A HYDRAULIC MODEL STUDY OF THE PROPOSED PUMP-INTAKE AND DISCHARGE FLUME:

FLORIDA POWER CORPORATION'S CRYSTAL RIVER HELPER COOLING-TOWER PROJECT

by Tatsuaki Nakato

Sponsored by Black & Veatch Engineers-Architects

1500 Meadow Lake Parkway Kansas City, Missouri 64114

IIHR Technical Report No. 339

Iowa Institute of Hydraulic Research College of Engineering The University of Iowa

Iowa City, Iowa 52242-1585

April 1990

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ABSTRACT Using a 1:10-scale laboratory model, the performance of the proposed pump-intake and cooled-water discharge flume was evaluated for the Florida Power Corporation's Crystal River Units 1, 2, and 3 helper cooling-tower project. Nonuniform pump-approach flow distributions were rectified by means of arrays of baffle blocks; subsurface vortices were suppressed by means of floor and backwall splitters as well as sidewall-floor-corner and backwall-corner fillets; and a horizontal grating was devised to suppress formation of free-surface vortices. A hydraulically efficient configuration was also developed for the proposed, cooled- water discharge-flume outlet structure.

ACKNOWLEDGMENTS The model investigation reported herein was conducted for and sponsored by Black & Veatch Engineers-Architects in Kansas City, Missouri. The author extends his special thanks to Messrs. Gary Christensen, Thomas Kaczmarski, and Charles Field of Black & Veatch for their unfailing cooperation and their valuable input throughout the entire course of the study. The author also expresses his special thanks to Messrs. Joseph Lander of Florida Power Corporation, and Robert Cornman and Jeffrey Galush of Ingersol-Rand Pumps for their suggestions given during the review meetings. Mr. James Goss and his IIHR shop crew built the excellent model. Without their skilled craftsmanship, this project could not have been completed. Finally, the author expresses his thanks to Mr. Marc Weinberger who served as an undergraduate Research Assistant in collecting experimental data, and Mr. Michael Kundert for his skilled draftsmanship.

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TABLE OF CONTENTS

page I. INTRODUCTION 1 A. Background 1 B. Scope of Study 1 II. PUMP-INTAKE AND DISCHARGE-FLUME MODEL 3 A. General . 3 B. Equipment and Test Procedure 4 C. Criteria for Satisfactory Pump Operations 8 III. PUMP-INTAKE TEST RESULTS 8 A. Description of Preliminary Model Screening Tests 8 B. Description of Developmental Tests 11 C. Presentation of Final Optimization Test Results 14 IV. DISCHARGE-FLUME TEST RESULTS 18 V. RECOMMENDATIONS 21 LIST OF REFERENCES 22

LIST OF TABLES

page Table 1 Summary of possible pump-operating conditions 23 Table 2 Summary of measured vortimeter speeds under the as-designed

conditions 24

LIST OF PHOTOS page

Photo 1 The 1:10-scale model (looking downstream) 25 Photo 2 Model intake bays (looking downstream) 25 Photo 3a Model suction lines 26

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Photo 3b Close-up view of suction lines . 26 Photo 4 Discharge flume (looking downstream) 27 Photo 5 Model suction-line system 27 Photo 6 Model dual-flow screen-support frames 28 Photo 7 General flow pattern in front of the intake 28 Photo 8 General flow pattern surrounding traveling screen (Bay 1) 29 Photo 9 Air-entraining free-surface vortex in Bay 4 29 Photo 10 Air-entraining free-surface vortex in Bay 4 30 Photo 11 Pump-approach flow pattern in Bay 4 with final fixes 30 Photo 12 Pump-approach flow pattern in Bay 4 with final fixes 31 Photo 13 Pump-approach flow pattern in Bay 4 with final fixes 31 Photo 14 Pump-approach flow pattern in Bay 4 with final fixes 32 Photo 15 Pump-approach flow pattern in Bay 4 with final fixes 32 Photo 16 Performance of horizontal grating in Bay 4 with final fixes 33 Photo 17 Model baffle blocks installed underneath the discharge flume

