level, chordal velocity,  and

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 As described in Appendix A (Velocity Profile Analysis) ,  this average
 velocity along the ultrasonic beam crossing the pipe, v ,  can be related
 to the average velocity, v, across the entire flow cross the entire flow
 cross sectional area if flow is in either the laminar or turbulent regimes

 In practice,  the Af of equation (5)  is a very small number,  too small to
 be measured directly with much precision.  For example,  the  velocity of
 sound in water is about 1500  meters  per second,  and in a pipe one meter
 in diameter carrying water flowing 2 meters per  second,  this frequency
 difference is:

       Af = fd " fu = 563'195  - 561.805 = 1.39 Hz                     (6)

            where  9 is taken as 22.
 For  this reason,  each sing-around  frequency is multiplied  by a  constant
 M  which  is usually about 100.   For M = 100,  Af becomes 139 Hz in  this
 case.  In operation,  the meter measures Af  by counting f  for a period
 tc,  and  counting  f^ for  a like period and subtracting the  two counts.
 This  count difference AN is proportional  to  Af and  is given  by

                     AN = MAf  t =  M  2  cos 9  - v
Taking t  as 2.5 seconds, for the above example,

                    AN = 100 (1.39)   (2.5) = 327.5,                   (8)

and AN is sufficiently large to be measured easily with good precision.

Electronic Signal Processing - With the probe switch in the position
shown in Figure 3,  the upper transceiver is transmitting pulses upstream
and the lower transceiver is receiving ultrasonic pulses from the stream.
The generated sing-around frequency is f  if there is zero flow and f  if
                                        0                            u
there is flow in the direction shown.   The frequency multiplier multiplies
                                   11

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             Ultrasonic
              Transceiver
Pipe Wall
Figure 1.   Ultrasonic Pulse Propagation Path
           Between Transceivers
               2.5 microseconds
Figure 2.  Wave Shape of Ultrasonic Pulse

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 the manhole to minimize chances of fouling during surcharging.  Any
 echo time shorter than that expected for a full conduit (such as would
 occur during surcharging)  is interpreted the  same as that received
 when the conduit has just  reached its 'full' point.

 The combined height gauge  and velocity meter system  is shown in a sketch
 (Figure  4)  of one of the sewer installations carried out as part of
 this demonstration.   It is important to understand that although four  sets
 of  velocity transmitter-receiver  probes are  shown, only one such set is
 required  in a typical  installation.   The extra  sets  were installed  as  a
 means of  verifying  the  validity of using a single  transverse  velocity
 average to  represent the average  velocity of the entire flow  cross  section.
 (The validity of  this procedure is discussed at length  in Appendix  A.)

Velocity-Height Combination

For a circular conduit, the relationship between depth  (d), radius  (r)
and flow cross-sectional area  (A)  is given as

      A = Trr2 (y + i- [ sin~1(x) + x /1-X2 1}
               ^-   TT **                    J
                                                                      (9)

where x is given as  (d/r-1).

Although the height gauge provides a measurement which is actually pro-
portional to the 'distance-to-product', this can be translated using a
digital electronic scheme to be proportional to the flow cross-sectional
area A.  A voltage proportional to this area is then used as the supply
voltage for the binary ladder in the relay memory.  The output of the
relay memory is thus proportional to the product of the average trans-
verse velocity v  and the flow cross section area A.
                                  13

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N/
' / \
S. V/ if J
^ X o
J / U
/<



OUTPUT
* CONVERTER

^
^ 
PROBE
OUUIT/*LJ _
5>wi I un f
. Q_ T
 H *VJ
U.
L-o |
u A



4
^






TRANSMIT fo FREQUENCY fo. M
RECEIVE * MULTIPLIER
1^

TIMING & 4 QSC
T CONTROL
1
RELAY . UP-DOWN
MEMORY * COUNTER *
1 r
DIGITAL
INTEGRATOR ^
Figure  3.  Block  Diagram of Meter  Electronics
                                                REMOTE
                                            INSTRUMENTATION
Figure 4.
Meter Installation in a
Sewer for Measurement of
Wastewater.
                                     10

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 The  pipe  friction  coefficient  X  is generally between  0.01 and  0.06
 so,  for a full pipe on a major chord,

                    0.9023  < k <  0.9577                               (17)

 depending upon the value of X.   k is the constant by  which VG must
 be multiplied to yield v.

 Since a similar equation does not exist for partially full circular
 conduits,  it was necessary to examine experimentally  obtained data
 for  such  conduits  to determine the k-factor ranges.   The reduction of
 this data for partially full circular pipes has indicated that a value
 of k of 0.96 is typical over a significant portion of the cross section
 when chordal velocity averages are obtained for planes parallel to the
 surface plane and  between 30% and 70% of depth.  (This is presented in
 more detail in Appendix A.)   The  constant k is incorporated into the
 scaling electronics along with the scaling multiplier for engineering
 units and  the cross section area multiplier for calculation of Q.
 In general:

                    Q = Av = Ak VG                                    (18)

 These constants are taken into account when the electronics are set
 up for a particular installation.  The adjustments are made by
 appropriate strapping of elements in binary counting chains and are
 accomplished by either soldering or not soldering jumpers in the
 standard unit.

The applicability of the above k-factor for calculation of Q depends
upon the existence of a fully developed velocity profile of a
reasonably predictable form.  The transceiver mounting site should
therefore have  10 to 20 straight diameters upstream and be sufficient-
ly distant from elbows,  constrictions,  expansions and pumps.   When these
                                   15

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the  frequency by M.  An oscillator generates a clock rate for the timing
and  control circuits,these in turn provide various multiples of the clock
rate for controlling the probe switch and resetting the frequency multi-
plier and up-down counter.  The probe switch is reversed every t  seconds,
                                                                c
thereby reversing the roles of the transceivers and alternately generat-
ing  f^ and f .  During each such cycle, the up-down counter counts up to
Mf^  and then counts back down to Mf  .  The number remaining in the counter
after such a cycle is the AN defined in equation  (7) and is proportional
to Af.  The value of AN is stored in the relay memory after each cycle
until it is updated by the next measurement cycle.  For t  equal to 2.5
seconds, the count stored in the relay memory is updated every five
seconds.  In digital binary format in the memory, the count is converted
to an analog output current proportional to flow rate by means of a seven
element ladder circuit in the output converter.  The clock rate from the
oscillator is digitally multiplied by the binary number in the relay
memory representing flow rate and sent to an eleven element binary counter
in the digital integrator.   Elements of this counter can be "strapped" in
or out of the counting sequence so as to scale the integrator output to
convenient engineering units of quantity, i.e., cubic meters, gallons,
acre, feet, etc.  Similarly,  binary elements in the frequency multi-
plier and relay memory can be strapped in or out to select the proper
value for M and full-scale respectively.

Height Gauge

Conceptually this unit is much the same as the velocity meter except for
the  following:   The burst frequency is about ten times lower (40 kHz),
the  burst repetition is preset to permit the reception of the echo
from the greatest distance desired (generally the bottom if and when
the channel is empty),  differences in the sonic velocity of air are
corrected for by monitoring the air temperature and making an offset
linear correction to the echo time measurement and a single transmitter-
receiver head is used.   This  transceiver unit is placed several feet up
                                   12

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                  IJJ  i  i  _
Figure 5.  Meter Electronics Unit
                  17

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Average transverse velocity versus  average  area velocity - For the


case of a circular conduit running  full,  the  flow velocity v at any


point on the logarithmic velocity profile associated with turbulent


flow at a distance x  from the  axis  of  the pipe  of radius R is
                    v = v    +  2.5 v*  In	 ,                   (10)
                         max                R
and
                    v* = v  A/  =  "friction  velocity"            (11)



                    where X = pipe friction  coefficient.


Using  (11) and integrating,



                            R



                    v    I  v 2ir x dx = v    - 3.75  v*             (12)
                       2  I               max
                     7TR  )
                    v  =       v dx = v    -  2.5 v*                (13)
                     c   R   I          max


                            0


Therefore:
                    v  (1 + 3.75 A      ) = v                        (14)
                                   8       max
and
                    v = 	-=^                            (15)


                        1 + 3.75
Dividing v by v  yields:
                                         r-,  = k
                    v      1 + 0.44194
                     c
                                  14

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SEWERAGE COMMISSION
     Mop
        and
       Active
          LOCATIONS
       Figure  6 .   City  of Milwaukee Sewerage System Map
                                19

-------
 criteria are met,  the calibration has been  shown to be adequate and
 accurate.

 Electronic output  - the electronic unit pictured in Figure 5 contains
 all of the digital signal processing circuitry mounted on individual
 plug-in printed circuit cards, as well as the power supplies and data
 readout equipment.  The level unit provides a 0-10 volt signal pro-
 portional to the distance to the surface.  This signal is processed in
 the velocity electronic unit to provide the voltage V  proportional
                                                     a
 to the fluid cross section area.  The flow signal,  generated in the
velocity electronic unit is a 4 - 20 mADC output current proportional
 to flow rate.  The output signal generated by combining the velocity
and area signals is suitable for telemetering and driving remote read-
out equipment.   Circular and strip chart recorders, magnetic and
punched paper tape recorders, and remote totalizers can be provided
for this purpose.
                                  16

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             VICINITY OF TrtC CAMMlfr4& AVC.




             &ffitTQL u-N.MORRIS E
-------
                                SECTION IV
                               INSTALLATION

 SITE LOCATIONS
 Two sites were initially selected as representative combined storm-
 sanitary sewers.   These were the Cambridge Avenue Site  located near
 the village of Shorewood in the near north metropolitan Milwaukee
 area,  (see Figure  6)  and the South Shore  Plant  Site on  the  far south-
 southeast side.  Later  in the demonstration project the College Avenue
 Site was selected.   This third location was upstream a  mile or so  from
 the South Shore Site  and eliminated difficulties  experienced due to
 abnormally high loadings contributed by a glue  factory  located next
 to  the  South Shore  Treatment Plant.   (This is discussed in  detail
 later in the report.)

