A design study for a circulating water channel

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r

See note inside cover

SH R 6/62

A Station of the

Department of Scientific and Industrial Research

12th March, 1962

NATIONAL PHYSICAL

LABORATORY

SHIP DIVISION

A DESIGN STUDY FOR A

CIRCULATING WATER CHANNEL

by

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Extracts from this report may be reproduced

provided the source is acknowledged.

Approved on behalf of Director, NPL by

Mr. A. Silverleaf, Superintendent of Ship

Division

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RETURN

CONDUIT

DIFFUSER _UPSTREAM

STILLING

.-SECTION

CONTRACTION

WORKING SECTION

WEIR

SECTION

SUMP

PUMP

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Scale Model

Circuit Stability

Velocity distribution in the working section

Flow conditions with and without an adjustable false floor

Comparison of two types of weir

Pump and sump

Comparison of two splitter type diffusers

Screening in upstream stilling section

Contraction

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A DESIGN STUDY FOR A

CIRCULATING WATER CHANNEL

by

B.N. Steele

Ship Division, National Physical Laboratory

SUMMARY

The flow conditions about a model hull and its propellers are best studied in a circulating water channel. This consists of a channel containing flowing water in which the model hull is placed, the flow being observed through windows in the sides and bottom. The water is made to circulate at any desired speed by means of a pump.

Work has been carried out at the Department of Engineering, Cambridge University, on the flow in a range of water channels, the largest of which had a width of 114 inches and a depth of 11 inches, with the object of

elucidating the factors affecting the production of uniform, wave-free sub-critical flows in water in parallel channels0 A report on this work was written by Orkney in which he included a proposed design of a

circulat-ing water channel for testcirculat-ing model hulls up to 4 ft in length over a range of speed-length ratios having a maximum value of 17O

An extension of Orkneyt s work was carried out by Williams of NFL on the original contraction and channel which Orkney had used, on two NFL

-designed contractions with the same channel, and also on smaller and larger channels at the NFLO These experiments showed that the scaling laws that Orkney had adopted would not enable the higher velocities to be obtained with a level surface in the full-size flume. Consequently, a modified preliminary design for a circulating water channel was prepared by Williams 2 To investigate flow patterns and pressure distributions

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around ship model hulls 8 ft in length, the channel requires a working section at least 12 ft wide and 8 ft deep; the maximum speed of flow

through the working section without stancLing gravity waves should be

about 8 fi/sec, but it is likely that 10 ft/sec may be achieved without

appreciable wave amplitude.

In this design (Fig.1) water is pumped from a sump through a return conduit and a splitter type diffuser to the upstream stilling section. In the stilling section any asymmetry of flow and turbulence is removed by allowing it to pass through a series of screens. The mass of water

then flows through the contraction where it is accelerated to the working section velocity, and downstream of the working section it is allowed to fall over a weir back to the suinp wre, after passing through more screens,

it is recirculated by means of the pump. The novel feature of this design is the installation of the weir fitted to prevent any disturbances created by the pump being transmitted back upstream to the working section, the water passing over the weir falls freely into the sump in which the water

level is below the bottom of the working section, and this is termed a

'free flooded' weir.

In order to investigate fully the characteristics of this circuit, a 1/lOth scale model of the prototype was built at the Ship Hydrodynamics

Laboratory of the NFL, and this report is a summary of the experiments

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I. SCALE MODEL

The circuit shown in Fig.1 was so constructed that each section was completely detachable and could be modified without alteration to the remainder of the circuit; it was thus a simple matter to study a variety of designs for each section. This report deals mainly with those designs which were ultimately found to be satisfactory.

The model had a total length of 30 ft and a width of 6 ft and was

sited in such a position that the quantity of water in the circuit could be changed with no inconvenience to other plant or equipment. The working section was 1.2 ft wide, 1.4 ft deep and 5 ft long, the sides being of

perspex slotted in to a in plywood floor. A horizontal datum surface was provided above this section in the form of machined brass rails. The

weir section had the same dimensions as the working section and was 2 ft

long; it was constructed of in plywood and covered with thin cobex to produce a smooth surface. The cascade weir, which consisted of five brass symmetrical aerofoil sections of approximately 2 in chord, was bolted to the end of the weir section. In order to test various pump and sump combinations, a large galvanised steel tank, 8 ft long

3.7

ft wide and

3.9

ft deep was constructed, and various wooden sump shapes were built up within this shell. The variable speed, adjustable pitch, manganese bronze

impeller was 1 2 in diameter and was fitted with pre-rotation and guide

vanes. This impeller was sited within an accurately machined, i in thick galvanised steel tube which was connected to the 1/8 in thick galvanised

steel return conduit. Three cascaded 900 corners were contained in the return conduit, and at the downstream end a short round to square transition

piece was introduced. In order to make the change from return conduit to stilling section velocity as gradual as possible a splitter type of diffuser

was fitted; this was mde of 1/8 in galvanised steel and was 4 ft long. For simplicity of construction the upstream stilling area was made of wood,

8 ft long, 4 ft wide and

2.5

ft deep, and had a series of slots throughout its length to acccmmodate stilling screens. The shell of the contraction

was .lso of wooden construction, but since frequent modification to the

internal shape was desirable the contraction profile was of paraffin wax which was contained within the wooden shell.

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II. CIRCUIT STABILÏTY

General

Since the initial conception of the present desii of the circulating water channel, there had been concern over the possibility of any inherent

instability, or pendulation, in the circuit which might initiate a periodic movement of the surface of the water passing through the working section.

Consequently SHL consulted the Hydraulics Research Station, Wallingford, and were advised to build a 1/lOth scale model of the whole circuit in order

to study its stability. It was felt by the Hydraulics Research Station that if the model proved stable, the prototype would be satisfactory.

Experiment corH tior.s

Since the type of weir may influence the stability of the circuit, experiments with both a cascade and a tilting weir were performed.

Under normal conditions the weirs were completely free-flooded in operation, but in order to investigate the possibility of operation with the weirs partly flooded, a few experiments were conducted under these conditions.

In all the experiments, measurements of surge over a range of speeds at model working section depths of

_{9", 9-i-"}

and lO" were taken.

Method of measurement

Several methods of measuring the vertical oscillatory movement of the water surface were tried, the most suitable being a capacitance type probe

using a OQOI in diameter wire with shellac as the dielectric, the output

being recorded on a pen recorder. It. was found possible, using this method,

to repeat the calibration very well, this being done in the channel by movement of the probe relative to the still water surface.

Originally it was planned to use 6 probes (i.e. 2 each in the sump,

working section and upstream stilling section). Due to electrical interaction between the probes, however, this was not found to be possible, and it was decided to use only one probe which was placed in the working section at

mid-length and mid-width.

Experiment results

The records of water surface movement were analysed, and the results

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-5-Although it was possible to repeat the probe calibration at various intervals throughout the experiments, it was not possible to repeat the records of the surface movements. This indicates that there is not a urìiue periodic movement associated with each set of operating conditions.

The results given in Tables i to 8 relate to the first experiment conducted

at each condition. The records obtained often displayed a random movement of the water surface, and analysis of the pump revolutions showed that they were fluctuating; it is felt that it was to this that such surface movements

could be attributed. From the pendulation aspect, neither the cascade nor

the tilting weirs showed any difference.

The experiments with both weirs partly flooded indicated that any small sump disturbance will be readily transmitted back upstream to the working

sect.ion, to an amount dependent upon the degree of flooding, the ideal case

being when the weir is completely free-flooded. There is very little

differ-ence between the cascade or the tilting weirs in this respect.

Conclusions

The model experiments suggest that providing the pump speed is maintained very steady and the weir is completely free-flooded, no pendulation should be

experienced on the prototype.

III.