(seeing Bays 1 and 2) 33 Photo 18 Recommended discharge-flume outlet structure 34 Photo 19 Dye trace observed during the test simulating Unit-1 discharge at LWL 34 Photo 20 Dye trace near the discharge outlet during the test simulating Unit-1

discharge at HWL . 35 Photo 21 Dye trace in the downstream region for the same test as shown in

Photo 20 35 Photo 22 Dye trace near the discharge outlet during the test simulating Unit-2

discharge at LWL 36 Photo 23 Dye trace in the downstream region for the same test as shown in

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Photo 22 36

LIST OF FIGURES

page Figure 1 System diagram of the proposed helper-cooling tower project 37 Figure 2 Plan of the entire model with through-flow traveling screens 38 Figure 3 Detailed plan and section of the intake 39 Figure 4 Detailed section of the discharge flume 40 Figure 5 Plan and section of the pump bell 41 Figure 6 Orifice-meter calibration curve 42 Figure 7 Elbow-meter calibration curves 43 Figure 8 Calibration curve for the current meter 44 Figure 9 Classification of free-surface vortices 45 Figure 10 Plan of the entire model with dual-flow traveling screens 46 Figure 11 Plan and section of the intake with dual-flow traveling-screen frames 47 Figure 12 Sump velocity distributions in Run No.1AD 48 Figure 13 Sump velocity distributions in Run No.1ADM1 49 Figure 14 Sump velocity distributions in Run No.1ADM2 50 Figure 15 Sump velocity distributions in Run No.1AMD3 51 Figure 16 Sump velocity distributions in Run No.1ADM4 52 Figure 17 Recommended layouts of splitters and corner fillets 53 Figure 18 Recommended layout of the horizontal grating 54 Figure 19 Preliminary layout of baffle blocks for Bay 1 55 Figure 20 Final layout of baffle blocks for Bay 1 56

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Figure 21 Final layout of baffle blocks for Bay 2 57 Figure 22 Final layout of baffle blocks for Bay 3 58 Figure 23 Final layout of baffle blocks for Bay 4 59 Figure 24 Sump velocity distributions in Run No.1ADF . 60 Figure 25 Sump velocity distributions in Run No.2ADF 61 Figure 26 Sump velocity distributions in Run No.3ADF 62 Figure 27 Sump velocity distributions in Run No.4ADF 63 Figure 28 Sump velocity distributions in Run No.5ADF 64 Figure 29 Sump velocity distributions in Run No.6ADF 65 Figure 30 Sump velocity distributions in Run No.7ADF 66 Figure 31 Sump velocity distributions in Run No.8ADF 67 Figure 32 Sump velocity distributions in Run No.9ADF 68 Figure 33 Sump velocity distributions in Run No.10ADF 69 Figure 34 Sump velocity distributions in Run No.11ADF 70 Figure 35 Sump velocity distributions in Run No.12ADF, 13ADF, 14ADF,

and 15ADF 71 Figure 36 Pump-throat velocity distribution in Pump 1 in Run No.1AD 72 Figure 37 Pump-throat velocity distribution in Pump 2 in Run No.1AD 73 Figure 38 Pump-throat velocity distribution in Pump 3 in Run No.1AD 74 Figure 39 Pump-throat velocity distribution in pump 4 in Run No.1AD 75 Figure 40 Pump-throat velocity distribution in Pump 1 in Run No.1ADF 76 Figure 41 Pump-throat velocity distribution in Pump 2 in Run No.1ADF 77 Figure 42 Pump-throat velocity distribution in Pump 3 in Run No.1ADF 78

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Figure 43 Pump-throat velocity distribution in Pump 4 in Run No.1ADF 79 Figure 44 Recommended layout of baffle blocks for Bay 1 80 Figure 45 Recommended layout of baffle blocks for Bay 2 81 Figure 46 Recommended layout of baffle blocks for Bay 3 82 Figure 47 Recommended layout of baffle blocks for Bay 4 83 Figure 48 Sump velocity distributions in Bay 1 for Run Nos.1ADF1, 4ADF1,

7ADF1, and 12ADF1 84 Figure 49 Sump velocity distributions in Bay 2 for Run Nos.2ADF1, 9ADF1,