 Cambridge Avenue
 A sketch of  the Cambridge  Avenue  Site was used  earlier  (Figure 4)  as
 being typical  of a  meter  installation in  an existing  sewer  (except
 that only one  set of  velocity  probes would  usually  be required).   This
 location has a 60 inch diameter circular  conduit  located approximately
 30  feet  below  the surface.   (See  Figure 7).  The  metering site  is  1202
 feet downstream from  an  existing  weir and float type monitor,  542  feet
 downstream from the junction with another  smaller sewer and about  one-
 third mile upstream from the junction with  an inverted  siphon.   It  is
 known that at  times of high  flow, some back-watering and surcharging
 does occur due to the inverted siphon, and  hence  the validity of the
 measurements based on level only would be suspect.  Head diagrams  for
 the vicinity of this  site are  included as Figure  8.  A flow record,
 based on  the weir and float data located upstream of the ultrasonic
metering  site, as well as the  39  inch East Providence Street sewer
                                    18

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                         MONDAY
                             NOON
Figure 9a.  Flow Recording - 60" Cambridge Ave. Sewer
                             23

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                                                       COMMI55ICK4
                                              PROPOSED
                                            CAMBRI04 AVC.
                                           ULTRASONIC
                                                StCT. A-A
                                               OCTAIi.  Of
Figure 7.   Location and Configuration of  the  60" Cambridge Avenue Sewer
                                  20

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 outfall,  is  included as Figure  9-   Two 7-day charts  showing the ultra-
 sonic  flowmeter recording and flow upstream of the ultrasonic metering
 sites  are included as Figures 9a and 9b respectively.  Naturally these
 flow quantities would be somewhat lower than would be expected at the
 ultrasonic metering location since they do not include all flows which
 reach  that site.

 South  Shore
 A survey sketch of the influent channel at the South Shore Plant is
 shown  in Figure 10.   This is a 12.5 foot diameter circular conduit
 at the location of the velocity probe installation which is 60 feet
 upstream from the plant  inlet section.   A transition section begins
 36 feet downstream.   The height gauge transceiver was placed at the
 inlet bay so  as to be more  accessible and  better  protected in the
 event of surcharge.   Mag meters  are located downstream of the bar  screens
 which are located  immediately downstream from  the inlet bay.   It was
 anticipated that  these would be  used  to assist  in evaluating the oper-
 ation of the  ultrasonic  system.

 A  profile drawing  of  the  sewers  in  the  vicinity of  this  site  is shown
 in Figure 11.   Note the proximity of the Peter Cooper  Corporation  (glue
 factory)  outfall and drop pipe.

 College Avenue
 A  detail  of the manhole and  sewer at College and  Pennsylvania Avenues
 is shown  in Figure 12.  At this location the sewer is a 12 foot diameter
 circular conduit.  The average dpeth of flow is 3 feet with a maximum
depth of 8 feet noted following a heavy downpour  in 1972.

INSTALLATION DETAILS
There are several ways in which the velocity probes can be installed
in  a  sewer. On steel  conduits,  they can be clamped on externally.
                                   25

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Precip-
itation
(Inches)
   0.30
   0.10-
               n
,-n
                60" Sewer - Cambridge $ Newpojrt Ave.
                                                             Data From
                                                             7-Day Chart
            Flow in 54" Sewer Up$tream of
            Providence Ave. Connection (See Fig. 8).
            "0" Computed From Depth of Flow
                                        Data From
                                       7-Day Chart
                                        Fig. 9-b
                   NOTE:  The Difference Between the Above
                   Flow Rate Values Corresponds to the Estimated

                   Values of the Flow in the.Providence Ave. Connection
                         2223 2425 26 27 26                6  7 8  9  10 II  12
         15  16 17 f8 19 2O 21                  29 30  I  2 3 4  S
                    September                           October



        Figure 9.  -  Comparison of  Measurements  - Ultrasonic vs  Level  Only.
                                     22

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                                                                           c
                                                                          H

                                                                           M

                                                                           (D

                                                                           0)



                                                                           O

                                                                           0)
                                                                          i-H
                                                                          H
                                                                          M-l
                                                                           0
                                                                           O
                                                                           t-l
                                                                           a
                                                                          H
27

-------
    o
    o
    m

    ro

    CN

    rH
    o
    O
    O
    O
    O
    o
    o
    o
Cn
    o
    o
    o
    o
    n
    o
    o
    in

    o
    CM
    on
    o
    o
    o

    09
    r-
    m
     U
                                                                                                         I
                                                                                                   HOONG
                                                                                                               in
                                                                                                               r-
                                                                                                                I
                                                                                                               o
                                                                                                               m
                                                                                                               oo
                                                                                                               m
                                                                                                               r^
                                                                                                                I
                                                                                                                I
                                                                                                               O
                                                                                                               oo
                                                                                                                     o
                                                                                                                     4->
                                                                                                                    H
                                                                                                                     W
 0)


4

 0)
 tP
T3
H
 VI
                                                                                                                    u
iw
 o
 0)
 ^
4->
 W
 04
D

 M
 0)
 5
 Q)
CO
^
in
                                                                                                                     O
                                                                                                                     O
                                                                                                                     0)
                                                                                                                     Pi
                                                                                                                     CP
                                                                                                                    H
                                                                                             ro
                                                         24

-------
        Figure 13.  400 kHz Ultrasonic Transceiver
Figure 14.  Multiple Probe Mounting Configuration
                          29

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                                                                  cn
                                                                  0
                                                                  VI
                                                                  ITS
                                                                  4J
                                                                  (1)
                                                                  a
                                                                  o
                                                                  H
                                                                  -P

                                                                  0

                                                                  s
                                                                  o
                                                                  H

                                                                   0)
26

-------
 Installation diagrams for  each of the  sites  are shown in  Figures  15
 (Cambridge  Avenue),  10 (South Shore) and  16,  17 and  18  (College Avenue)
 It  should be noted that  the  two probe  sets used at the College Avenue
 Site were the top two sets  (of six  sets)  from the South Shore Site.

 The height  gauge at College Avenue  was also obtained  from the South
 Shore Installation.   Note that  the  level  sensor was not positioned
 directly over the sewer center  line since it was necessary to mount the
 sensor in the manhole  (see Figure 16).   This was judged to be satis-
 factory since the flow level is never so low as not to present an
adequate reflective surface directly below the level  sensor.
                                 31

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                             SEWERAGE COMMISSION
                             MGASURlKjq STATION! - COLLEGE 4
                                 STANDARD MANHOLE.
                                 FRAME < COVE-.
                                                        -SUNOAP.O MJWOLE
                                                        COVER
                                                                 R\M EL 134. 
                                                   O.C.
                                               .  QO-STIPS E
                                           3;=_=vJ 4-S1TIP* 3
                                                . 8-U t3 W
f f            ,   .   "       rt  2T ^
II	FLOW UNC BL.MI.93    L-\'''"
                                                .  -
                                          , Ft. jL^ JVSC. PIPE IM33
     l ALL  ST'L SHAFT
Figure 12.   Detail of Manhole and Sewer, College  Avenue
                                       28

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                          PLAM
                                        ELEVATION VIEW
                                                 A.A
Figure 16.   Ultrasonic Probe Mounting Configuration, College Avenue
                              33

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Where block-outs exist they can be installed flush with the inside
surface.  Finally, where neither of the first two methods are practi-
cal, they can be affixed to the inside of the conduit.  Due to the site
characteristics at all three locations this third technique was selected.
Furthermore, to facilitate the alignment, the transceivers or probes
were housed in hydrodynamic shields mounted on curved plates which were
then affixed to the interior wall of the sewers.  Typical fixtures are
shown in Figures 13 and 14.  Wires from the transceivers are carried
to a junction box and then to the electronic unit.  The spacing between
the transceivers on the pipe is first calculated and then confirmed by
both physical and electronic measurements, taking into account the propa-
gation of the sound pulses through the plastic material encapsulating the
transceiver crystal and through the metered liquid.  The path angle
through each medium is governed by the velocity of sound in each medium
according to Snell's law:
                        Sln 91 _ Sin 92                               (19)
                         Sl    "   S2
where        Q-i and 92 are the path angles in the transceiver
             and the liquid respectively
             S^ and S2 are the velocities of sound in these
             respective media.

From a knowledge of the sewer dimensions and probe spacing, a zero flow
sing-around frequency f  is calculated.  When the transceivers are
fixed in place, the actual zero flow signal is measured and compared
with the calculated value.  If these two agree within 1%,  the installation
is  judged satisfactory and the output readings correspond  to actual flow.
This procedure has been verified in a large number of actual installations.

For most sewer installations in the sizes commonly encountered  (1 foot
to  15 feet and larger) Reynolds numbers are well into the  turbulent range.
                                    30

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Figure 18.  view Looking Upstream, Ultrasonic Probe Installation,
            College Avenue
                                 35

-------
                                                    or TO
                                               Menu VAUCf
                    PLAM VIEW
Figure 15.  Ultrasonic Probe Mounting Configuration, Cambridge Avenue
                                   32

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))DH
R
X


LEADING
CIW*C
CD6fc
DETECTOR


ASMV


TX
       Figure 19.  Basic Unit, Receiver-Transmitter
               Figure 20.    Ultrasonic  Pulse Packet
RESET
ASMV OUTPUT
VOLTAGE
SFT
RECEIVER
TRANSMITTER
PULSE TIMING




RX' Tx

i
1
s
RX-TX
                                                     FREE  RUNNING
                                                     RESET TIME
               Figure 21.  Timing Diagram
                              37

-------
Figure 17.  Detailed Plan View, Ultrasonic Probe Mounting Configuration,
            College Avenue
                                   34

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  7
                     xiu
 ec a
<  H-
UJ  Ul
o.  o

                 >- o
                 UJ C9
i
H


                                              H

                                              M-l
                                              H
                                              (N

                                              CM
                                              CP
                                              H
                 39

-------
                                SECTION V
                          OPERATION & EVALUATION
 Early  in  the  operational  phase  of  the  demonstration  program it  be-
 came evident  that  there were  significant  fluctuations  in  the received
 signal  strength, caused by  variations  in  the  attenuation  character-
 istics  of the fluid  transmission medium.   Due to  the nature of  the
 Leading-Edge  detection scheme employed in the receiver-transmitter
 block of  the  basic unit  (see  Figure  19),  these random  amplitude
 variations resulted  in random frequency modulations  of the  upstream
 and downstream sing-around  frequencies generated  by  the Astable
 Multivibrator (ASMV).  Occasionally  a  transmitted pulse was not re-
 ceived  at all, and in such  a  case  the  ASMV would  time-out to  its
 natural period termination  point,  injecting a  large  error in  the
 sing-around frequency determination.