VELOCITY IN THE WORNC- SECTION C-eneral

When the circulating water channel is used for experiments on surface models, the draft of the models will seldom exceed 1/8th of the channel

depth. The velocity near the surface, together with its relation to the velocity at other depths, is therefore of extreme importance. The method of determining this on the 1/lOth scale model, together with the results,

is outlined below.

Experiment conditions

Since the type of weir may influence the velocity distribution, experiments with both a cascade and a tilting weir were undertaken.

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Tables ₉ and. 10 give the model speeds and corresponding prototype speeds

at which the experiments were performed. In all cases the model channel was run at a depth of

9.6

in, corresponding to a prototype depth of 8 ft.

It was not possible to use a miniature current meter for this survey, since experiments have shown such instruments to be unreliable near a solid boundary and in way of the air-water interface. Velocity measirements using small, buoyant particles were found to be more reliable. Since it was

required to take a record of velocity at all depths, it is obvious that free particles at different depths would have to be timed over a fixed length; the

particles used had to be neutrally buoyant and of a relatively small diameter. These particles were made at SRL from the adjoining spheres of a

'1poppit"

necklace coated with a sufficient quantity of lead base paint to make them

neutrally buoyant, and. were approximately 0.1 in in diameter.

The particles were injected into the moving stream by attaching them to an arrangement of hypodermic tubing by means of a thin wax, and gently tapping the hypodermic to release the particles. It is obvious that the particles should all be released in the same vertical plane, but it was not found possible to achieve this, and therefore any experiment in which the spread of particles

exceeded I in was ignored, thus reducing the error to less than 1%.

The passage of the particles through the working section was filmed using a cina camera timed to film at 50 frames/see; the film was then analysed on

the A.R.L. film assessor.

Experiment results

The results of the experiments considered to be the most reliable (i.e.

where the spread of tim particles was the least) are given in Tables 11 and 12. Study of Table 11, at 3Q0 ft/sec, and Table 12, at 1.0 ft/see, indicates that the bottom boundary layer is fairly thick, since a considerable reduction

of speed is evident.

Table 12, at 1.0 ft/eec, shows a very erratic pattern but it is felt that

this Can be attributed to a larger spread of particles than was at the time noted.

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Conclusions

A stuay of Tables 11 and 12 suggests that there is no fall in velocity near the surface, and that it is sensibly uniform throughout the depth

except in way of the bottom boundary layer.

IV. FLOW CONDITIONS WITH AND WIThOUT AN ADJUSTA.BT,F FALSE FLOOR

Ceneral

In order to operate the circulating water channel at various depths, it is necessary to add or remove large quantities of water from the circuit, and it was originally anticipated that this water should be stored in separate large tanks. Ministry of Works engineers suggested, however, that to save expense and simplify the operation of the channel the floor should be capable of

vertical movement, thus providing a means of adjusting the "effective depth" whilst maintaining the volume of water in the circuit constant. The 1/lOth

scale model of the circulating water channel was mofied to investigate this suggestion, and the results of the subsequent experiments are given below.

The false floor was constructed so that it was possible to incline it

through 2° and to vary the "effective depth" between

3.6

and 7 in.

Experiments were conducted to investigate the

following:-Uniformity of velocity in the working section

Velocity traverses at entrance and exit to the working section at corresponding effective depths were made with and without the false

floor over a range of speeds. It was not considered necessary to do this for the maximum depth, since the conditions with and without

the false floor are identical. In the above experiments the false

floor was kept horizontal.

Slope of water surface over length of working section

The inclination of the false floor was varied, and over a range of speeds the fall in level over the length of the working section was

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Stability of circuit with false floor

Measurements of surge were made with the false floor in place in the same manner as described in Section II.

Measurements of velocity were made using a 1 cm diameter miniature current meter, but for reasons already explained it was not possible to make measurements very close to the surface, walls or bottom.

The fall in surface level was measured using a pair of pointer gauges which were zeroed in the channel in the still water condition.

Surge records were taken using the capacitance gauges previously

described.

Experiment Results

Velocity traverses

Study of Figs. 2 to 6 ini cates that with an effective model depth

of

3.6

in (prototype depth of ₃ ft) the flow is very erratic both with and without a false floor, there being very little to choose

between them.

Figs. 7 to 12 show that at t}üs increased model depth of 6.3 in (prototype depth

525

f t) the flow is far more stable, there once

again being very little difference between the flow with or

with-out the false floor.

Surface level

The experiment corditions, together with the results, are shovvn

in Table 13, the accuracy of measurement being approximately ±0.005 in because of surface movements caused by slight

fluc-tuations in pump speed. It was estimated that it should be possible in certain instances to maintain a horizontal water

surface; this was tried and within the limits of accuracy of measurement was found possible.

(c) Circuit stability

It was found that the circuit exhibited no instability with a false floor, except, as noted previously, when changes in pump speed caused slight movements of the water surface.

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Conclusions

It would appear that operation at a low working section depth may lead

to a bad velocity distribution in the working section, both with and. without

the false floor, but at increased depths the velocity distribution should be very reasonable0

There is an indication that inclination of the false floor will enable the water surface to be kept horizontal, but possibly not under all conditions. It is essential that the friction coefficient of the walls be kept as small as

i,

The inclusion of a false floor does not seem to give rise to any circuit

instability.

All the experimental evidence obtained from the model experiments indicates that the installation of a false floor is a feasible proposition,

and if it were not found. to be satisfactory on the prototype it would be

possible to lower the floor and operate the channel as originally intended.

V. COMPARISON OF TWO TYPES OF WEIR

C-e ner al

To prevent disturbances from the pump being transmitted upstream to the working section, it was decided to introduce a break in the circuit

between the working section and the suinp, in the form of a free-flooded

weir. Advice from the Hydraulics Research Staiion indicated that a tilting weir would be the most suitable, but it was suggested by Williams that a cascade weir may overcome some of the disadvantages inherent in a

tilting weir.

Hydrodynamically the three main factors governing the choice of a weir

are:-Stability

Drawdown characteristics

Influence on upstream velocity distribution

It was found from experiments described in Section II that (i) was satisfied with both types of weir, and therefore experiments were performed to

investigate (ii) and (iii).

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Experiment conditions and results

Velocity traverses

In order to effect a comparison between the two weirs, complete velocity traverses were made along the òentreline of the channel

and weir sections. These traverses were made over a range of speeds at a fixed model depth of 9.6", and the results are shown

in Figs. ₁₃ to

16.

Complete traverses were made adjacent to the cascade weir and at the working section exit; these results are

shown in Figs. 17 and 18 respectively.

Drawdown

Measurements of surface level were made at various positions along

the length of the eir section. In the case of the cascade weir it was found that the divergence of the surface from horizontal was of the order of accuracy of the measuring equipment, and the

results are not shown. With the tilting weir, however, the

draw-down was considerable and is shown in Fig. 19 for a range of

speeds.

(o) Fall in surface level over working section

Whilst performing these experiments on the two types of weir, it. was decided to attempt to measure the slope of water surface over

the length of the working section for a range of speeds. Results

of this experiment are given in Fig. 20.

Discussion of Results

(a) Velocity traverses

Figs. ₁₃ to 16 indicate that, as would be expected in the case of

the tilting weir, there is a considerable increase in velocity over

the length of the weir section; with the cascade weir, however,

this effect is almost eliminated. Figs. ₁₃ to 16 also show that with both weirs and at most speeds there is an increase in velocity

of approximately 5% over the lgth of the working section. Fig. 17 shows that there is a variation in speed with depth

adjacent to the cascade weir, but at the working section exit the velocity distribution is quite reasonable.

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(ò) Drawdown

Fig. 19 shows clearly the advantage of the cascade weir over the

tilting weir in this respect; the installation, it will be seen, can result in a substantial saving in length.