10ADF1, and 13ADF1 85 Figure 50 Sump velocity distributions in Bays 3 and 4 for Run Nos.14ADF1

and 15ADF1 86

Figure 51 Pump-throat velocity distribution in Pump 1 in Run No.1ADF1 87 Figure 52 Pump-throat velocity distribution in Pump 2 in Run No.1ADF1 88 Figure 53 Pump-throat velocity distribution in Pump 3 in Run No.1ADF1 89 Figure 54 Pump-throat velocity distribution in Pump 4 in Run No.1ADF1 90 Figure 55 Pump-throat velocity distribution in Pump 2 in Run No.13ADF1 91 Figure 56 Sump velocity distributions in Run No.1ADF1EXL 92 Figure 57 Sump velocity distributions in Run No.1ADF1EXH 93 Figure 58 Pump-throat velocity distribution in Pump 2 in Run No.1ADF1EXL 94 Figure 59 Recommended plan layout of the discharge-flume outlet structure 95 Figure 60 Detailed plan and section of the recommended discharge-flume

outlet structure and flow-turning vane layout 96

A HYDRAULIC MODEL STUDY OF THE PROPOSED PUMP-INTAKE AND DISCHARGE FLUME: FLORIDA POWER CORPORATION'S CRYSTAL

RIVER HELPER COOLING-TOWER PROJECT

I. INTRODUCTION A. Background. Florida Power Corporation's (FPC) Crystal River electric energy

complex is located in Crystal River, about 100 miles north of Tampa, Florida, and

consists of four coal-burning plants and one nuclear power plant. Units 1, 2, and 3 have

once-through circulating-water cooling systems. The proposed helper cooling-tower

project for Units 1, 2, and 3 is intended to reduce the warm-water temperature in the

discharge canal during warm months. The system, as sketched in figure 1, comprises a

pump-intake structure, four cooling towers, and two cooling-tower basin discharge

flumes. Approximately 52% of the total discharge-canal flow will be diverted through

the intake structure to the cooling towers located adjacent to the canal, and the cooled

water will be discharged through the two discharge flumes into the discharge canal,

where mixing of the two flows will take place. The pump-intake system utilizes four

vertical pumps to pump heated sea water from the Gulf of Mexico. The pumps are rated

at 383 cfs (171,500 gpm) each against a designed total dynamic head of 61 ft. Warm

water enters each bay through a trashrack at the intake entrance, passing through a dual-

flow (or so-called, double-entry, center-exit) traveling screen, and is pumped into a

common discharge header which can direct flow to either or both of the east or the west

cooling-tower pairs.

B. Scope of Study. Many of the large-scale vertical pumps installed in power plants and

various pumping stations have experienced some sort of vibration, impeller damage due

to local cavitation, excessive bearing wear, or loss of pumping efficiency, combinations

of which are considered to be caused primarily by undesirable pump-approach-flow

conditions in pump sumps, including nonuniform pump-approach-flow distributions,

insufficient pump-submergence depth, and inappropriate geometrical layout surrounding

the pump bells. These are known to produce prerotation, air-entraining free-surface

vortices, and boundary-attached subsurface vortices, respectively. Conventional fixes to

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resolve these problems include flow-straightening devices such as an array of deep vanes

or baffle blocks and/or a perforated plate to improve sump-flow distributions, floor- and

backwall-attached vortex splitters to avoid subsurface vortex formation, and horizontal

grating to suppress formation of free-surface vortices (Dicmas 1978; Nakato 1984, 1988,

and 1989; Sweeney et al., 1982; Tullis 1979).

In order to determine if the proposed intake-structure layout provides hydraulically

acceptable pump-approach flows to the individual pumps, and to determine if adequate

mixing between the cooled water discharging from the discharge flume and flow in the

discharge canal is achieved, a 1:10-scale geometrically undistorted, hydraulic model of

the Crystal River Units 1, 2, and 3 Helper Cooling-Tower Project intake and discharge

flume was built at the Iowa Institute of Hydraulic Research (IIHR), The University of

Iowa. Development of remedial measures for unsatisfactory performance of the proposed

pump-intake and discharge-flume structures, if found during the course of the study, was

the ultimate objective of this model investigation. The more specific, principal concerns

were as follows:

(1) the effect of the narrow, pump-sump cross section at the dual-flow traveling-

screen exit on pump-approach-flow velocity distribution in each sump;

(2) velocity distribution in each pump sump in the immediate vicinity of the pump

bell;

(3) pump-throat velocity distribution in each pump;

(4) formation of air-entraining, free-surface vortices at extremely low water levels;

(5) formation of floor-attached, backwall-attached, or sidewall-attached, subsurface

vortices;

(6) possibility of recirculation of the cooled water back into the intake structure; and,

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(7) mixing process of the cooled water in the discharge canal upon discharge into the

canal.