 The difficulties with utilizing Leading-Edge detection can  be seen
 by examining  again the ultrasonic  pulse packet as shown in  Figure 20.
 If the detector level is  set  so as to  detect any  voltage excursion
 which exceeds  level V-j_, then a received pulse  is  detected at time tlf
 as shown.  This means that  for a fluid with both  uniform and constantly
 homogeneity each pulse packet will be detected at the  same point in
 time within the packet.  However,  should the packet  shown be attenuated
 by 50% on occasion, the pulse packet would not be detected until time to.
 This injects a time error of about 2.5 micro-seconds into the determination
of the sing-around period (see Figure 20).  In the installations being
 tested this could amount to more than a full scale error in the
determination of channel  velocity,  depending entirely on the random
nature of the amplitude fluctuations.

                                    36

-------
  turbulence  to reflect the ultrasonic beam at an angle outside the
  reception area of the transducer.  Consequently noise spikes occur in
  the output  signal.  Additional damping was externally added to reduce
  this problem.  Another possible drawback to this single transducer type
  of unit is  the need for a dead zone of about three feet from the trans-
  ducer face  in which no echo can be detected.  This region is blanked to
  allow the transducer sufficient time to damp oscillations remaining
  from the transmission burst.  A new type of ultrasonic system presently
  under development will eliminate this drawback.

 Velocity Meter Probes
 The ultrasonic beam was  measured in a tank of clean water and found to
 have a transmission cone having an included angle of approximately  8
 degrees.   For the Cambridge  Avenue site this  means good  reception with-
 in a 3 inch radius about the receiving  transducer.   Good reception  with-
 out interference  from surface absorbtion or  reflection can be  obtained
 when the probes are  submerged at  least  2 inches.   For the clean water,
 an attenuation of approximately 5  db  per foot was  observed, with  the
 probes operating  at  400  kHZ.   This attenuation  was  independent of trans-
 mitter power.

 Automatic Trigger Control  (ATC) Performance - As discussed earlier, the
 electronic portion of the velocity meter was modified to  include  a cir-
 cuit which would  automatically  insert a phantom trigger should the trans-
 mission path be momentarily occluded.  The insertion  time is based on
 that for the last received pulse.  A test of the ATC  system was made
 under a variety of conditions.  Transmission in a channel 10 feet wide
 was simulated, with a full scale velocity representing 10 feet per second.
 The results  of the test are summarized in Figure 23.  Note that erroneous
 velocities of relatively stable appearance are generated when the missed
 pulses are symmetrically distributed both upstream and downstream with-
 out the ATC operating.  When the symmetry is broken by randomly
missing a group of pulses there is incoherence in the output  without
                                   41

-------
The difficulties with triggering the ASMV and transmitter directly
upon detection of a received signal becomes apparent upon examination
of the ASMV function.  The timing diagram shown in Figure 21.   Note
that the free-running period of the ASMV is so set that it is  in a re-
settable mode well before the time range in which a received pulse
might occur, and will reset itself automatically well after the probable
received pulse time range.  Since the transmitter is fired upon reset
of the ASMV, the self-starting capability of the entire unit is ensured.
However, should a received pulse packet be so severely attenuated so as
not to be detected, an extremely large time error, and hence frequency
error, is injected into the system, and indeed such errors were observed.
It was thus obvious that an alternative to Leading-Edge detection was
necessary and that some substitute trigger mechanics had to be provided.

Close study and evaluation of the ultrasonic pulse packets being re-
ceived indicated that, although the sewage medium did randomly attenuate
pulse packets in varying amounts, all oscillations within any  one packet
were generally attenuated by the same amount.  Consequently, it was deter-
mined that detection of the peak of the pulse packet envelope  would provide
more stability.  Using this scheme, relatively rapid fluctuations in the
envelope would not be detrimental and by adding automatic gain control  (AGC)
long time constant changes in amplitude could also be tolerated.  The AGC
also ensured that the pulse packet envelope would not have a slipped top
due to over-driven receiver amplifiers.  Since the pulse packet envelope
existed for only 1% of the total "listening" period, the AGC had to be
of the "keyed" type, i.e., only the amplitude of the packet envelope
itself would be "checked" to determine any gain correction.

The remaining problem of automatically triggering the transmitter and
resetting the ASMV without undue delay in the event of a missing re-
ceived pulse involved more effort.
                                    38

-------
  the ATC operating.   This condition most nearly simulates the actual
  sewage channel environment.   in all cases,  accuracy and coherence are
  maintained when the ATC is operational.

                              _  An evaluation of the  effects of suspended
  solids  on  the  performance of  the  velocity measurement was undertaken
  both  in the  laboratory and  in the field.  Field evaluation was more
  qualitative  than quantitative in  that precise determination of the
  variables  involved was difficult  at best.  For comparative purposes a
  quantity equal to the product of  the solids loading in milligrams per
  liter times  the ultrasonic transmission path length in meters divided
  by 1000 was  used.  For future reference this product will be called the
  Load-Length  Product (LLP) .   On typical days the LLP ' s were determined
  at Cambridge Avenue,  South Shore and at Jones Island.   These were de-
  termined to be 0.192,  0.735 and 1.357.   Of interest was  the fact that
  the ultrasonic transmission at Cambridge Avenue Site  was uninterrupted,
 at the South Shore  Site  the transmission was  hopelessly  occluded and  at
 Jones  Island the  transmission  was  only  intermittently  blocked.   Further-
 more,  the transmission path  length at Jones Island  was a full  foot
 longer.   Clearly  the LLP  was not by itself an adequate indicator  of
 probable performance capability.   Other  variables considered were:
 particle size,  density of particles (number per unit volume) and  particle
 density  (weight per unit  volume) .   Although an exact theoretical  or
 experimental  treatment which includes all these variables would be
 essentially impossible, the following treatment is of such a nature
 as to  indicate  their general effect on the transmission intensity.

 Consider a region in which there exists a number of spherical scatterers
arranged in such a manner and with such separation as to  preclude ex-
tensive multiple scattering.   The incident wave  attenuation in this'
region is given by the  equation

                    Xi  =  Tio  exp {~ N
                                   43

-------
In this case an analog scheme was employed in which a ramp voltage
was generated at the time the ASMV entered the "set" mode and the
voltage which existed at the time at which a pulse was received was
held.  During the next cycle the ramp voltage was compared to the
value held and if it exceeded that value, caused a surrogate trigger
to be injected.  To ensure an adequate capture capability in the
event of a reduction in the sonic velocity, a small delay was in-
serted between the detection of a pulse packet and the triggering
of the transmitter.  Additional noise rejection was obtained by blank-
ing the receiver detector during the period for which the ASMV was in
the "set" mode.

The block diagram of the stages in the modified receiver transmitter
block is shown in Figure 22.  Laboratory tests of the modified
system under ideal conditions resulted in less than 1% error when 9
out of 10 pulses were absent and there were no detectable effects
when the input signal amplitude varied over the full range allowed by
the receiver gain-control potentiometer.

GENERAL ANALYSIS OF EQUIPMENT OPERATION
In the following sub-sections operational characteristics of physical
elements of the flowmeter system are presented followed by discussions
of environmental factors, such as solids loading and air entrainment,
and their effects on the operation.  Finally, specific data obtained
at each site is presented.
The electronic unit used to sense the liquid level was the Bin-Dicator
Level Data LC-520 control with transducer LT-A and temperature
compensator  (South Shore installation only).  The claimed electronic
accuracy of   1% of full scale vyas met or exceeded.  However, the  re-
sponse of the unit is somewhat faster than  desirable, even when operat-
ing in the "Delayed" mode.  It is possible  to have sufficient surface
                                    40

-------
  relating intensity to scatter site density it is easy to predict total
  occlusion at the site.  Thus it was discovered that entrainment of verv
  small air bubbles was the cause of blocked transmission and not suspended
  solids loading.

  To complete the  study,  a  laboratory study of  the effects on transmission
  by various  materials  was  made.   The results for  several  representative
  types of  materials are  presented below.   Note particularly  the  values
  of the LLP's.

                                                  Occlusion
       M .  .  .                    Density            Length
       Material           (Milligrams per liter)  	(Meters)          LLP
    Rubberized
    Horse Hair                   19 595
                                ^'^^              0.305          5.984

   Open-Cell
   Plastic Foam                 20,620              0.0658         1.357

   Cotton Toweling             265,150              0.015          3.977

 In a separate study performed on return sludge of controlled densities,
 the Japanese have determined that the LLP  should  be  less  than 5.0 to
 ensure operation  for this  equipment.   Note that this  figure  is bracketed
 by the horsehair  and cotton toweling LLP's which  are  probably representative
 of the textural quality  of part  of domestic sewage.   From both studies
 it would appear that the criteria should be that  in the absence  of
 entrained  air, the LLP should  not exceed 5.0

 Effects_of Entrained Air - Following up on the observation that  entrained
 air had an enormously deleterious effect on the ultrasonic transmission
 quality, a series of experiments were performed in the laboratory.  Al-
 though not intended to be highly refined or conclusive, the results are
of  interest.   The 400 kHz probes used in the equipment were placed in
clear water approximately two feet apart and the transmitter  probe was
                                   45

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                                       FULL  SCALE
1.  NO MISSING Rx PULSES.
2.  RANDOM PERIODS MISSING  1 OUT OF  EVERY  10  Rx
    PULSES, ATC 'ON1 (PHANTOM PULSES INSERTED).
3.  AS IN 2, EXCEPT ATC  'OFF1 (NO  PHANTOM  PULSES  INS.).
if.  RANDOM PERIODS MISSING  9 OUT OF  EVERY  10  Rx PULSES
    ATC 'OFF'.
5.  AS IN **, EXCEPT ATC  'ON1.
6.  MISSING 1 OUT OF EVERY  10 Rx PULSES  AT ALL
    TIMES ATC 'ON'.
7.  AS IN 6, EXCEPT ATC  'OFF'.
8.  MISSING 9 OUT OF EVERY  10 Rx PULSES  AT ALL
    TIMES ATC 'OFF1.
9.  AS IN 8, EXCEPT ATC  'ON1.
         Figure 23.  ATC Performance Test
                         42

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Figure 25.

Received Signal,
Water with Entrained
Air Bubbles
                                                   Figure 24.

                                                   Received Signal,
                                                   Clear  Water
               I  '  .         '
Figure 26.