(c) Fall in surface level over working section

Fig. 20 shows the fall in level over the length of the working section, and suggests that the tilting weir may be slightly

superior in this respect; te differences, however, are within the limits of accuracy of the measuring equipment.

Conclusions

All evidence from these experiments favour a cascade weir, which would appear to have all the advantages of the tilting weir but none of the

dis-advantages. It would be advisable, however, to allow for the possibility of the installation of a tilting weir on the prototype in case the

apparently favourable characteristics of a cascade weir are not borne out

on a larger scale.

VI. PUMP AND SIThIP

Ceneral

It has been found by Denny that, contrary to expectations, the characteristics cf a sump do not obey the normal scaling laws, and that when using a model geometrically similar to the prototype it is necessary to obtain the same velocity at the pump inlet on both model and prototype in order to investigate the possibility of the formation of air-entraining

vortices. Denny also found that the flow into the pump should be free from any tendency to swirl, and to prevent this, it is desirable to site the pump casing hard against a wall0 For these reasons the sump proposed is as

shown in Fig. 21 Experiments were performed to investigate the air-entraining tendencies of this sump and pump combination0

Experiment Conditions

The maximum normal pump inlet velocity on the prototype is approximately

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was fitted. and the walls of the channel throughout the circuit were raised

another 1 ft. However, the maximum inlet speed which it was found possible to achieve with this arrangement was

755

ft/sec, hence in order to simulate the prototype inlet ccnditions, it was decided to reduce the submergence

diameter

ratio for the model. Experiments were made over a range of

submergence

ratios, the lower values being obtained by reducing the quantity

&iame ter

of water in the circuit.

Discussion of results

It was found that the water flowing over both types of weir entrained considerable quantities of air, and unless the screening arrangements between the weir and pump were very good this entrained air entered the pump inlet and travelled via the return conduit to the upstream stilling section, and

under some conditions was still present in the working section. It was

found possible, by the use of screens of rubberised hair _3" thick and

6 ozs/ft2 in the sump, to prevent this air entrainment almost entirely, and this is shown in Figs. 22 to

30.

There is a strong tendency for the water passing over the weir to flow

in the direction indicated in Fig.

31,

and the velocity of the water in the sump increases with increasing depth. Attempts to explore the flow pattern by means of dye injection were only partially successful, due to turbulence

near the pump inlet.

For each screen arrangement the water level in the surnp was varied, and

the pump run at full power. The surface in each case was carefully studied

for any sign of irregular flow or air-entraining vortices (they were noted.

with some screen arrangements). Table 12 gives details of each condition

run. The system of two screens close together was not tested at lower

submergence ratios than

_2.67,

since it was at once seen that the arrangement of two screens far apart gave better results, the reason being that there was more time for the air passing through screen I to riseto the surface before entering screen 2.

With no screens in place the water surface is very disturbed, and this tends to inhibit the formationof air-entraining vortices. When the screens are in place, they considerably still the surface and remove the air

entrained. at the weir, but a greater tendency to the formation of vortices

does appear. Floating a heavy wooden raft between the last screen and the pump casing may reduce the tendency to vortex formation and also act as a

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The arrangement shown in Fig. 21 appeared. to be satisfactory; final

details of pump entry, however, would be left to the pump manufacturer.

VII. COPARISON OF TNO SPLITTER TYPE DIFFUSERS

Gene rai

The transfer of the water from the sump to the upstream stilling section involves its passage through a 12 ft diameter pipe, at a maximum speed of approximately 7 ft/sec. In an attempt to make the transition from this pipe to the upstream stilling section (where its maximum forward

velocity is I ft/sec) as smooth as possible it was decided to fit a

diffuser, and. in order to keep the angle of diffusion as small as possible

this diffuser is split into several compartments. A design was prepared

at SEL, but because of anticipated. difficulties of construction on the

prototype an alternative design was prepared by MoW, and experiments were carried out to compare these two diffusers.

Velocity traverses with each diffuser in place were made immediately

downstream of the diffuser. The conditions at which these traverses were made are given in Table 15

With each diffuser a set of velocity traverses were made in the working section at a model channel depth of

9.6

in, at speeds given in Table

16.

Experiment results and. Conclusions

The results of velocity traverses immediately downstream of the

diffuser are shown in Figs. 32 and

_33,

and it is seen that the flow is extremely unstable, the fluctuations about a point amounting to as much as

100%. The results given in Figs

32

and

₃₃

are the mean of 8 readings taken

over about

loo

seconds. There would. appear to be a greater asymmetry in

the case of the MoW diffuser. The experiments were terminated at 12 in below the surface, since the flow was seen to be so bad that it was decided

to investigate the effectiveness of the screens (Section

viii)

13

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complete speed range, although the velocity using the MoW diffuser

appears to vary with depth at 1

.5

ft/sec. Any very slight asymmetry which may exist at the exit from the upstream stilling section is

obviously very successfully removed in the contraction. It is emphasised again that very little reliance can be placed on the results close to a boundary, due to the characteristics of the current meter.

VIII. SCREENING- IN TffE UPSTREAM STILLING- SECTION

G-eneral

After passing through the diffuser the flow is very unstable, and it is desirable to rectify this before it enters the contraction. To improve the flow, experiments were conducted to find a suitable screen arrangement. In order to prevent 'bagging' of the scrèens on the prototype, it may be necessary to support them with stiffeners, and therefore model experiments were carried out to assess the influence of these stiffeners on the down-stream velocity distribution.

Experiment conditions and results

Diffuser end of stilling section

It can be seen from Figs. 32 and 33 that the velocity distrib-ution before passing through the screens is not uniform in either width or depth, and experiments were conducted on various screen arrangements in an attempt to improve this. The operation

connUt-ions are as given in Table 15, so that direct comparison of velocity traverses downstream of the screens (Figs. 4-O and 4-1)

may be made with Figs. 32 and

_33.

Downstream of screens

In the outline desi there were 10 screens in the upstream stilling section (4- of 0.5 solidity and 6 of 0.32 solidity), but a velocity traverse just downstream of the last screen indicated

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15

-that although the distribution was vastly better than -that immediately after the diffuser, it was still not good.

Removal of several screens tended to improve the distribution, and it was found that about 4 screens was an optimum number. The velocity distribution was now satisfactory across the width but there was a decrease in velocity with increasing

depth; an attempt was therefore made to grade the solidity of the screens in the vertical direction, the arrangement shown in Fig. )2 finally being considered satisfactory; the

results of velocity traverses with this arrangement are shown

in Figs. 40 and 41.

Experiments to determine the effect of the relative position of the screens tended to confirm the work of Baines and

Petersen4 and Dryden and Schubauer5 in that their relative

pos-itions had little effect provided sufficient space is left

between screens for flow establishment.

(c) Effect of stiffeners

A set of stiffeners of aerofoil section were attached to the last screen of the arrangement shown in Fig. 42, but a vel-ocity traverse did not detect any "shadows" from these struts.

Conclusions

Comparison of Figs. 32, 33, 40 and J-i-1 indicate that regardless

of the flow on entry to the stilling section, it may be improved trem-endously by the careful use of screens. Any small variations in flow remaining at the downstream end of the stilling section are removed in

the contraction.

Experiments to detect any disturbances arising from the thin aero-foil struts proved negative, and it would appear that unless the struts are extremely thick they will have no adverse effects on the flow.

Since it was found possible to obtain a reasonable velocity dis-tribution downstream of the screens on the model scale, it was decided to investigate the effect of increasing the speed to the prototype value.

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It was not possible to do this on the circulating water channel model,

and. therefore a series of experiments were conducted in No.2 towing

tank.

These experiments indicated that provided the nature of the

upstream disturbance is similar, the screens will have the same effect

on the downstream velocity distribution, irrespective of speed.