II. PUMP-INTAKE AND DISCHARGE-FLUME MODEL

A. General. The entire model was built at an undistorted geometrical scale of 1:10 and

installed in the Institute's Model Annex (see figure 2 for its plan). The originally

designed intake structure had through-flow traveling screens, as shown in figure 3.

However, this screen layout was soon replaced by the dual-flow traveling-screen

configuration, which will be discussed later. The as-designed discharge-flume layout in

which the flume flow enters the discharge canal at an angle of 45 degrees is shown in

figure 4. It should be pointed out that the entire model was built in mirror image of the

prototype configuration in order to fit the model within the available space in the building.

Therefore, any drawings presented in this report should be viewed as mirror images of

the prototype installations. The model included a portion of the discharge canal (see

Photo 1), approximately 220-ft wide and 700-ft long in prototype dimensions, the pump

sumps with detailed piers (see figure 3 and Photo 2), four pump-suction bells (see figure

5 and Photo 3a), portions of pump-suction lines, the common discharge header, and the

discharge flume (see Photo 4). The model basin was constructed primarily from fir

timber and plywood, and the basin surface was coated with fiberglass material for water-

proof purposes and painted using epoxy paint. The model pump sumps were provided

with a lucite window in each of two side walls and four sump backwalls. These windows

facilitated flow visualization and lighting.

Flow to the model was supplied through a 12-in. pipe connected to the 30-hp pump which

pumped water from the underground sump. The model water-supply line was connected

to a 12-in. diffuser pipe perforated with 1/2-in. orifices. The lateral distribution of flows

in the discharge canal was adjusted by altering the pattern of open orifices by means of

rubber plugs (a simple technique used with success at IIHR). Immediately downstream

from the diffuser, a baffle wall with a horse-hair screen stapled to it was installed to

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reduce flow turbulence. The four intake-pump flows were withdrawn from the model by

means of a 10-in. pump with a 7.5-hp motor (see Photo 5), with one half of the pumped

flow being routed to the Unit-1 cooling-tower discharge flume, and the other half to the

laboratory's pump sump (note that in the prototype this flow will be routed to the other

cooling tower). A calibrated orifice meter placed in the 12-in. supply line measured the

total discharge into the model, and four additional elbow meters, one installed at each

model suction line, measured the flow rate through each model pump bell. Flows into the

model and through the model suction lines were regulated by means of standard butterfly

valves installed in the water-supply pipe and the individual suction lines.

Each model pump bell was machine-formed to scale from transparent lucite (see figure 5

and Photo 3b), and was connected to the lucite suction line. The model pump bells were

fitted at their suction lines with vortimeters (four-blade, zero-pitch propeller supported by

low-friction pivoted shafts). The pump-throat section was fitted with ports through

which a 3/32-in. Prandtl-type pitot tube was inserted for velocity measurements. The

model suction lines were constructed such that velocity could be measured along each of

eight radii at 45-degree intervals.

B. Equipment and Test Procedure. The instrumentation which was used in the present

pump-intake study was as follows:

(1) Conventional orifice meters were used to measure the discharge into the main

model water-supply diffuser pipe, and that into the discharge flume. The meters

were calibrated in the lines in which they were installed using the IIHR's weighing

tank (for example, see figure 6 for the calibration curve obtained for the 10-in.

diameter orifice plate installed in the 12-in. water-supply pipe). The calibration

facility permits discharge calibration over the range from 1 gpm to 7.0 cfs,

approximately, to a relative accuracy of 0.01. Differential heads across the orifice

plates were measured by means of precision two-tube manometers manufactured

at IIHR;

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(2) Elbow meters were used to estimate flow rates passing through the suction lines

(see figure 7 for their calibration curves);