Received Signal,
Clear Water, Expanded
                                     47

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here I   is the initial incident wave intensity,  N is the number of
      io

scatters per unit volume,  x is the distance into  the region and the


Z  and E  are defined as the scattering and absorption cross sections
 s      a

respectively.  These cross sections are defined as the ratio of the


power scattered (or absorbed)  to the incident intensity.
The initial incident intensity I   is given as
                    T    	
                     io     pc




Where A is the amplitude, p is the density of the medium and c is the


propagation velocity in the medium.




One author has indicated that the Z  term is proportional to N for


particle sizes large compared with the wave length and to N^ for those


small compared with the wave length.  In either event, this yields an


attenuation relationship of the form.



                                ]^
                    I. ^ exp  (KN )




where 2
-------

-------
 in diameter with four"sets of probes placed at the 1.0,  1.75,  2.5
 and 3.25 foot levels.  Probe face-to-face separation are summarized
 in the Table below.
             Probe                Level                Separation
             Set #                (feet)                 (feet)
              1                     3.25                  4.54
              2                     2.50                  4.88
              3                     1.75                  4.54
              4                     1.00                  3.88
 The velocity unit  is  calibrated  for  the  separation  found at both
 sets #1  and  #3  and for  a maximum or  full-scale velocity of 5.5 feet
 per second.   (The  estimate  is based  on slope and typical flow data
 supplied by  the Milwaukee Sewerage Commission.)  Using  the unit in
 flow rate (Q) mode by integrating  the level data as discussed in an
 earlier  section, the  full-scale  value is Q = 70 mgd  (i.e., a velocity
 of  5.5 fps with a  level of  5.0 feet).

 Of  interest  is  a plot (see  Figure  30) of the normalized area of a
 circular  conduit,  versus the depth of flow (normalized  to the radius
 of  the conduit).   It  was surprising  to note that a least-squares fit
 of  a  linear  approximation would  result in a maximum error of less than
 5%.   And  over the  level range of 0.1 < h/r < 1.9, constituting 90% of
 the range and over  99% of the occurrences, an error of less than 2.5%
 can be realized.   For this reason,  the Cambridge Avenue unit has been
 calibrated using an off-set linear approximation of the latter type.

 As a check on the  flow profiles anticipated from theoretical and
 observed data, the probe sets of this site were strobed manually and
 over a period of several minutes average velocity data was obtained
 at each of the lower three sets.   The level was 3.10 feet during the
 test which occurred at 0830 on March 9,  1973.   The necessary correction
 factors for probe sets #2 and #4, due to the  different transmission
                                 50
                                   48
density of air bubbles of resonant size would be reduced.  Ultrasonic
transmission in the presence of entrained air at various sonic frequencies
would be a fruitful area for additional investigation.

CAMBRIDGE AVENUE
From the very beginning of the tests, signal levels at this site have
usually been quite strong.  In fact, reduction in receiver and/or trans-
mitter strength was clearly indicated.  Very little difficulty with
entrained solids or air was experienced, and the addition of the ATC
circuit eliminated any occasional traces.  A section of  a typical
chart recording at this location  is  included in Figure 29.  The system
at this location has continued to operate with only routine periodic
maintenance for nearly 2 years.   Installation diagrams for the site
can be found  in Section IV.  Note that  it is a circular  conduit 5 feet
                                    46

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                                      51

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                            rtrmtt
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Figure 31.  Measured Chordal Velocities Versus Depth, Cambridge Ave
            Figure  32.   k-Factor Estimate, Cambridge Avenue
                                      52

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 lengths, were applied and the results are plotted in Figure 31.  By per-
 forming an area integration of VG as shown in Figure 31, an average
 velocity v is determined to be 1.15 feet per second yielding a minimum
 k-factor of 0.97.  Note the close agreement with the value of 0.98
 obtained for open circular pipes in turbulent flow.   (See Appendix A for
 a detailed presentation of the k-factor analysis.)

 Using this value of v (1.15 feet per second)  a k-factor plot is obtained
 and presented as Figure 32.   Note again the close similarity to the
 k-factor plots for the circular pipes as presented  in Appendix A.

 Typical velocities observed  at this site fall in the range of  1.0  to 2.0
 feet per second,  and typical levels between 3.0 and  4.0 feet.   As  such,
 typical flow extremes are  approximately 8 MGD and 22 MGD.   It  is im-
 portant to  note  that these flow velocities are only  20% to 40%  of  those
 predicted by use  of Manning's  equation,  indicating that the energy slope
 is only a fraction of the  channel  slope.   Retardation of the flow  may
 be caused by the  hydraulic characteristics of an inverted  syphon down-
 stream  from the metering site.

 SOUTH SHORE  TREATMENT PLANT

 As discussed in an  earlier section, difficulties were experienced with
 the ultrasonic transmission at this site which were not  fully under-
 stood, until late in  the demonstration grant period, to  be caused by
 entrained air.  Installation diagrams for this site can be found in
 Section IV.   Note that it is a circular conduit 12.5 feet in diameter
with initially six sets of probes installed at the 2.0,   3.75, 5.5,  7.25,
 9.0 and 10.75 foot levels.   Probe face-to-face separations are summa-
rized in the following table.
                                   53

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             Probe                 Level                Separation
             Set #                 (feet)                  (feet)
               1                    10.75                   8.66
               2                     9.0                   11.57
               3                     7.25                  12.78
               4                     5.5                   12.81
               5                     3.75                  11.74
               6                     2.0                    9.19
The velocity unit was calibrated for the separation found at probe set #6
and for a maximum or full scale velocity of 10 feet per second.   Using
the unit in the flow rate (Q)  mode by integrating the level data as dis-
cussed in an earlier section,  the full-scale value is Q = 795 MGD (i.e.,
a velocity of 10 fps with a level of 12.5 feet).   Although the system
did not perform as expected and flow level was low (about 3.0 feet)  most
of the time, some evaluation was possible during a period when the glue
factory was not operating and during which the level could be elevated
by temporarily restricting the plant input volume.

As expected, the 2-week shut-down of the Peter Cooper Plant and subsequent
reduction or termination of its contribution to the South Shore Plant in-
fluent resulted in the ultrasonic velocity meter being 100% operational.
This confirmed the suspicion that the occlusion of the ultrasonic signal
was caused in some way by the glue factory effluent.  Without doubt, this
is not a typical condition which would be expected at most treatment
plants.   During several of these days the input flow at the South Shore
Plant was purposely reduced, backfilling the 12^-foot diameter conduit
to a depth of 6 to 9 feet.  Flow control gates were then opened slightly
permitting numerous sets of average chordal velocity readings to be
obtained.  This data was then plotted and correlated with the chart
recordings of total plant influent.  Although much of the data was ob-
tained during hydraulic transients, graphic interpolation of the results
yields flow values in close agreement with those obtained by alternate
                                   54

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  means  (more specifically the mag meters downstream).  Although cali-
  bration data for the mag meters was not available, the operating engineer
  indicated that they had been recently checked and were as accurate as
  could be expected considering the operating conditions.  Their proximity
  to the ultrasonic unit precluded the need for significant time corrections
  due to lag.   During the greater part of the morning and early afternoon
  of June 6,  1972,  the influent flow to the South Shore Treatment Plant was
  significantly reduced,  backing up the 12h foot diameter conduit to  a
  depth of 6  feet.   Average chordal velocity data at the levels permitted
  by probe locations  were recorded at  depths of 5 feet  (1130  hours) and
  6  feet (1400  hours).  The former exhibited a  typically turbulent profile
  whereas  the latter  did  not,  appearing  more laminar.   No doubt the
  dynamics of the filling conduit  contributed to  the  shape.   Figure 33
  shows  these profiles whereas Figure  34 has the  corresponding  plant  in-
  fluent flow data as recorded by mag meters further downstream (follow-
  ing coarse screening,.  Note that estimates of flow based on  these pro-
  files yield values of 13.6 MGD at 1130 (versus 14 MGD recorded) and 10.2
 MOD at 1400 (versus 11 MGD recorded).

 fit approximately 1510 the butterfly valves downstream were partially
 opened, resulting  in a  rapid flow rate increase from about 13 MGD to 70
 MGD,  followed  by a typically exponential  decay characteristic.  The  gates
 at  the conduit-plant junction permit  flow into the plant from the bottom
 of  the conduit,  hence there  would be  a  reduced flow impedance at lower
 levels.   Although  the velocity  sensing  elements  were located approxi-
 mately  60 feet upstream,  the  physical configuration  of the gates would
 probably result  in some  dynamic effects being  observed even  at that
 distance.

 The butterfly valves were again adjusted at about 1524 increasing the
 flow to 93 MGD briefly.   Note that the effects of these two adjustments
can be readily observed in both figures.  Of course, the extrapolations
are estimates;  however,  these estimates are based on observed flow
                                   57

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characteristics reported elsewhere (Barnes,  et al).   For instance,  a
reverse slope characteristic such as observed at 1515 is also found in
circular conduits having a large slope and consequent high flow.   No
doubt, the shape in this case is due to the gate location, inasmuch as
the profile does tend to stabilize.

Signal strength during the tests was outstanding, a situation due pri-
marily to the fact that the Peter Cooper Glue Factory was not operating
and was not discharging into the conduit.

Flows calculated from the velocity profiles measured by the ultrasonic
meter agreed quite well with those measured by the plant mag meters:
                          Calculated From
                           Flow Profiles
                             Measured                  Mag Meter
       Time               Ultrasonically               Recording
       1515                   63 MGD                     65 MGD
       1520                   66                         61
       1525                   82                         87
       1530                   86                         70

Again it must be reemphasized that these flow tests were run under transient
conditions caused by backing up the sewer and then emptying it, by means
of positioning the flow control gates at the plant inlet and thus are not
entirely representative of normal flow conditions.  Note under these
conditions that flow profiles seem to "pivot" about a point at about 40%
maximum depth, lending additional support to the procedure of locating
a single set of ultrasonic probes at this depth for velocity measurements.