IX.

CONTRACTION

General

The contraction was designed to give a contraction ratio of 9

: 1

at the design condition of 8 ft channel depth and a channel speed of

8 ft/sec.

There is no exact theory for the design of a free surface

contraction, and the usual method is to assume that the major part of

the flow acceleration takes place in the first third of the contraction

length and that the transition to the working section velocity is very

gradual;

a smooth velocity curve is then drawn and from this the

sec-tion offsets calculated.

This procedure was adopted when designing

the contraction for the circulating water channel, and this was tried

on the model;

it was found, however, that a strong rotary motion was

set up in the contraction.

The contraction was subsequently momti Pied,

and, a sumniary of the experiments performed on this modified contraction

is given herein.

Measurements and observations made

The prmry object of these experiments was to study the flow in

the contraction by the injection of potassium permanganate dye into the

flow through hypodermics.

The screen arrangements in the upstreani

still-ing section were as shown in Fig. 42.

Measurements of the fall in the level of the water surface

through-out the length of the contraction are shown in Fig, 43, where they are

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17

-Experiment results and Conclusions

Table 17 gives the positions at which the dye was injected, and these

conditions are shown in Figs. ₄₄ to 51. Experiments with this contraction and with the original screen arrangement were undertaken, but it was found that due to the reduced velocity at the greater depths there was a cross over of streamlines from the sides to the centre, but these are not shown.

Fig. 45 shows the flow on the bottom of the contraction, and attempts to improve this by the insertion of fillets did not prove successful.

Despite this, however, the flow in the working section is very good.

Fig. ₄₃ shows the fall in water level over the length of the

contrac-tion over a rarge of speeds, and it may be seen that this compares

reason-ably with the theoretical values.

X. GENERAL CONCLUSIONS

The prime reason for constructing a scale model of the proposal NPL circulating water channel was to study the stability of the proposed unorthodox circuit, and all of the experimental evidence is encouraging

in this respect. It would appear, however, that if there is any variation in the set speed of the impeller, then fluctuations will occur in the sur-face level and speed of the flow passing through the working section.

Measurements of velocity distribution across the model working section are generally very good and there is no evidence of surface retardation. The velocity along the working section increases by approximately 5% and it is thought that this is mainly due to the thickening of the boundary layer on the bottom of the channel, consequently there will be a slight increase in speed over the length of the model hull on the prototype.

Model experiments to investigate the possibility of using an adjus-table false floor to vary the effective working section depth, indicate that the flow is no worse than that encountered when running the channel at reduced depths. There is a strong possibility that the velocity at

low effective depths will not be time constant, and for this reason, it is doubtful whether the prototype will be useful below about ₄ ft depth.

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There is an indication that it may be possible to maintain a horizontal water surface in the working section by inclination of the floor, although probably not under all conditions. To reduce the

friction loss over the working section the friction coefficient of the bottom and sides should be as low as possible. Particular care must be

taken to prevent any undulations in the walls of the working section to minimise the possibility of wave formation.

Because of its novelty the cascade weir was subjected to very exhaustive tests and there was every indication that it was superior

to the tilting weir. The draw down was less with the cascade weir, and there was very little increase in velocity immediately upstream of the

weir. Using a cascade weir, it is possible to reduce the length of the

weir section, although provision should, be made for the installation of

a tilting weir at a later date if the model predictions are not verified

on the prototype.

Experiments have shown the arrangement of pump and sump to be perfectly satisfactory. Structurally there are advantages in further slight modifications to the pump inlet arrangements, but these will make no fundamental change to the design tested.

Experimental evidence illustrates the effectiveness of the rubberized hair screens in reducing the air entrained by water passing over the weir and, since the forward velocity is low in this area, the loss of heaa across these screens is negligible. Floating a heavy wooden raft in the area adjacent to the pump inlet may tend to damp out any head fluctuations above the pump and also serve as an inhibitor to the formation of air

entraiming vortices.

Comparison of the MoW and SHL design diffusers indicate that the

SRL design gives slightly less flow asymmetry, but subsequent experiments on screens in the upstream stilling area indicate that the poor flow at exit from the diffuser can be considerably improved. Since the MoW

design is simpler to construct it is intended to fit this to the prototype and to use screens to rectify any irregularity of flow before it reaches

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19

-Experiments on the model, three dimensional, free surface contraction have resulted in the production of a flow of high uniformity in the working

section. However, in order to effect changes on the prototype if required,

a method of construction has been proposed by MoW which is capable of final adjustment.

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RE VEREN CE S

ORKNEY, J.C. - The development of a hydraulic flume for ship model testing - B.S.R.A. Report No. 165,

_1955.

WILLIAMS, E.E. -

Design of a recirculating water channel

-NPL Report, unpublished.

DENNY, P.F. -

An experimental study of air entraining vortices in

pump sumps - The Institution of Mechanical Engineers, November

_1955.

BAINES, W.D.

and

PETERSEN, E.G. -

An investigation of flow through

screens - The American Society of Mechanical

Engineers,

_1951.

DRYDEN, H.L. and SCJ-IUBAER, G-.B. - The use of damping screens for the reduction of wind tunnel turbulence - Journal of

(25)

21

-BIBLIOGRAPHY

SAUNDERS, H.E. and HUBBARD, C.W. Circulating water channels

-SNAJ1E 1944. Page _325.

SCIT[JSTER, S. - Der Wasser-Umlaufkanal der Versuchsanstalt fr Wasserbau und Schiffbau.

SAUNDERS, HE. - T.M.B. Report C -

₅₇₄

B, Page

87.

cli BELLA, A. - La Vasia a Circuito Chusso Dell - Universita di Genova.

t

FLUG-EL, G. - Ergebnisse aus dem Strumungeinstitut der Technischen Hochschule Danzig - Jahrbuch der Schiffbautechnischen

Gesellschaft,

Vol.31 1930.

BAXER, G.S. - William Froude National Tank - I.N.A. 1912 Page

58.

OKADE, S. - Investigation on the effect of the angular velocity

of steering upon the performance of rudder - Tecim. Res. Lab., Hitachi Shipbuilding and Engineering Co.

Ltd. Aug.

_1958.

WRIGHT, EA. -

Some international aspects of ship model research

(26)

FLOW STABILITY IN WORKING SECTION

Cascade Weir - free flooded Depth in Working Section - IO in

For definition of Q see fig.IB Speed in Working Section (ft/sec) Weir angle (Q) (degrees) Analysed Motor RPM Maximum amplitude of surface ripples (in) Magnitude of surge (in) Period of surge (sec) Remarks O.13 80 300

0.005

0.005 ₃₇

0.4.7

79

333

0.005

0 O

0.58

79

320

0.005

O Change in level in working section during experiment but not a surge 1.19 60 4.35

0.025

0 0

1.8

50

586

0.025

0 0

2.02

).-8

670 -

Change in water level of

0.027 in

but no obvious surge

2.38

4.0 735

0.035

0 0

3.09

37 935

0.010

O O

3.17

35 932

0.020

0.04.

35

3.25

34.