(3) A two-component, electro-magnetic flow meter manufactured by Montedoro-

Whitney Corporation (Model MVM-1, maximum error: 2%) was used to measure

velocities in the pump sumps. Vertical locations of the flow meter were

determined using a point gage which was fabricated at IIHR and equipped with

vernier scales with a resolution of 0.001 ft. The flow meter was calibrated in the

IIHR's 2-ft wide flume using a laser doppler anemometer. The calibration curve is

shown in figure 8;

(4) A 3/32-in. Prandtl-type pitot tube, attached to a precision zero-displacement

manometer with a resolution of 0.001 ft of water, was used to measure velocity

distributions at pump throats;

(5) A 1/2-in. wide, four-blade, zero-pitch vortimeter, which was supported by low-

friction pivoted shafts, was installed in each suction line to measure prerotation of

pump-approach flow, which served as a measure of the strength of prerotation in

the pump-column flow; and,

(6) Flow visualization was achieved by means of food dye injected through a wand

tipped with a hypodermic needle and placed at desired locations in the flow field.

Flow patterns were photographed and videotaped, and selected photos are

included herein.

The laboratory procedure followed in testing pump-intake flows involved, first, filling

slowly the model discharge canal slightly above the low water level by adjusting the

valve in the 12-in. main water-supply line, and purging off air by means of a shop

vacuum attached to an air vent in the 12-in. diameter pipe manifold which is connected to

both the 7.5-hp pump and the four model suction lines. In this manner, the 10-in. pump,

which pumped one half of the cooling water to the discharge flume, simulating operation

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of one pair of cooling towers, was able to be started. Once the suction pump was

activated, each intake pump discharge was set by adjusting the 8-in. line suction-pipe

butterfly valve. Second, the required water discharge to the discharge canal was

accurately set, and the model tailgate was adjusted to maintain the proper discharge-canal

water level. The proper flow rate to the discharge flume was set by adjusting the valve in

the dump line which simulated the discharge line to another cooling tower. This model

dump line discharged water into the underground water-storage sump in the building.

Fine adjustments of the pump-intake discharges, the discharge into the discharge flume,

and the water level in the discharge canal were repeatedly made to ensure proper model-

operating conditions. It required approximately 45 minutes to obtain stable model-

operating conditions.

The model was operated in accordance with the Froude-similarity law. Undistorted

geometric similarity requires that the ratio of all corresponding dimensions in model and

prototype be equal. Thus, all geometric length ratios are given by

Lr = Lm/Lp .............................................................................................................(1)

where Lr, Lm, and Lp are the length ratio, model length, and corresponding prototype

length, respectively. Flow processes involving a free surface, as is the case in this study,

are controlled predominantly by gravitational and inertial forces. Therefore, it is

important that the prototype-model ratio of gravity forces to inertial forces be preserved.

This requires that Froude number, F, be the same in model and prototype:

Fr = Fm/Fp = 1 .......................................................................................................(2)

where F = V/(gL)0.5 ..........................................................................................................(3)

where V is a characteristic flow velocity; g is the gravitational constant; and L is a

representative length. The scale ratios for velocity, discharge, and time resulting from (1),

(2), and (3) for Lr = 1/10 in the present case are

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Vr = Vm/Vp = Lr0.5 = 1/3.16 ..................................................................................(4)

Qr = Lr2 Lr

0.5 = Lr2.5 = 1/316.2 ………………………..……………...................(5)

Tr = Lr0.5 = 1/3.16 .................................................................................................(6)

The rotational flow indicator in the suction line is generally expressed in terms of the

angular velocity of the vortimeter tip and the average axial velocity. The swirl angle, θ,

is defined by

θ = tan-1(Vθ/Vz) ....................................................................................................(7)

where Vθ = 2πrω/60 = tangential velocity at the tip of the vortimeter blade; r = radius of

pump column; ω = angular velocity of vortimeter in rpm; and Vz = average axial velocity

of pump-column flow.