COLLEGE AVENUE
Due to the difficulties encountered at the South Shore Plant and in order
to realize a full-time operating system, the top two probe sets  (#1 and #2)
                                     58

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 of the South Shore installation were  removed  and  located  in a  12  foot
 diameter conduit 120 feet  below the intersections of College and
 Pennsylvania Avenues.   The probe sets #1 and  #2 were located at levels
 of 1.7 and 3.45  feet respectively (inverted from  their previous position-
 ing).   Face-to-face separations of the reinstalled probes are  8.25 and
 11.14  feet for the 1.7  and 3.45 foot  levels respectively.  The calibration
 of the unit was  not changed and hence its use requires a correction
 factor equal  to  the ratio  of the  operational length to the calibration
 length.   Installation diagrams  for this site can  be found in Section IV.

 At this  site  proper  operation of  the  velocity unit was immediately attain-
 ed and continued to  the end of  the program with no problems of any kind.
 Due to the  fact that this was a last minute change under a demonstration
 grant extension,  little additional data was obtained.   However, it has
 demonstrated conclusively that the highly agitated glue factory effluent,
 with its extremely high concentration of entrained air  bubbles of
 'resonant' size,  was solely responsible for the poor performance at the
 South Shore Site  since the sewage volume passing the College Avenue probes
 is the very same  as that passing the  South  Shore probes with the solitary
exception of the  glue factory effluent.
                                  59

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                               SECTION VI

                          DISCUSSION OF RESULTS

ALLOWABLE SOLIDS LOADING & AIR ENTRAINMENT
Although existing instrumentation was applied in the demonstration for
both the ultrasonic velocity and level measurements, modifications were
required to suit it to the wastewater metering application.  In the case
of the velocity measurement, adequate pulse propagation in the presence
of varying entrainments of suspended solids and air bubbles required
added sophistication in the detection circuitry.  Automatic gain control
(AGC) was added to provide uniform detected signal amplitudes under con-
ditions of changing received pulse energies.  Even with AGC, use of
leading edge pulse detection resulted in unacceptably large errors in
the velocity measurement.  So pulse peak detection was used instead by
detecting the received pulse envelope, differentiating, and triggering
on the zero crossing of the derivative.

Infrequent passage of large solids can be expected to  (and did) complete-
ly block the transmission of occasional ultrasonic pulses, introducing
another error into the velocity determination.  This problem was minim-
ized by automatic insertion of an external trigger pulse substituting
for the missed pulse.  The results of these modifications to the de-
tection and signal processing circuitry made it possible to measure waste-
water velocity accurately within the following figure of merit (Lead-
Length Product, or LLP) relating the conduit diameter and solids loading:

                          (D)  x (SS)  <_ 5000

where D is sewer diameter in meters and SS is the suspended solids con-
                                    60

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 centration in milligrams per liter.

 Solids loadings in the Cambridge Avenue and College Avenue sewers were
 in the range of 200 milligrams per liter, well below limiting values of
 3300 and 1380 milligrams per liter respectively, so no difficulties due
 to solids loadings were encountered.  In full pipe installations in
 Japan (see Appendix D)  successful flow measurements are also being made
 on return sludge with solids loadings of 10,000 milligrams per liter in
 a 0.2 meter line.   So for the typical conduit diameters presented in the
 following table no operational limitations would be expected for suspended
 solids loadings which did not exceed the maximum level specified:

                                                Maximum
             Conduit Diameter                Suspended  Solids
           _	(meters)	       Concentration milligrams per liter
                   -2                          25,000
                   -3                          16,700
                   -6                           8,300
                   1-                           5,000
                   i-5                           3,300
                   2                              2,500
                   3                              1,700
                   5                              1,000

Entrained air bubbles caused operational problems at the South Shore
installation site because of dissipation of the  ultrasonic pulse due to
scattering by the resonant entrained air bubbles.  In this installation,
20 to 50% of the sewage flow was due to a single effluent reaching the
sewer from a glue factory at a point about 10 minutes upstream from the
meter site.  Air bubbles are generated in this effluent because it
enters the main sewer via a 58.7-foot vertical drop (see Figure 11).
Bubble lifetime in wastewater is longer than in tap water bacause of
bubble adherence to solids particles.  There were still enough bubbles
in the sewage after a 10 minute transit time to completely occlude the
                                   61

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ultrasonic transmission.  Accordingly, another criterion for meter instal-
lation sites is to "avoid waterfalls".  In other words, select probe sites
which are reasonably free of severe upstream agitation.  Normal sewer
flows are sufficiently quiescent so as to avoid excessive air entrainment.
No entrained air difficulties were encountered at the Cambridge Avenue or
College Avenue installations.

LEVEL GAUGE INSTALLATION CRITERION
We experienced some temporary difficulties with level gauge performance
at the College Avenue Site due to standing ripples in the sewage surface
which interfered with echo returns.  This was alleviated by moving the
level sensor a few feet to a point where the sewage surface was less dis-
turbed, with only random surface turbulence.  Inaccuracy due to occasional
missed echos was satisfactorily minimized by electronic damping.

PROBE FOULING BY DEBRIS & GREASE
One of the major design features which was a subject of considerable
conjecture before the installations were made was the possible suscep-
tibility to fouling of the velocity probes by passing debris and grease.
A major result of the program was the demonstration that this did not in
fact occur, arid the meters,  once operational, remained in service without
further attention at least for the duration of the demonstration (18
months for the Cambridge Avenue meter) and probably indefinitely.  The
velocity probes at the South Shore Site were inspected about a year after
installation,  and a quarter inch deposit on the probe face was noted.
However,  the systems continue to operate properly even though the sound
pulses must first propagate through the deposited layer.  The thickness
of the deposits is apparently limited due to a balance between deposition
rate and erosion rate.   In other words, thicker deposits are eroded by
the abrasion of passing solids,  and thus build only to tolerable thick-
nesses.  The protective housings surrounding the probes were designed
to prevent the accumulation of rags,  branches or other debris, and per-
formed successfully.   Materials used must be tough and noncorrodible,
                                    62

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  stainless steel  or  plastic.

  VELOCITY  PROFILES & PROBE MULTIPLICITY
  Another major design feature to be demonstrated was the ability to measure
  flow accurately  with the use of only a single probe set for the velocity
  measurement, and a  single level transducer.  To accomplish this, a usable
  relationship between area velocity v& and chordal velocity v  had to be
  derived and applied.  Using extensive flow profile data collected by
  Barnes4 and Nikuradse5, the analysis of Appendix A demonstrates that in
  subcritical open channel flow,  v& and VG are sufficiently close to being
  linearly related to enable flow to be measured within 2% over a range of
 depths from 35% full to full,  using just a single velocity probe set
 mounted below the 35% level,  and a single level transducer.   Because of
 the complexity of solution for  the Navier-Stokes equations for turbulent
 flow,  an attempt was made to  infer turbulent velpcity provile information
 from laminar flow data  for various channel shapes.   For circular channels
 running full or  partially filled,  an  apparent 6th power relationship was
 observed between normalized laminar chordal  velocities and normalized
 turbulent chordal velocities.   For rectangular  channels, the  relationship
 appears to be 4th power.   The utility of  these  relationships  is  the  ease
 with which average chordal velocities in  turbulent flow can be obtained,
 as  well as the subsequent  computations of  v^v^  the k-factor, provides
 a measure  of  the  accuracy of flow  measurement based on an  area velocity
 inferred from a single chordal  velocity.

After the  necessary  electronic modifications were made  for the wastewater
application, and  the South Shore test site was abandoned in favor of the
College Avenue Site to avoid the air bubble problem,  all equipment per-
formed satisfactorily.  Ultrasonic flow measurements checked well with
current meter traversals at Jones Island (2%), and reasonably well with
the transient mag meter readings at the South Shore Site.  All equipment
remained in operation at the close of  the demonstration project.
                                    63

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EQUIPMENT COSTS
At the time of the demonstration program, equipment costs were approximate-
ly $12,200 for the ultrasonic velocity meter, $1,200 for the ultrasonic
level gauge and about $1,600 for the mounting fixtures, cables and electri-
cal conduits.  Total system cost for each site was thus about $15,000
(this included multiple velocity probe sets).  Current costs are sig-
nificantly less, being approximately $7,500  for the ultrasonic velocity
meter, $1,000 for the ultrasonic level gauge, and $1,000 for mounting
fixtures, cables and electrical conduits, for a total system cost of
about $9,500 for each site (with a single velocity probe set).

For the large diameters metered (51 and 12'), this cost compares well
with that of other flow metering devices such as venturi and magnetic
meters which require full pipes for operation.  It is relatively more
expensive than flumes or weirs.  However, the ultrasonic system continues
to measure accurately when the sewer is surcharged,  when weirs and flumes
become inoperative.  Further simplifications of the ultrasonic circuitry
made possible through more extensive use  of integrated circuits have the
promise of further reducing the $9,500 system cost.
                                    64

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                                SECTION VII
                                REFERENCES
 1.    Genthe, W. K., and Yamamoto, M., "A New Ultrasonic Flowmeter for
       Flows in Large Conduits and Open Channels", Proceedings of the
       Symposium on Flow, AIP, ASME, ISA, NBS, Pittsburgh, Pennsylvania,
       May 10-14 (1971).


 2.    Birger,  G. I.,  "Certain Problems in Calibrating Ultrasonic Flow-
       meters",  Measurement Techniques,  Vol.  10,  pp.  872-874, October (1962)

 3.    Yamamoto,  M.,  Tokyo Keiki Co.,  Ltd.,  Tokyo,  Japan.   Private
       Communication,  1969.


 4.     Barnes, A. H.,  "Velocity Distribution  Factors  in a  Circular Cross-
       Section",  u. S. Bureau  of Public  Roads Contract #CPR-ll-3584,
       Colorado State  University Engineering  Research Center,  October  (1966),

 5.     Nikuradse, J.,  "Untersuchung Uber Die  Geschwindigkeitsverteilung  in
       Turbulenten Stromungen"   (1926)


6.    Landau, L. D., and Lifschitz, E. M., Fluid Mechanics. Pergamon,
      London, p. 120  (1959).


7.    Henderson,  F. M.,  Open Channel Flow. Macmillan, New York (1970),
      522 pgs.
                                     65

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                         SECTION VIII

                          APPENDICES
                                                     Page No.
A.   Velocity Profile Analysis	 67

B.   Computer Program for Solution of the Navier-
     Stokes Equations for Laminar Flow in a
     Rectangular Open Channel	 89

C.   Derivation Relating Laminar Chordal Velocity
     and the 6th Power of Turbulent Chordal Velocity.. 93

D.   Summary of Ultrasonic Wastewater Metering
     Performance in Installation in Japan	 93
                               66

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                                APPENDIX A

                         VELOCITY PROFILE ANALYSIS

 Concurrently with the demonstration of the metering equipment, an investi-
 gation of velocity profiles was undertaken.  This included an examination
 of much data for various conduit geometries and another look at the theo-
 retical characterization of turbulent flow.  The primary objective of the
 investigation was to obtain the relationship between the average velocity
 in a horizontal plane or chord (VG),  the level of that plane or chord ()
 and the average velocity over the entire flow cross section (v ).   Although
 it was not anticipated as a probable  result of the analysis,  a means of
 predicting the relationships between  v^  v&/  and  by a computer program
 would have been desirable and was included as a secondary objective.