990

0.015

0.035

50

(27)

TABLE 2

FLOWSTABILITY IN WORKING SECTION

Cascade Weir - free flooded Depth in Working Section -

9-

in

For definition of Q see fig.IB

TABLE ₃

FLOW STABILITY IN WORKING- SECTION

Cascade Weir

Depth in Working Section - 9 in Speed in Working i Section (ft/sec) Weir angle (Q' (degrees$ Analysed Motor RPM Maximum amplitude of surface ripples (in)

Magnitude

of surge (in)

Period

of surge (sec) Remarks 0.57 88

₃₉₅

-

0.015 32 1.00 70

)26

0.01 -

-1.147 60 515

0.03 -

-1.96 50 6214- 0.03 - - radual change in water level 2.61+ 10 807 0.03 - - Change in level of about 0.005 in over 180 sec 3.18 ₃₅ 901 0.005 - - Random level changes of about 0.03 in

but not periodic

O.i18 81

366 -

-

-1.07 70 14146 0.005 - - Movement of

water surface

but not periodic

1.57 60 ₅₃₃ 0.015 - - Rapid change in

level but not

periodic

1.98

50 621

_0.037

-

-2.80 10

768 -

-

Water level change of about 0.035 in but

not periodic

3.1 ₃₅

880 -

0.01 A definite oscil-latory movement of about 0.01+ in

(28)

FLOW STABILITY IN WORKIN( SECTION

Cascade Weir - varying degrees of flood Depth in Working Section - 9

in

Speed

in

Working Section (ft/sec) Head drop over weir (in) Magnitude of disturbance in channel working section (in) Remarks

3.21+ ₁₊ Small Artificial surge close to weir in sump causes change in level in working section but not a periodic

surge

1.18 1 Too large

to measure

Slight disturbances in sump cause very large movement in working

section

1.36

3 Too large

to measure

Same as for 1.18 ft/sec

1.09

1- Too large

to measure

Sanie as for 1.18 ft/sec

0.72

6

0.15

Not as bad as previously but after ceasing artificial surge in sump about

3.5

sec for surface

of working section to cease movement

0.62

9

0.07

About 1+ seo to show in working

section after commencement of artificial surge and about

3.4

sec to stop after stopping

surge creation in suinp

o,61 11 No movement

0.61+ 11 - Artificial surge created over

pump but no movement going back since it is largely damped by

screens in sunip, and weir is free flooded. Seems to indicate that even violent movements in sump are damped out before going around the circuit to the working section

1.08 1- Too large

to measure

The same as above but with weir

not free flooded. Confirms that any movement travels back up-stream when weir is not free flooded

(29)

TABLE ₅

FLOW STABILITY IN WORKINC- SECTION

Tilting Weir Free flooded Depth in Working Section - 10 in

For definition of see Fig.IC

TABLE 6

Tilting Weir - Free flooded.

Depth in Working Section - 9 in

Speed in Working Section (ft/see) Weir Angle (4) Analysed RPM Maximum amplitude of surface ripples (in) Magnitude of surge (in) Period of surge (sec) Remarks 0.72 19° - )'

470

0.002 0.005 36

1.125 12° - 52' 5LO

_0.005

0.02 70 Surge appears to be genuine and analysis of record of pump revs, shows no

fluctuation

1.72 100 ₆₃₁ 0.002

0.007

2.16

8° -

20' 731f

-

0.02 22.5

2.47

6° - 20'

780

0.010

0.03

30 Motor speed fluctu-ating corresponding to fluctuations of water speed and to

period surge

0.417 17° -

26'

404 -

-

Change in level of 0.010 in but not periodic 0.93 15° - 6' 8o - 0.016 33 1.195 12° - 6' 520 - - - No obvious movement

1.385 10° -

12' 600 - 0.015 ₇₅ Appears to be more a

change in level than

a surge

2.38

80

700 -

-

Absolutely steady

2.95

3° - 36' 900 - - - Change in water

level of about 0.013 in

(30)

Tilting Weir - Free flooded Depth in Working Section - 9 in

For definition of Q see Fig. IC Speed in Working Section (ft/sec) Weir Angle (Q) RPM Maximum amplitude of surface ripples (in) Magnitude of surge (in) Period of surge (sec) Remarks

0.11.3 200 - 6' 230 0.012 - - Very slight water movement

0.35 16° - 181 310 0.008 - - Slight movement, not periodic

0.95

12° - 36' ₄₅₀ 0.003 - - Movement in level of about 0.025 in

but not periodic

1.4 90 510 - 0.025 42

2.02 70 - 12' 620 - - - Increase in rpm of

about 1% causing a change in level but not periodic

2.56 5° - 22' Not taken

- _0.35 64 Surge improbable, only random move-ment of surface, doubtful whether genuine surge 2.77 40 - 10' 880 _.015 - - Movement of water surface, not periodic

(31)

TABLE 8

Tilting Weir - Varying Degrees of Flood Depth in Working Section -

9.6

in Velocity in Working Section - 0.5 ft/sec

Weir Angle Q -

17°6'

Head Drop Over Weir (in) Amplitude of main surge (in) Period of main surge (secs)

Time from

commence-ment of exciting force to appearance of movement in Working Section Remarks

2.08

0.030

38 Almost Instantaneous

Surge created next to weir of period

1-3

sec

2.08

0.017 i6

2.3

sec Surge created in

sump causing movement next to

weir in sump of

about I in

0.78 -

-

2 sec Induced, movement

adjacent to weir

of about 2-i' in.

No apparent long

period surge

2.38 -

-

Instantaneous Exciting force next

to weir. Slow

small movement of

surface

3.88 -

-

Instantaneous Two distinct peric

of exciting force applied. No

apparent surge but slight movement

5.08 -

-

Instantaneous No obvious long

period surge but

still slight

movement of water

surface

9.58 -

-

Instantaneous No long period

surge. Slight change in water level

(32)

TABLE 11

Vertical Velocity Distribution in Working Section

Cascade Weir

TABLE

12

Tilting Weir Model Vèlocity (ft/sec) Prototype Velocity (ft/sec)

0.25

0.79

0.5

1.58

1.0

3.16

1.25

3.95

2.25

7.11 2,5

7.90

35

11.06

Model Velocity (ft/sec) Prototype Velocity (ft/sec)

0.5 1,58

1.0

3.16 1,5

L74

2.0

6.32

25

7.90

3.0

9.48

Nominal Speed (ft/sec) . 0 2 0 3

Distance of particle from bottom (in)

9.6

9.2

9.0

8.2

4.2

9.3

7.0

6.8

4.6

4.)4

9.5

8.1

7.3

6.4.

5.7

3.5

Speed factor

726

725

725 7L1

724

34.9 34.9

3°

34. 34.7 441

)2

4.39 4.38 4.38 4.32 Nominal Speed. (ft/sec) 1.0

3,5

Distance of particle from bottom (in)

9.4

9.1

6.8

6.5

5.2

3.7

0.6

9.6

8.4.

7.6 6,2

5.8

5.7

3.8

Speed Factor 454.

437

424-4-37

440

4.31 396

523

521 521

516

524

526

528

TABLE 9 TABLE 10

Cascade Weir

(33)

TkBLE 13

Working Section Surface Level

False Floor Fitted

+

indicates slope upwards downstream

- indicates

slope downwards downstream

Water Depth at

entrance to

Working Section (in)

3.6

5.6

7 O

-20

+20

+120 +80

-20

O

+2O

+20

at

0.5

ft/sec +880 +750 +860 +1000

860

+670 +860 +860 at 1.5 ft/sec +6000

-30O

-1500 -860 -1000

+000

+1330

+0O0

+860

at 2.5 ft/sec

-200

Standing

Wave

Standing

Wave

Standing

Wave

Standing

Wave

Standing

Wave Standing Wave -550 Standing Wave

(34)

Pump Inlet Flow Conditions Figure No. Submergence Diameter Ratio Pump Inlet Speed (ft/sec) Screening in sump Remarks

22 2.67 7.J No screen Cushes of air rising

just before pump.

Surface unstable. No Vortex

23 2.88 6.95 1 screen Air rising just before

pump considerably less

than 1. No vortex

2.13 7.10 1 screen Vortex appeared.