C. Criteria for Satisfactory Pump Operations. IIHR's experience with numerous

studies of this type has led to the following model criteria for satisfactory operations of

prototype pump installations:

(1) No detectable boundary-attached vortices extending into the pump bells;

(2) No free-surface vortices stronger than type 2, as shown in figure 9;

(3) No velocities measured at the pump suction line that vary by more than 10% from

the average of all local velocities measured in the cross section;

(4) No depth-averaged pump-bay intake velocities, measured approximately one-bay

width upstream from the pump bell, that deviate by more than 20% from the area-

averaged pump-bay average velocity over the central 75% of the bay width;

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(5) Vortimeter-tip velocity angles (swirl angles) no greater than 5 degrees; and,

(6) No detectable, large-scale, persistent "unsteadiness" or "waviness" in the pump-

bell approach flows; no indication of persistent large-scale turbulence; no flow

anomalies judged objectionable by investigators experienced with pump-intake

model tests.

III. PUMP-INTAKE TEST RESULTS

A. Description of Preliminary Model Screening Tests. The first phase of the

preliminary test program involved the conduct of screening tests to identify the test case

which produced the worst pump-bell inlet-flow conditions, as judged from vortimeter

speed and vortex formation as detected through flow visualization assisted by injection of

food dye into the flow. Fifteen possible pump-operating combinations, listed in table 1,

were examined at LWL (EL<->2'2"), because previous IIHR experience has shown that

vortex formation in the pump sump is more acute at lower water levels. Although the

original intake design utilized a through-flow traveling-screen scheme, it was replaced

with the dual-flow screen scheme in the early stages of the model testing program.

Therefore, the dual-flow traveling screens are called "as-designed" throughout this report.

A plan of the as-designed intake model with dual-flow screen-support frames is shown in

figure 10, and a detailed plan and a section of the sump-inlet section in the vicinity of the

dual-flow screen section of each pump bay are shown in figure 11 (see also Photo 6).

Note that the flow-turning vanes shown in figure 11 were not included in the original

design. For all test cases in the preliminary screening tests, the model discharge,

corresponding to the rated unit-pump discharge of 383 cfs (171,500 gpm) for the four-

pump operation at LWL (EL<->2'2"), was utilized. It should be pointed out that upon

completion of the screening tests, the following rated discharges were utilized to reflect

the correct pump-rating curves for the LWL operations: 402 cfs (180,330 gpm) for three-

pump operations, 414 cfs (186,000 gpm) for two-pump operations, and 421 cfs (189,000

gpm) for one-pump operations (see table 1). The results of vortimeter readings are

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summarized in table 2. Clockwise motion of the vortimeter (looking down) was defined

as positive, and counterclockwise, negative. The model vortimeter readings shown in

table 2 were obtained by averaging three, 2-minute long readings. All test cases showed

the high magnitude in prerotation defined in equation (7). In terms of the critical swirl

angle of 5 degrees, it is allowable to have about 16 rpm in model dimensions. No single

worst case was able to be easily determined. Therefore, it was decided to develop

corrective means using four pumps in operation in the model.

There were two primary mechanisms responsible for nonuniform pump-approach flow

distributions which resulted in rather high prerotation in each bay. First, the intake

structure was designed to withdraw, at a right angle to the discharge-canal axis,

approximately one half of the warm water flowing in the discharge canal, as shown in

figures 1 and 10. The discharge-canal flow was not able to turn abruptly 90 degrees

toward the intake because of the cross flow existing in the discharge canal (see Photo 7).

Therefore, each pump-intake flow had to enter the bay at an angle. This caused a flow-

separation problem in each bay at the intake entrance, producing laterally nonuniform

flow distributions within the sump. As in most right-angle intake structures, the

upstreammost bay (Bay 1 in this case: note that the four intake bays were numbered in

increasing order toward the downstream direction) experienced the severest flow

nonuniformity because flow had to enter the bay from an area downstream from the

intake. The severity of flow turning problems diminished gradually toward the

downstream bays. Second, each intake flow had to pass through the dual-flow screens

first, at a normal angle to the intake axis, and then to exit from the narrow opening

(approximately one-third of the bay width: see figure 11 and Photos 6 and 8) as a jet over

a 2.5-ft high boot section, separating from the entire boundary of the screen exit opening.

This flow separation produced large captive eddies, resulting in strong reverse currents

along the sidewalls as well as along the sump floor. The combination of these two

aspects (right-angle withdrawal with cross flow and dual-flow traveling screen) made the

pump-approach flow distributions extremely nonuniform, both vertically and laterally. It

is worth noting why vortimeter readings in Bay 1 were always negative under the as-

designed condition. As described earlier, discharge-canal flow had to enter Bay 1 at an

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angle directed toward the upstream direction, which resulted in much higher velocity

along the left sidewall of the bay after flow separation took place at the right pier nose.