 Experimental  k-factor analysis
 Having ultrasonically measured the average chordal  velocity v   at  a  chord
 level  ,  it is  necessary to  relate this  to the  average  area velocity  v
 This  relationship can be mathematically  stated  as:

                    v  (t)   =   k(,v  )v  U;t)
                      a              C  C

 where  k is  the proportionality  factor which is a function of both the level
 at which VG is determined and the value of the average chordal velocity
 itself.  In addition, the k-factor would be expected to vary in its
 functional dependence on  and VQ with variations in conduit geometry.

At first glance such  functional dependence and interdependences would
appear to present an  insurmountable barrier to successful analysis;
however, it was found that there were  several saving factors.
                                    67

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 Limiting  the  analysis  to  turbulent  flow,  it  became  evident  upon
 examining existing  data from a  variety  of sources that  the  value  of
 k  is  nearly independent of both level and average chordal velocity over
 a  major portion  of  the depth.   Furthermore,  it  appears  to be  relatively
 independent of conduit geometry.  This  is reasonable when one considers
 the natural asymptote  of  the process.   In extreme turbulence  it would
 be expected that over  a major portion of  the cross  section  the average
 chordal velocity, would be nearly equal to the  average  area velocity,
 i.e.,  k = 1.

 Although  the  Russians  and Japanese  have published some  results of
 studies of the k-factor,  relatively little work has been done.  The
 difficulty is principally that  of obtaining  reliable data in  large
 conduits  during  well-developed  turbulent  flow.  Fortunately a great
 deal  of reliable data  was found to  have been obtained during  an unrelated
 study by  Professor  A.  H.  Barnes at  Colorado  State University.  The
 apparatus used consisted  of  an  800  ft.  long/3 ft. diameter  conduit.  It
 was supplied by  a reservoir  with a  200  ft. head and had the capability
 of variable slope.  The velocity data was  obtained using propeller meters
 mounted on rods  which  could  be  rotated  in  a  plane perpendicular to the
 conduit axis.  From this  data cross-sectional plots of  isovels were
 obtained  for several depths  and flows.  These isovel plots  were then
 used  to obtain velocity profiles in horizontal  planes at various levels.
 Integrating these profiles and  averaging over the chord length and
 dividing the resulting value of v   into the  average area velocity, v
                                 C                                  cl
 determined the value of k at that level.   In this manner a  plot of k as
 a function of level was obtained for that particular flow situation.  In
 each case, a computer generated set of k values for laminar flow in a
pipe  filled to the  same depth was obtained.  Isovel diagrams  for pipes
 roughly one third and two thirds full as well as for a  full pipe are
 shown  in Figures  35, 36 and  37 respectively,  along with the k-factor
plots  for each.
                                   68

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  In  addition  to  the  circular  conduits,  an  isovel  diagram of  a
  partially  full  rectangular conduit, obtained  and published  by
  Nikuradse, was  analyzed  and  the k-factors obtained.  Again, a com-
  puter generated k-factor for laminar flow in  a similar  conduit
  at  a similar depth was obtained.  This is presented as  Figure 15.
  In  an effort to independently ascertain the value of the k-factor
  for a typical sewer channel, a readily accessible open  rectangular
  channel at the  Milwaukee Sewerage Commission's Jones Island Treat-
 ment Plant was  studied.  This channel connects the coarse-screen
 house and grit  chamber area,  is 10 feet wide and 8.5 feet deep.   A
 Gemware magnetic type current meter of the type shown in Figure 39
 was utilized in the study.  Data was obtained over approximately a
 two hour period from 1300 to 1500 hours on September 28, 1972.
 During the  test period the level remained at 7.06 feet with fluctu-
 ations of less than 1%.  During the same period the ultrasonic
 velocity meter had an average indication of  4.5 ft/sec with fluctu-
 ations of  6%.   Current  meter readings were taken at one foot
 vertical intervals along  the  vertical  center line,  and verticals
 2.5,  4.0 and  4.5 feet from that center  line.   A plot of this data is
 presented as  Figure  40.   A horizontal profile  at  the 2.5 foot level
 (the level  at which  the ultrasonic  velocity  probes  are  located)  re-
 flecting the  values  taken over the  same averaging period is  shown
 in Figure 41.  Interpolation  and integration yield  a chordal average
 velocity of 4.475  ft./sec.  This value  calculated from  the profiles
 measured with the  current meter agrees  closely with  the  average  re-
 corded value  from  the ultrasonic velocimeter of 4.5  ftyfeec.  Without
 doubt, the error is less  than the inherent measurement errors en-
 countered during the test and may not be entirely accurate itself;
 however, it would be expected to be of that approximate  percentage.

An estimation of the average  area velocity, based on the profiles in
Figure 42 of 4.29 ft./sec. indicates that the chordal average velocity
                                  69

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  Figure 40.  Vertical Velocity Profiles,  Jones Island Influent Channel.
Figure 41.  Horizontal Velocity Profile, Jones Island Influent Channel.
                                    75

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value of 4.475 feet per second is approximately equal to 0.96 times the
area average velocity,  i.e.,  a k-factor of 0.96.  This is in close
agreement with values for other open rectangular channels reported by
others.  Unfortunately the above experiment could not be repeated at any
of the sites covered by this demonstration grant due to their location.

Having obtained k-factor plots versus depth for circular conduits filled
to various levels, and in turbulent flow,  a composite plot of k-factor
versus proportion of depth (0 - bottom, 1.0 = surface) for circular
conduits filled to a depth of 0.77R, 1.61R and 2.OR (full) was made (see
Figure 42).   This family of curves is also presented as a plot of
k-factor versus liquid level (0 = empty, 2.OR = full)  as Figure 20.
Finally, from this last family, a family of curves (Figure 44) represent-
ing the k-factor versus liquid level as the probe chord level is varied
was obtained.  Although it would have been desirable to have had more
data sets, there is a sufficient density of data to indicate the general
trend, i.e., that velocity probes situated to measure the average velocity
along the chord at a depth of 0.7R  (35% of maximum) would have measured
an average chordal velocity which was within 1% or 2% of the average area
velocity for all flow levels between 0.7R and 2.0% (full).  Some sacri-
fice in the constancy of the k-factor for level fluctuations would be
experienced if the probes were situated at a depth less than 0.7R.  (Note
that as probe placement level and level of flow jointly approach O.OR,
the k-factor must asymptotically approach infinity.)

In essence,  this means that by their judicious placement, a single
ultrasonic velocity probe set allows sufficiently accurate (1% or 2%)
measurement of the average area velocity for a wide range of levels
provided that turbulent flow conditions exist.  This is a result of the
relative constancy of the k-factor over a wide range of depths.
                                    76

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                    Figure 42.  k-Factor Versus Proportion of Depth.
                    Figure  43.   k-Factor Versus Liquid Level
Figure 44.  k-Factor Versus Liquid Level for Various Probe Chord Levels.
                                     77

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Computer Aided Theoretical Analysis
A computer program was developed to present the axial velocities
at cross-sectional area grid intersections for irregular shaped
conduits with vertical symmetry in laminar flow.  The computer pro-
gram interatively solves the Navier-Stokes equation for laminar
incompressible flow given as

                     2
                    V v  + k = 0

where v is the axial velocity, k is the product of the gravitational
acceleration (g) and the slope (s) divided by the kinemetic viscosity
(v).  The boundary conditions are v = 0 at the walls and, in the
                         8v
case of an open channel, -r = 0 at the surface (where h is the
                         dh
coordinate perpendicular to the surface).  (The program, for an open
rectangular channel, is presented in Appendix B.)

In attempting to solve this equation for either full or open (partially
filled) circular channels, some thought was given to an appropriate
coordinate system.  The cylindrical system is the obvious choice for
the full circular channel, however, it presents a number of problems
when used for an open circular channel, not the least of which is the
implementation of the surface boundary condition.   Additional problems
are encountered in maintaining a more-or-less uniform grid throughout
the cross section.  It appeared that the bi-polar (or bi-cylindrical)
coordinate system might be a better choice.  And,  indeed it did
facilitate the application of the surface boundary condition but made
the wall-surface boundary difficult to define.  Furthermore, determin-
ation of the lengths of the grid segments (needed for the interative
technique used in solving Poisson's equation)  would have required
either a prohibitively large number of grid points or an integration
subroutine for each segment.  A few trial runs proved that inadequate
data accuracy resulted when a grid of reasonable size was selected and
the segment lengths were approximated using standard techniques.
                                    78

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 In view of the above difficulties, the cartesian system was again con-
 sidered and found to have several features previously not appreciated;
 i.e.,  grid patterns are rectilinear (not curvilinear!),  segment lengths
 are uniform in any given row or column (except for the last segment in
 a row or column)  and the segment lengths are not a function of the
 coordinates (except at boundaries), data can be easily plotted and other-
 wise manipulated  and boundaries for various shapes (not just rectangular
 or circular)  can  usually be easily specified mathematically.   This last
 feature is of further significance when future solutions for channels
 with trapezoidal,  flat-side circular and other mixed  geometries are con-
 sidered.   Hence,  a computer program was written which uses  a rectilinear
 grid size that can also be  varied within the cross section,  if desired.

 A trial solution  for a full circular channel was obtained (using theo-
 retically predicted values).  Accuracy  beyond the third  place  was obtained,
 and  is  deemed  sufficient  for the  present  purposes.  Other trial  solutions
 for  full  rectangular channels indicate  the  same,  or better,  accuracy
 when compared  to  experimental results obtained  by others  (notably
 Leutheusser).

 The  output consists  of  the  velocity  at  each  grid  intersection point
 normalized to  the velocity  at the  intersection of  the  surface and  the
 vertical  centerline.   (Geometries  not having  symmetry about the vertical
 axis are  not presently being considered.)