Consider-able air rising (about 60%

of surface)

25 2.10 7.00 No screen Vortex as in 2) but not as strong about 80% bubble

cover of surface

26 1.5 6.7 No screen No vortex. reat quantities

of air rising

27 1.44 7.0 1 screen 2 strong vortices. About

80% bubble cover of surface

28 2.67 7.55 2 screens close together

Tendency for vortex to

form. Air considerably reduced

29 2.67 7.30 2 screens far apart

No vortex. Water surface

excellent

30 2.13 7.3 2 screens

far

apart

No vortex. Water surface

good but few more bubbles than 29

(35)

TABLE 15

Screens in Upstream Stilling Section -Experiment Conditions

TABLE 17

Contraction Plow Observations

TABLE 16

Velocity Traverse in Working Section - Experimcnt Conditions

Model Speed (ft/sec) Corresponding prototype speed (ft/sec)

0,5

1.58

15

25

7.90

Model Conditions Corresponding prototype conditions Speed in working section

1 .5

ft/sec _L4.75 ft/sec Depth in working section

9.6

in 8 ft Distance from diffuser at which traverse was made 10.5 in

8.75

ft Figure No. Water speed in working section (ft/sec) Distance of hypodermic below water surface (in) Remarks

0 ₅ On bottom Potassium permanganate crystals dropped in to show flow on bottom

15

0.5

18 Flow pattern seems very good

0.5

12

-do-47

0.5

6

-do--48

1 ₅ 6

The valves on injection apparatus not working properly so valves opened

wide

49

1.5

12

-do-50

1.5

18

(36)

-do-(

DIFFUSER UPSTREAM SII WN' ION

\

WATER LEVEL

WOI

SECTiON

\\

DROP

'

ER WEIR SUMP

i

REThRM CONDUII

IZDIA.

L

WATER LEVEL EL VATI ON

CONTRACTION

PLAN

FIG. IA. GENERAL

LAYOUT

OF

CIRCUIT

FLOW

WORPJN SECTiON WATER LEVEL ¡N WORKING SEC11

WEIR _SECTiON

DRA WOOWN

SUM P

Ï

HEAD DROP

ovg wEIr

SUMP WAT LEV EL

FIG. iB.

DETAILS OF CASCADE WEIR

FIG. IC.

DETAILS

OF TILTING

WEIR

s

QF

4/

(37)

WIDTH OF CHANNEL LOOKING UPSTREAM

EFFECTIVE DEPTH IN MODEL WORKING SECTION 36 INS

NOMINAL SPEED IN MODEL WORKING SECTION IFT/ SEC. POSITION OF TRAVERSE - ENTRANCE

WITH FALSE FLOOR

o

I-w

LI

_u

Z O

(

) DENOTES FLUCTUATIONS > 1o10

VELOCITY TRAVERSES ACROSS WORKING SECTION

FIG 2

EFFECTIVE DEPTH IN MODEL WORKING SECTION 36 INS NOMINAL SPEED IN MODEL WORKING SECTION lET / SEC. POSITION OF TRAVERSE - ENTRANCE

NO FALSE FLOOR

3"-443

441

440-440---439

I I

440-440----I I I

437 -440

I I j

2"-439---437

437 437

434-435 -435

437

440

I I I I

(437)-(424)

I"-(432

433 432

434-(436) -435-436

I I f I I i J I 6"

4'

2" I" O I" 2" 4" 6" I I

(425')-428---(429)

432 I

3"--(427)--428

I I 430 431 I

432-I

2"-423

432 431- 429

430-432-431

430-430

I I I I 423

I' -(338)-429

429 427 428

430-428

429-I I I I I" i O" I I I" 2" 4" I 6" 6" 4" 2"

(38)

EFFECTIVE DEPTH IN MODEL WORKING SECTION 36 INS NOMINAL SPEED IN MODEL WORKING SECTION I FT/SEC. POSITION OF TRAVERSE - EXIT

NO FALSE FLOOR

3(45O)---- 481

480 481 484 485 484 479 481 I I I i I i

2(4O5)---484

486

485 482

485- 486(487) -

489-I I I I I i I

(4I0)(432)----

474Ç446

-I I I t I

4" 2" I" O" I" 2 4

WIDTH 0F CHANNEL LOOKING UPSTREAM FLUCTUATION VERY BAD I"rROM BOTTOM

FALSE FLOOR O I-o

_{3"(398)(464)(465)---457---- 454}

456 455

453-444---I I I I

o z

2"- (380) - (473) (475) (475) 474

474 473 475

466

-LL

I

o

It

-

- (47) -

(42) (4I) -

(4)-za

6 4 2 h _O" I 2

4'

- I-(n

a WIDTH 0F CHANNEL LOOKING UPSTREAM

FLUCTUATION VERY BAD I"FROM BOTTOM

( )DENOTES FLUCTUATIONS > I0/

(39)

EFFECTIVE DEPTH IN MODEL WORKING SECTION 36 INS. NOMINAL SPEED IN MODEL WORKING SECTION I 5 FT/ SEC. POSITION OF TRAVERSE -ENTRANCE

NO FALSE FLOOR

A TRAVERSE WAS NOT MADE AT THIS CONDITION SINCE FLUCTUATIONS

THROUGHOUT CROSS SECTION OF CHANNEL WERE VERY BAD.

FALSE FLOOR 3 459 668 667 t I Z

2-(695)----7O2

698

u-I

I I (615) 699 696 I, L 6 4 2 I-J)

(

)DENOTES FLUCTUATIONS > I

0/

VELOCITY TRAVERSES

IN WORKING

SECTION

FIG 4

665 668 665 (66e) 665

.668-I I I

(696)-696-

696 696 690 689 I

695 -(676)

-696

695- 697 697 t I_ i I O I 2 4 6

(40)

O I.- I-O

n

O

'r

u-O

EFFECTIVE DEPTH IN MODEL WORKING SECTION 36"

NOMINAL SPEED IN MODEL WORKING SECTION 20 FT/SEC. POSITION OF TRAVERSE ENTRANCE

NO FALSE FLOOR 3 8(0 (816) (815) 808 808 807 608 809 805

2' 805

833 - 830-

826 (828) 829 - 829

830 832 I I I I I

i" (824)(82o)--Ç825)--(820) 812 (820)(825) (825)

(825)

I i I I I I 6

4'

2 I O' I 2b 4" 6'

FALSE FLOOR 3" 779

780-780 (779) (780) (782) (784)

778 -(778)

2e (802)

811 810 809

809

8(1 810

608 - 8(0

4' i I I I I I i

i (716)

816 8(5

8(0-807

8(0 811

soo-(soo)

I i i I I 6 4 2 I 0" I' 2 4 6H

WIDTH OF CHANNEL LOOKING UPSTREAM ( ) DENOTES FLUCTUATIONS > I 0/

(41)

o

VELOCITY TRAVERSE ACROSS WORKING SECTION

FIG 6

EFFECTIVE DEPTH IN MODEL WORKING SECTION

36'

NOMINAL SPEED IN MODEL WORKING SECTION 2-0 FT/SEC

POSITION OF TRAVERSE -- EXIT

NO FALSE FLOOR O 3'

(875)(941) 938

929 927

932 (931)

930 929

z

_I I I I I I 2

(865)(947)---(943)----(942)--- (950) (948) (951) (951)--- (ess)

U.L) I I i I I i w

(870)(920) - Ç880)(895)----(880)--(88O)--(920) (coo) 945

ULL I

z O

_t , j, n 6

4'

2' I O' I" 2 4 6

WIDTH OF CHANNEL L00KNG UPSTREAM

) DENOTES FLUCTUATION>3/4 0/0 FALSE FLOOR 3'

(720)

866 (866) (866)

866

(o5)(8os)a74 (848)

2' (813) 905

908 908-908 908 910

91Q(897)

I i i I I

(836) (900)(899)(89o)--(868)--(87o)(895)Ç903)(830)