This concentrated flow then exited from the narrow traveling-screen exit opening as a jet

directed toward the right sidewall, producing a general flow pattern of pump-approach

flow circulating around the pump column counterclockwise. This prerotation pattern

reflected on the sign of the vortimeter movement.

Because of the nonuniform distributions in pump-approach flows described above, both

sidewall-attached and backwall-attached subsurface vortices were observed in all bays.

Strong floor-attached vortices were also observed in all bays. Well-organized, air-

entraining vortices also appeared frequently, as shown in Photos 9 and 10. These free-

surface and subsurface vortices were found to behave in an extremely irregular manner.

In particular, vortices tended to be camera-shy and to disappear whenever the equipment

was ready for photographing. In general, it took from a few seconds to about five

minutes for them to reappear in the model, which corresponds to somewhere between

about 5 seconds to 16 minutes in prototype dimensions according to the time-scale

relationship given by equation (6).

In summary, preliminary model screening tests showed that there are three classic

problems in each bay, which are discussed at the very beginning of the first chapter:

nonuniform pump-approach flow distribution, free-surface vortices forming at rather low

sump water levels, and subsurface boundary-attached vortices forming at the sump floor

as well as along each backwall and sump sidewalls.

B. Description of Developmental Tests. The next phase of the program involved testing

of various fixes. Every effort was made to devise a simple, economical, and yet practical

scheme which would be easy to construct and maintain. In this phase of the study, close

communications were maintained between the client and IIHR to arrive at solutions

which were acceptable to the owner. Invaluable input was provided by Black & Veatch

Engineers-Architects.

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Before presenting the test results with the various fixes which were examined, the basic

hydraulic data collected with the as-built intake configuration are first presented. Pump-

approach-flow velocity distribution within each sump was measured by means of the

electro-magnetic flow meter at a cross section, 20-ft prototype distance upstream from

the backwall. At each bay, velocities were measured at three verticals which were spaced

equally across the sump. Along each vertical, velocities were measured at three locations,

3.5 ft (@ EL<->14'6"), 7.0 ft (@ EL<->11'0"), and 10.5 ft (@ EL<->7'6") in prototype

dimensions from the sump floor. Figure 12 shows velocity distributions measured in four

bays for Run No.1AD (Run No.1 listed in table 1 under As-Designed condition).

Velocities are shown in prototype dimensions. It should be pointed out that all

geometrical dimensions, including the sump width, height, velocity-measurement

locations, and water-surface level, are scaled proportionally in this figure as well as in

other similar figures involving pump-approach flow distributions. As can be seen in

figure 12, lateral velocity distributions are extremely nonuniform in all bays. Velocities

in the right half (looking downstream toward the pump) of Bay 1 are seen much higher

than those in the left half of the cross section, as described earlier. Higher velocities in

the right side of the sump produced a counterclockwise (by looking downward) pattern of

prerotational pump-approach flow in Bay 1. Flow distributions were opposite in Bays 2

and 3 in comparison with that in Bay 1. Bay 4 showed rather uniform velocity

distributions compared with the other three bays.

In order to improve nonuniform distribution in pump-approach flow in each sump,

various flow-turning devices were placed at different locations, primarily in Bay 1, and

their effectiveness in improving flow distributions was observed. First, a set of long

flow-turning vanes, as shown in figure 11, was placed in different locations within Bay 1

to test its effectiveness. However, it did not function as a device to re-distribute sump

flow across the bay. The second attempt involved utilization of a set of vertical baffle

blocks (12 in. by 12 in. square columns) to re-distribute nonuniform flow distributions.