 Inasmuch as the Navier-Stokes equation describing turbulent flow becomes
 far  too complex for computer solutions on any but the largest computer
 systems, efforts were directed at correlating the laminar and turbulent
data.  The results, although incomplete, are encouraging and a corre-
lation of sorts does appear to exist.  This is discussed later.
                                    79

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Full Circular  Channel Analysis
As  indicated above,  the velocity profile  for  the  full  circular
channel  in  the laminar region obtained by the computer agreed with
that predicated on the theory.  This  distribution was  compared  to
the data obtained by Nikuradse  for  the full circular channel in
the turbulent  region.  The velocities along each  chord were
normalized  to  the velocity at the centerline  of the chord  for both
the laminar and turbulent cases.  This data was plotted versus  the
fraction of the distance along  the  chord  from the centerline to
the wall.   As  shown  in Figure 45, the theoretical and  experimental
laminar  data correlate exactly  for  all chords, and the experimental
turbulent data correlates quite well  for  all  chords considering
the inherent errors  involved in extracting data from the small
figure in the  Nikuradse paper.  The fact  that the normalized laminar
chordal  velocity distributions  are  identical  for  any normalized chord
can be easily  shown.

Referring to Figure  46, note that for the  observed data to lie  on the
same line it would be necessary that the following relationship  be
valid.
Indeed, substitution of L/L  for r in the theoretically derived
equation for a full circular channel in the laminar region:
       2
v = 1-r  (with R and v    both unity) and the trigonometric formula for
                      max
                             22        22          ?
a right triangle from which L  = r  - (1-d)  and L  = l-(l-d)  shows
                                                  c
that the relationship does indeed hold,  as expected.
Further study of the chordal velocity distributions for the full cir-
cular channel in the turbulent region, as given in Figure 45, seems to
                                   80

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                                                      a
                                                      u
                                                       U
                                                       n
                                                      H
                                                      U
                                                       o
                                                      H
                                                      -p
                                                       (D
                                                      J
                                                      in

                                                      
-------
indicate that a similar relationship may exist for the turbulent case; if
not exactly, then possibly it would be close enough to assume as exact in
any approximation.  Several attempts to approximate the distribution are
shown in Figure 45, including that of Nikuradse  (v   = r/R)
ever, that the equation
                                                              Note how-
                        VL  =Vt
                          n     n
yields a much closer fit.
Figure 47 is a plot of the normalized turbulent velocities versus the
normalized laminar velocities at
the 6th power relationship fits.
normalized laminar velocities at the same L/L  ratio.  Note how closely
                                             V*f
It would appear that this approximation might provide a good transfor-
mation relationship for converting the laminar data to turbulent values
for this example.
               Figure 46.   Circular Channel Geometry
                                   82

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                                             r-
                                             ^

                                              o>
83

-------
Open Circular Channel Analysis
Using the computer program at hand, a normalized laminar velocity profile
was obtained for an open circular channel of unit radius and filled to a
depth of 0.766 times the radius.  This was then compared, in a manner
similar to that described for the full channel, with a profile presented
by Barnes (Figure 48) of a similar circular channel in turbulent flow.
The Barnes profile was then sectioned in such a fashion as to match the
computer solution grid for the laminar case.  The theoretical or experi-
mental laminar normalized chordal velocities (Figure 49) again fall on
essentially the same curve for all chords, with some deviations caused
most probably by computer iteration errors near the boundary (since all
deviations of any amount occur near L/L  or for the bottom row or two
                                       C*
of the grid).  In addition, the experimental turbulent distributions
indicate a strong correlation with each other for all chords (again some
values for L/LC > 0.8 and for the surface grid and bottom grid are
questionable inasmuch as they were obtained through interpolation from
graphical representations of the raw chordal data).  Also, note the good
correlation of the turbulent data to the 6th root of the laminar data
for any given L/L  value.
                 c

The plot of v  versus v , obtained using the plots given in Figure 49,
             L         Li
is presented in Figure 50.  It appears that the same relationship holds
here as for the full circular channel.  There is, however, one major
difference which is not immediately evident, and this is the marked
difference in the vertical profiles.  One possible saving characteristic
is noted and that is that the vertical profiles, when appropriately
normalized,  do seem to correlate well.

The apparent correlation between the normalized laminar chordal velocities
and the 6th power of the normalized turbulent chordal velocities would
not at first appear to have any theoretical justification.  However, if
one considers the viscosity to be a function of velocity, then such a
                                    84

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                         O O   UI  IA
                         UI UI   CO   O
                         O.CO   U.

                           ui   .4-
                                S<*\   en
                         _
              CM I         .   I     |
              -
            K  UI>-OC 
            i
                                              H
                                              P
                                              to
rbulent
                                to

                                &

                                en
                                rH
                                0)


                                I
                                H
                                              00
U>
H
b
85

-------
                        NO
O

OH
                                                                                                                     O
                                                                                                                     U-l

                                                                                                                      rH
                                                                                                                        H
                                                                                                                     H -H
                                                                                                                      Q)  +J

                                                           86

-------
 direct  correlation  is not only  theoretically possible  (see the derivation
 in Appendix B) but  practically  probable.  The concept of expressing the
 viscosity of a turbulent fluid  by a value different than that used when
 it is in laminar flow is discussed by Landau and Lifshitz.  However, there
 remain  two unresolved problems.  First, the way in which the power in
 the relationship is determined  is not known.  For instance, under similar
 flow conditions the relationship between the normalized laminar velocities
 and the normalized turbulent velocities for the open rectangular channel
 appears to be fourth order, i.d. VL  * vt4.  Second, the depression of
                                   n     n
 the maximum flow velocities to levels below the surface are not explained
 by such a correlation.  Generally,  this depression is attributed to
 secondary flows.   However,  there appears to be some validity in attaining
 the same result by the use of proper surface boundary conditions.  Such
an approach is briefly alluded to by Henderson.   Unfortunately,  the
continuation of this theoretical investigation is beyond the scope of
this demonstration,  although it would seem to be a worthwhile pursuit.
                                   87

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 vO
                           OC


                           <
                                                   1,
                                                    00
                                                   4- 

                                                     o
00
  

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-------
                           APPENDIX B

                 COMPUTER PROGRAM FOR SOLUTION
                             OF THE
                    NAVIER-STOKES EQUATIONS
                               FOR
           LAMINAR FLOW IN A RECTANGULAR OPEN CHANNEL
 A computer program which iteratively solves the Poisson equation
                      2
                     V v + k  =  0

 is presented.   A cartesian coordinate system is used with a maximum
 grid size of 10 x 10, not including the wall boundaries (bottom and
 side).   As shown,  the program will find the laminar velocities at
 grid intersection points normalized to the velocity value at the
 center  of the  surface.   Symmetry about the vertical centerline is
 assumed.   The  boundary condition at the surface is
                                 0
                           surface

For geometries having proper symmetry but irregular sides and/or
bottom, it is necessary to modify the portions labelled:  Initial
Data, Row and Column Lengths and Number and Length of Each Row
and Column Segment.  This can be done as a data entry or by another
computer program.

Output data is presented in matrix form with the average row velocity
presented first for each row, followed by the centerline velocity and
thence each velocity sequentially to the wall.  Vertically rows are
presented from the surface down to the bottom.  The average velocity
over the entire area is presented as a single-entry final row.

                                 89

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        RECTANGULAR-OPEN
   DIMENSION RL(1Q),CL(10),NSEUR(10),NSEGC(10>
   DIMENSION RSEGL(10.10),CSEGL(io,10),C(10,lO,5),V(ll,ll>
   DIMENSION VH(10lO)tVC(10)
 1 FORMAT(1X,F6.3,4X,10F6.3)
 2 FORMAT(1X,F6.3)
 3 FORMAT(F6.3)
        INITIAL  DATA
   READ(5,2)DLR
   READ(5,2)DLC

   NC=10
   A = 0.0
   8=1.0
   EPS=1.0E-10
   DO 5 1=1,11
   DO 5 J=l,ll
 5 V(I,J)=0.0
   CK=400.0
        ROk AND  COLUMN LENGTHS
   RI=NC
   DR=RIDLR
   RJ = NR
   DC=RJDLC
   DO 10 1=1,NR
10 RL(I)=DR
   DO 15 J=1,NC
15 CL(J) = DC
        NUMBER AND LENGTH OF bACH ROW AND COLUMN SEGMENT
   DO 25 1=1,NR
   SEGN = RL( D/DLR
   ISEGN=SEGN
   TSEGN=ISEGN
   K=l
   IFSEGN-TSEGN),LT.0.001) K=Q
   NSEGR(I)=ISEGN+K
   DO 20 J=l,ISEGN
20 RSEGL(IJ)DLR
25 IF(K.EO,1) RSEGLU'ISEGNM > = DLR (SEGN-TSEGN )
   DO 35 J=1,NC
   SEGN=CL(J)/DLC
   ISEGN=SEGN
   TSEGN=ISEGN
   K = l
   IF((SEGN-TSEGN).LT .0.001) K=0
   NSEGC(J)=ISEGN*K
   DO 30 1=1,ISEGN
30 CSEGL( I  ,J)DLC
35 IF(K.EQ.l) CSEGL(ISEGN*1,J>=DLC(SEGN-TSEGN)
                           90

-------
         GRID  INTERSECTION
    C(l,l.l)=A/(CSEGLCSEGL<1.1
    C(1,1,4)=C<1.1,2)
    C(1.1.5)=C(l.l,l)*C(l.l,2)*C(i,i.3)
    NT=NSEGC(1)
    DO  40  1=2, NT
    C( I,1,1)=2.0/(CSEGL< I-1.1>=C
    DO  42  J=2,NT
    C(l, J1>=A/(CSEGL<1, J)CSEGL(i,j))
    C(l. J.2)s2iO/
    DO  44  J=2,NT
    C( I, J,D=2.0/(CSEGL( 1-1. J)< CSEGK I , J) *CSEGL ( I -1 , J ) ) )
    C(I,J,2)=2.0/(RSEGL )
    C(I,J,4)*2.0/(RSEGL(I,J)*(SEGL(I, J)*RSEGL( I . J-l ) ) )
 44  C(!,J,5)=C+C
        GRID  INTERSECTION VELOCITIES
 48  T = V(1, 1)
    V(1,1)=((C(1,1,1)*C(1,1,3))*V(2,1)
  1       *(C(1.1,2)*C(1.1.4))*V(1.2)*CK)/C(1,1.5)
    NT=NSEGC(1)
    DO  50  1=2, NT
 50  V+C< I, J,3)V
-------
        OUTPUT