6* ₄ _2' _I"

_0'

_I'

_2"

_4'

6' WIDTH OF CHANNEL LOOKING UPSTREAM

(42)

NOMINAL SPEED IN MODEL WORKING SECTION I-O FT/SEC

6"

419-418- 419- 417-419---415

417-419

417

o

I I I I i I I I t-t- 5

437-435

436-435-434

433-434---431-431

I I I I I * W 4

435- 435-436---- 434-434-435---434---430--431

J I I I I

438 -439 -438 -436--

Il

_433-.,.-

430 -431- 429- 436

WO I I _i I I I

Ou-

I

2'

434

435-434-432---437 -438-436-437

t- i 43 1/) ¡ i i I i J I" FLUCTUATING>2°/O i I 6" 4*

2'

I O'

I'

2'

4'

6'

WIDTH 0F CHANNEL LOOKING UPSTREAM

VELOCITY TRAVERSE ACROSS WORKING SECTION

POSITION OF TRAVERSE - ENTRANCE

NO FALSE FLOOR

6'

40B-409---

407- 406- 406- 406- 406

-409 -407

O t t I

I-o

5'

433434-434----433-436

435--433---430

4" I I I I I W ₄₃₁

430 -431-- 430- 428 -428 -428---426 -420

3'

431¡ I I I u.

429-428---429---428-427

429- 429 -429

WO

O 426 I I I

Z

'-<O

t-2'

427-426-426-427---427----425-425-427

t t I I i

420-426-424---426-

424- 427-426-427-427

Io 6 I _I i I 4"

2'

I'

0'

I'

2' 4"

(43)

NOMINAL SPEED IN MODEL WORKING SECTION 10 FT/SEC.

POSITION OF TRAVERSE - EXIT

O d

-z

0<

IX

I

u-I f

4l(466)Ç456)(466)--47548I(474)

FLUCTUATING NOT TAKEN

I J 2" I" O" " 2" 4'

400

418 I O 5

(380) 436

435 433

435-434

436 429 (410) I-O -J

t)

i I I I 4"

(s

430 428 430

429 429 428

426 (410)

z

_I _I _¡ I I

0<

IX

I

3 (480) 431 430 429

429-428

427

427 (425)

u- U 2" (345) 419

(a 6) (425) - (425)(425)

-

(426) (4 28)

I I

I" FLUCTATING SO NOT TAKEN

I J I' I I

6" 4 2 I O I 2 4 6

w I 1 4 * II

WIDTH OF CHANNEL LOOKING UPSTREAM DENOTES FLUCTUATIONS > I0/

VELOCITY

TRAVERSE ACROSS WORKING SECTION

FALSE FLOOR

422 (412)

I

FIG B

NO 6* FALSE FLOOR i I 5 (454) 464 I 4 (462) 470 I I 470 3 470 I 2" I (462, (473) 6' 4 421 421 421

422-421

I I I f I NOT TAKEN I i 419 463

467-468

i I I I

4740)

468 469 467 I I 467

466)-(457)

469 471 472 471

469 464 469 470

(44)

EFFECTIVE DEPTH IN MODEL WORKING SECTION 63 INS NOMINAL SPEED IN MODEL WORKING SECTION I-5FTI SEC.

NO FALSE FLOOR 6 NOT TAKEN g 5 661 664 660 660

660 - 660 - 660- 660

660 I I I I I j 4"

679- 670- 667

668

670- 668- 667-666 -668

I I I I I I < ₃

677-677- 675- 673-674--- 673

674-674

676 I I 2

673 - 674

672

673 - 672- 671

670 - 671

675 I I

i'

(654')- 668

663- 663- 668- (668)- 668 -668- 66!

O I i I i u 'q I, I 6 4 2 I O I 2 4 6

FALSE FLOOR 6'

625-O I-I- 5

649-I z 4

664-t I

I

3

665-625- 624- 627- 626 - 625

653- 652

653 653 651 I I i I

668-668-667-666-664

I I

666-667----668

664-(666)

wo

I I i I I I Q U-

f

647- 658

657 657 657

656- 655

654-657

z0

I I

I"

(574)- (590)-(6I6)-

(6I0)-(599)---(6I0)-(59O)--- (59o)(59o)

O

I I I I I

6' 4" 2" I 0" 1" 2" 6"

WIDTH 0F CHANNEL LOOKING UPSTREAM ) DENOTES FLUCTUATIONS >

VELOCITY TRAVERSE ACROSS WORKING

SECTION

627 625

624

-653 654 652 I I 667 I 669

668-I 666 666 665

(45)

O I-O O a: u-6

VELOCITY TRAVERSE ACROSS WORKING SECTION

FIG IO

EFFECTIVE DEPTH IN MODEL WORKING SECTION 63 INS NOMINAL SPEED IN MODEL WORKING SECTION 15 FT/SEC. POSITION OF TRAVERSE - EXIT

NO FALSE FLOOR NOT TAKEN I I 5 (790)

701 - 699 - 697

698 695

698 - 701

f687) I I i 4 715

735- 734

730-732- 733-734---732-

(72O) I I i I 3

(705)-741 - 740

739- 742- 742

747 748 745 I _I I I i I 2

(710)- 747- (740)- (735)- (737,) _747

7D -75O

(743

I FLUCTUATING SO NOT TAKEN

I I

I J

6 4 2 I O 2 4 6

FALSE FLOOR 6

(600) - (639) -644

643 -643 -642

642 -(643)

(633) I I I 5

(600)-667

671

669-(669)

672- 670-(67-(665)

I I i I i I 4

(620)-(683)--- 684- 682-682

677

681- 679-(668)

I I I 3

(565)- 676- 676

676-676

676

678-(676)--- (669)

uJO I I I I L) _u. 2 (617)

(670)- (675)

673)

(67O)(665)(666)

(58)

(650) I i I i I

I FLUCTUATING SO NOT TAKE

I I I I i I i I

6 4 2 I O I 2 4 6

( ) DENOTES FLUCTUATIONS > I 0/

(46)

NOMINAL SPEED IN MODEL WORKING SECTION 20 FT / SEC.

NO FALSE FLOOR 6'

877-882--- 878- 879- 878-879

874-879---878

O I-. I I :ç

5'

916- 916

₉₁₅

915-911-908

911- 912 -912

I I I i 4"

916-914----913-914

912

9I2--915----913---914

O I I j I I 918 916

914-913

913-911 -911-907-911

u.S _1 ( ¡ I I I I U t 2*

919 -919 -920--- 914- 913 -916-918 -917---919

zo

I i j I I

I'

914 917

907-913----916---92I---920-923-923

I I I I I 6"

4'

2 I"

O'

I'

2 4" 6"

FALSE FLOOR

6'-(871)----874

877- 877- 874- 976- (975)_(873) -(871)

I I I I

892-891

890-891----891----890----890----%90----888

I I I I I I

904-906- 902- 903-905- 907-902- 900-902

I I I I

906-910- 906-907- 905903-903902

903 I I I I _I I

860-902-898 - 897 - 898-896- 899 -894 -(897)

I I' NOT TAKEN o I I Id 6"

4'

2"

I'

O" 2 4" 6

( ) DENOTES FLUCTUATIONS >

VELOCITY TRAVERSE ACROSS WORKING SECTION

'-

5'

4'

3 u. I', u.

z0

2"

(47)

FIG. 12

NOMINAL SPEED IN MODEL WORKING SECTION 2 O FT/SEC POSITION OF TRAVERSE -EXIT

NO FALSE FLOOR

NEAR SURFACE NOT TAKEN

5'

(962)_IOOO 998

999

998 1001

iOOI 1005 (975)

4'

(955)IOI9---- 016

1014 1017 1Q18

OI6

1016 1016 I I

3'

(c75)I"s---lO26

1020-1022---1025

1027

lO2EIO22

I I I I I

2" FLUCTUATING SO NOT TAKEN

-I FLUCTUATING SO NOT TAKEN

I I I i

4'

2'

I'

O" 1' 2"

4'

FALSE FLOOR ob

____Ç863)_ç863)

₈₆₁₈ s"

(740)-917

915 913 915 (914) 914 915

990

4"

(78o)(923)

931 931

930

931

930(916)

I _I I I 3«

(960)(933)

936 935

(935)(934)---- 935-- (930) (925)

2

(92 6) 915

(908) -

(91 2)

(903)

I'

SP0TS NOT TAKEN AS THOSE FLUCTUATING TOO BADLY

I I I I I

6" 4" 2 I" O" I" 2"

4'

6

(

) DENOTES FLUCTUATIONS > I 0/

(48)

fJ

z

o

t 00

TLLTNG

WEtR

CASC1\DE V'IJR

i.000

2S Fi/SEC

1000

j.ri SEC

i.00

t023

tO20

I.0i

IOI6

100

L9

LSÇC4T°t9 _rl___

t. 053

oss

1.04_7

I0S3

1040

z

o

ti

w

1206 O76

-125_7

--.---.---_--t'054

Q io

to

30

40

50

60

80

DISThNCE FROM BE

NIÑG OF W0RKIG

SECTION

I E 1 I

4

3O

55

_7O"

POINTS

AT WHICH

MSUREMENTS WERE

TAKEN

LONGITUDINAL

VELOCITY

TRAVERSE

-41/2 FROM

BOTTOM

OF CHANNEL

(49)

TILTING

'NER

CASCP¼DE WEIR 0.S9

5 FT SC

1000

15 FT SEC

003 _{1004 o.}

-rT SC

1' 021

(022

I 02 I 1020

I0 O

1048

tO40

1040

z

o

ti

w U, (9

z

o

L

o

'J

z

ItJ 1'192 fZ18 107

I360

186

----..---1 082

- .---____.

.063

z

o

w

(I)

w

t'-

o

z

IJ

0 IO'4

jO

20

30

40

50

GO

70

80

DISTPNCE

FROM BEGINNING

OP WORKING SECTION

I I I i I 'Y. 30" -, O"

er

POINTS

AT WHICH

MtASUREMENTS WR TAKEN

LONGITUDINAL

VELOCITY

TRAVERSE - 6" FROM

BOTTOM

OF

CHANNEL

(50)

O

w

(n (D

z

1000

OSSB

t000

OG FT SE

TILTN

WEIR

z

CASCADE WEIR

O

z

o

w

1.719

2 o

Líi ta

o

O

û

I

O

z

Id

bi

iO4S

-p046

1383

1060

---¶024

s,.

IO3

1040

O i0u4

IO

2u

30

40

50

60

10 DISTANCE

PROM BEGIÑNG OF WORKING

SECTION

I I I I I _81"

4.

'30"

55"2"

POINTS

AT WHICH

MASUREMEÑTS WERE TAKEN

LONGITUDINAL

VELOCITY

TRAVERSE - 8" FROM

BOTTOM

OF

CHANNEL

(51)

z

o

s-

(j

hi CI)

TftNG WIR

CASCA

WEIR

O 97

z

o

s-

u

w (j) (-9

z

o

IL

o

z

LAi

i-liz

fO43

o'

o

20

3O

40

SO GO

O'9 G

bISTANCZ

FROM B.GiNNtNG

or WORKING

SECTION

10

8O

-.-30"

0"

61"

POINTS

AT WHICH

MEASURZMENTS WR TAKEN

LONGITUDINAL

VELOCITY

TRAVERSE - 9" FROM

BOTTOM

OF

CHANNEL

11 -Ö

(52)

DEPTH = 9-6 INS

36-8--37-7-36-6

36.4 36-5---36-6--- 37-5---38--5-382

I I i I I

7.5

35-7-40-0-39-2 -39-0---- 39-O -38-9---39-3---40-3

_39-0

I _I I

6-5'-- 4I-9---423-4I-7

41-2---40 B-41-I -41-4--42-2

40-I

I I I I i I t

5-5-40-8-43-O-42.! -41-6----4 I-3---41'3----41 9-42-6

41-I

I i I

4-5-40-243-I- 42-2

41-5

4I'5- 41-6 -42-5-433 -40-8

I I I I I I

3-5----37 9-42-3---41-5---- 4!

I 40-9---41-3 416 42-6 40-O

I J J I I s

2-5---37-2

41-5-40-5---40-O- 39-9--40-I-40-5-41 5

38-3 I I

I-5----33-7-38-4-3B-I----37-5

38-I---37-6-- 375- 39-5 -346

I I I I

0-5 -30-5 -30-4-29-9--29-5

30-3 -29-5 -29-7- 307 - 30-0

I_

I.,

IV I., 1

JI

IR 6-7

54

3-6 I 8 0 I-B 3-6 5-4 6-7

WIDTH OF WEIR SECTION LOOKING UPSTREAM

(53)

FIG. IB

NOMINAL MODEL CHANNEL SPEED = I-O FT ¡SEC.

li _9-6INS

36-3-38.9-38-5-38-9---38.7--39.7-35.5.. 38-7- 38-7 -38 -7--38-5

I i I I I I I I

75 - 35-0-39-I-39-O - 391

39-I

39-0--39-O---- 39-0- 39-0-39-0 -381

I I I I I

6-5--32-4-38-0-39-0-39-0

38-9--38-9-38-9-- 39-O- 38-9 - 38-7-32-4

I I I

I I

55-335--38-7-39-I---38-9

39.0-38.9--38-9-- 389- 39-I - 39-O-36-0

I I I I I I I

45 -35.9- 38-9-38.9- 38-9

389-38-9-38-9-- 38-9- 38-8

38-9--36-I

I J I I I I I I

3-5'---38-5---38-9-389---38- 38-S--38-8--38-8 - 388 -38-9 - 38-8--35-0

I I I I _I I

2-5'--- 33-2 -38.1-39.0 - 39-O - 38-9-'-- 38-7 -38-7--387---39-O

- 387 -33-2

I I I I I i

I 5

33.3 -38-I -39-I -39-0-38-8 -.38-7-38-9 -38-7 -39-I - 38-7--33-3

I I I I I I

6-7" 6

O'

2-5'---- 0"

2 5'- 30'- 4-5"---- 6,Ou_6.7

WIDTH OF WORKING SECTION LOOKING UPSTREAM

VELOCITY TRAVERSE AT DOWNSTREAM END OF

(54)

z

o

o -J

J

>

w

-JO

w

I-O

z

0

o

60

65

70 75

80

8S

DISTANCE FROM START

OF WORKING SECTION (INs)

TILTING

WEIR - DRAWDOWN

WEIR SECTION

OES FT SEC FT SEC 1879F1 SEC e 63 FT SEC

(55)

flLTIN

WEIR

CASCADE WEIR

FIG. 20.

/

I

/

,

/

0

05

10

16

20

25

30 SPEED N WORKING SECTION (rr/sEc)

SLOPE OF WATER

LEVEL

OVER

LENGTH

OF

WORKING

SECTION

AT

VARIOUS

SPEEDS

ooOz

o.00i

o

l'-o'

L1J

oZ

_.iW

tPJ

(56)

(D FLOW

ELEVATION

H-15 +

z'

WI

bi'

L)'

PROPOSED

GENERAL

ARRANGEMENT

OF

SUMP

40

'I

PUMP

t

7/)

(57)

FLOW

IN

SUMP AT

PUMP

INLET

(58)

(59)

(60)

(61)

(62)

(63)

(64)

(65)

FLOW

IN

SUMP

AT