62
   DO 70 1=1, NR
   NT=NSEGR(I )
   RNT=NT
   SUMP = SUMP-RNT
   SUMBsQ
   DO 75 K=1,NT
75 SUMB=SUMB+V< I
   AVGB=SUMB/RNT
   VC(I )=AVGB
70 WRITE (3.1) AVGB, ( V ( I , J ) , J=l. NT )
   AVGA=SUMA/SUMP
   WRITE (3,2) AVGA
   DO 72 1=1, NR
   VK = AVGA/VC(I )
72 WRITE(3,2)VK
   STOP
   END
                           92

-------
                          APPENDIX C
         DERIVATION RELATING LAMINAR CHORDAL VELOCITY
                           AND THE
           6TH  POWER OF  TURBULENT CHORDAL VELOCITY
                                  Af   + M   Centered at (XQ,  YQ/  ZQ)

                                     0        having sides Ax,  Ay,  Az

                                              and viscosity v
                      t\
Assume that n = nQ +  ^ Aw and v = -^ with uniform p, then  the


shear forces are
     Af    +
     Af
                    n_ -

                          9n
Ay
 2
it
                     o    By
Ay;
 2
                                      8v
                                           o   8y'

                                                2
             3 Vx
                                            o  3y'
Ay AxAz
 2J
The difference in shear forces is Af =
     Af =
                2
               9 v
            o    2
                           v    I 8y
                            x   *-
                                          AxAyAz
                               93

-------
 The term
           1  lim  Af .
             A -K> Av is the acceleration term due to viscosity




effects (AV = AxAyAz),  and since n= pv=>
           xy
2
8 v
x 8v
2 ' 8v
a x
8v
x
3y
 Including  the  similar term for trie z direction shears,  yields
           V    =  V

           X
                    8  v      8  v
                                              8v
                                                           8v
                                                           8z
For the assumption  that  v   ^  v   (x),  this can be rewritten as
         .
         v    = vV  v  + 
          x        x    8V
                                 (V'Vv  )
                                     x
Assuming that the viscosity  can be  expressed  in  terms  of powers
of v  , i.e.
    x
         V = V V
              O X
                 n-1
then
         a      o    _2  n
          v  = 	   V v
           x    n       x
Assuming gravitational flow, the modified Navier-Stokes equation


would be
         V2v
            x       v
                            = 0
                                 94

-------
where  g  is  the  gravitational  constant and oc  is the angle of


inclination.  Note  that  the laminar  solution  is given when n = 1.





The  solution  at the surface,  where the equation would be  given as
    A2  n
    d v
       x	                    ng  sin**
        + k =  0  with  k  = 	 ,
     dy                          vo
                    follows.
Assume a width w and v  =  0  at  y =  0  and  y = w.  Then
                      X
       n    k   2

     Vx  + "2 Y + C1Y + C2 =  -
Since v  = 0 at y = 0,   C  =  0 and evaluation  at y = w yields,
       x                  &

       j^

C, = -  w.  Thus





        n    k    /
      vx  =  y  (w-y)




                                 w
Normalizing v  to v     and y  to  yields
             XX             ^
                    max
       v n = y(2-y)   with  v              sin
        x                    x          8
                              max        v
                                          o
 (Note that to be dimensionally correct v = v  v   has an implied
                                            ox           r

unit coefficient whose dimension is  (sec/ )n.)
                                         m
Hence



                          1/n
        v
         X
          turb
                   V
                    x
lam
This appears to work well for normalized horizontal cross sections of


both circular and rectangular channels running full or open.
                                 95

-------
 Air-Water Boundary Conditions
                 \
                 I
            AIR  [  \
                I   v
        	[
           WATER   \
        .  Az
        + ~T
      o    2
                                  interface plane
                              *- "z
                                     o     2
The shear at the upper  surface  is
     Af     Az
 .
air
                     air
Az
               X  .
                air
                                                         32v
         x .
          air
                                                                   o
                                     _A_z
                                      2
                                                                        AxAy
and at the bottom
     Af     Az
       Zo ' -1
                    water
water
  9z
           Az_
            2
 water        water)  Az
9z      "        2  |   2
       1 o      9z    o
                                    AxAy
Equating the two in the limit as z o yields
         1 .        air    rj            water
         air    __	 _  water	    (at the  surface)
                                     96

-------
Assuming that the velocities at the interface are the  same yields


the condition that
           v       v
            x .   =  x           (at the surface)
             air     water
                                97

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                                APPENDIX  D

                     SUMMARY OF ULTRASONIC WASTEWATER
                           METERING PERFORMANCE
                          INSTALLATIONS IN JAPAN
 During the sewage metering demonstration program conducted in the United
 States, ultrasonic flow measurements were also under way in Japan in
 eleven installations in pipes running full, seven in raw sewage and four
 on return sludge, made by the Tokyo Keiki Company, Ltd.  The following
 table describes the performance of these installations:
              Suspended          Pipe
 Metered        Solids         Diameter
  Liquid    Concentration     and Material
          (Milligrams/liter)  (Millimeters)
 Influent
 Influent     70-100
 Influent
                200
Influent     10,000
Influent     120-130
Influent
                4000
     900
 ductile iron

     800
 ductile iron

    1600
 cast iron,
 rubber  lining
     200
 steel, vinyl
 lining

     700
 steel, poly-
 urethane
 lining

     500
cast iron,
moltar lining
   Approx.
    Flow
(Cubic  Meters
   per  Hour)

    5000
                                                 3000
                                    Remarks
                                               27,000
                                              2m/sec
                                               6000
                                               1000
            Some jitter in
            flow record prob-
            ably due to air
            bubbles from pump
            operation.
            Within 1% of mag
            meter
                                    98

-------
Influent

Return
Sludge
170

10,000-
20,000
600
cast iron
300
steel
Return     4400-9300
Sludge
Return
Sludge

Return
Sludge
   6500
8500-16,000
    300
ductile iron,
cement lining

    300
cast iron

    200
cast iron
                                     4000      Within + 2.1% of
                                               mag meter

                                      700      Large transmission
                                               fluctuations.
                                               Within _2.1% of
                                               mag meter.

                                      500      Within +1.2% of
                                               mag meter.
1200      Difference with
          mag meter - 14%.

 250      Unstable operation
In these installations, the ultrasonic velocimeter probes were attached
to the outside of the pipe wall and sound propagation is through the pipe
wall to the liquid.  Note that plastic, cement or bituminous linings do
not interfere with proper operation.  Tokyo-Keiki has made successful
experimental installations on open channels,  ditches and rivers.  In
these, level was either controlled by constant level gates or measured
with capacitance or float gages.
                                    99

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                                    TECHNICAL REPORT DATA
                             (Please read Instructions on the reverse before completing)
 1. REPORT NO.
  EPA-600/2-76-243
                    3. RECIPIENT'S ACCESSION NO.
 4. TITLE AND SUBTITLE
  "WASTEWATER FLOW MEASUREMENT IN SEWERS USING
   ULTRASOUND"
                    5. REPORT DATE
                     November  1976 (Issuing Date)
                   6. PERFORMING ORGANIZATION CODE
 7. AUTHOR(S)
  R.J. Anderson,  S.S.  Bell, W.H. Vander Heyden,
  W.K. Genthe
                                                           8. PERFORMING ORGANIZATION REPORT NO
 9. PERFORMING ORGANIZATION NAME AND ADDRESS
  Sewerage  Commission
  City of Milwaukee
  Milwaukee, Wisconsin   53201
                    10. PROGRAM ELEMENT NO.

                        1BC611
                    11. CONTRACT/GRANT NO.
                                                               11024 FVQ
 12. SPONSORING AGENCY NAME AND ADDRESS
  Municipal  Environmental Research Labortory
  Office of  Research  and Development
  U.S. Environmental  Protection Agency
  Cincinnati, Ohio     45268	
                    13. TYPE OF REPORT AND PERIOD COVERED
                     Final Rppnri-  4/71  to 9/75
                     . SPONSORING AGENCY CODE
                         EPA - ORD
 15. SUPPLEMENTARY NOTES
  P.O. Clifford Risley,  Jr.
 16. ABSTRACT       ~~                         ~~	~~	
  A new technique  for measurement of sewage volume  flow utilizing ultrasonic
  measurements of  depth  and velocity was demonstrated  and evaluated.  The new
  technique, requiring no  costly construction for installation,  is usable
  for open channel or partially full measurements.   The flow technique can
  accomplish measurement accuracies from 2 to 5% under conditions of rapidly
  changing levels, surcharging, and back-up conditions.   Two installations were
  accomplished on  existing sewers in the Milwaukee  Sewage System, one 12 1/2
  feet and the other 5 feet in diameter.  A continuous flow record was displayed
  for each meter and performance of the meter installations was  compared with
  magnetic flow meters at  one  site and head velocity relations  on the other site.
  Relationship between average volume flow, water level,  and average velocity
  along selected horizontal chords of the sewer cross  section were determined.
  The unit installed on  the 5  foot diameter sewers  operated for  a period in excess
  of  18 months without failure and has required only routine maintenance.  The
  flow technique provides  accurate measurement over a  range of  depths from 25%
  to  full depth in the sewer and from zero to the full flowing velocity of the
  fluid in the sewer.  No  deterioration of ultrasonic  transducer probes has
  been detected indicating  their suitability for use in  the sewer environment.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDED TERMS
                                                                        c.  COS AT I Field/Group
  Flow,  Sewers,  Flowmeters, Combined  Sewers,
  Field  Tests,  Ultrasonic Frequencies,  Flow
  Measurement
       Ultrasound Flowmeter,
       Sewer Environment,
       Ultrasonics
                                                                             13B
 3. DISTRIBUTION STATEMENT

       RELEASE TO PUBLIC
      19. SECURITY CLASS (This Report)
       UNCLASSIFIED
                                              20. SECURITY CLASS (This page)
                                               UNCLASSIFIED
21. NO. OF PAGES
_   110	
22. PRICE
EPA Form 2220-1 (9-73)
Too"
                                                              U. S, GOVERNMENT PRINTING OFFICE: 1978  657-060/1515

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