Nineteen baffle blocks were staggered in Run Nos.1ADM1 and 1ADM2 (test conditions

were the same as Run No.1AD, but with Modifications M1 and M2) to improve velocity

distributions. The measured velocity distributions shown in figures 13 and 14 indicated

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the dramatic effect of these baffle blocks, as can be seen by comparing these profiles with

those shown in figure 12. Encouraged by the results in these two test cases, two more

cases involving seventeen blocks with guidewalls attached to the screen exit opening

were tested, as shown in figures 15 and 16. These did not seem to function effectively. It

should be noted that various types of perforated plates combined with deep flow-turning

bar racks were also tested, and they were found to improve significantly nonuniform

velocity distributions. A so-called, flow-area reduction method is generally used to

rectify nonuniform flow distributions by increasing head losses through perforated plates

or screens (Nakato 1988, 1989). Pressurized orifice flows issuing from individual

openings have a tendency to re-distribute laterally nonuniform pump-approach flows.

However, because of the maintenance problems posed by sea water, and the difficulty of

designing them for very deep and wide intake sumps, IIHR was asked by the client to

pursue the baffle-block scheme. According to this phase of the study, the baffle-block

layout shown in figure 13 showed the best promise in improving pump-approach flow

distributions. The final optimization phase of the baffle-block scheme will be described

in the following section.

The aim of the next developmental phase of this investigation was to eliminate boundary-

attached subsurface vortices in the vicinity of the pump bell by means of vortex splitters.

Several splitters were tested with floor corner fillets for their effectiveness. One of those

combinations which was found most effective is shown in figure 17. As can be seen in

Section C-C of this figure, a triangular-shaped floor splitter, 200-in. long and 35-in. high,

was designed to eliminate floor-attached vortices, and a 19-in. deep and 220-in. high

backwall splitter was developed to prohibit flow circulation around the pump column as

well as eliminating backwall-attached vortices. The apex of the backwall splitter is only

6 in. from the edge of the bellmouth. During this phase of study, weak sidewall-attached

vortices were also observed along both the left and right sidewalls. These were

eliminated by means of sidewall floor-corner fillets. Among the several fillet

configurations tested, those shown in figure 17 (Section D-D) were found to function

most effectively. Furthermore, a 35-in. high backwall floor-corner fillet, as shown in

figure 17 (Section B-B), was needed to eliminate any vortex activity around the sharp

13

backwall floor corner. These modifications made the pump-approach flow enter the bell

smoothly without producing any swirling motions, and eliminated practically all

subsurface vortices surrounding the pump bell.

In order to suppress air-entraining, free-surface vortices, such as the ones shown in

Photos 9 and 10, a horizontal grating, consisting of 6 in. by 6 in. grids, 3-in. deep, and

extending about 165 in. from the backwall, was suspended at EL<->7'0" (about 2 ft-6 in.

below Extreme LWL), on the basis of IIHR's previous experience (Nakato 1984, 1988,

1989). The layout of the grating is shown in figure 18. The proposed grating eliminated

entirely formation of free-surface vortices even when the sump water-surface elevation

was dropped to as low as EL<->6'0". It should be pointed out that the vortex splitters

employed in suppressing subsurface vortices had little effect on formation of free-surface

vortices. Photos 9 and 10, taken through the sidewall window in Bay 4, show fully-

developed, air-entraining, free-surface vortices with all the recommended splitters in

place.

The effectiveness of the vortex-suppressing components developed in this study can be

witnessed by a series of still photographs taken in Bay 4 during Run No.1ADF when four

pumps were withdrawing 383 cfs each at LWL as follows: Photo 11 shows streamlined

flow when food dye was introduced into flow immediately upstream from the bellmouth

at its level; Photo 12 shows smooth, non-vortexing flow extending from the floor level

(dye was injected on the nose of the floor splitter); Photo 13 shows straight flow near the

pump axis (dye was introduced along the right side of the floor splitter); Photo 14 shows

a pattern of non-vortexing smooth flow approaching from the backwall floor corner (see

the location of the wand tip in the photo); Photo 15 shows streamlined flow extending

from the floor (dye was introduced in the middle of the floor space between the floor

splitter and the right sidewall-corner fillet); and, finally, Photo 16 shows smooth

nonturbulent flow passing through the horizontal grating.

C. Presentation of Final Optimization Test Results. The primary purpose of this phase

of the study was to test all the fixes which were determined to be most effective during

14

the developmental phase described above under different pump-operating modes, listed

in table 1, and to adjust or optimize the fixes as needed. As stated earlier, the fixes were

developed under Run No.1 conditions with four pumps operating at the rated discharge of

383 cfs each, and they were developed primarily for Bay 1. The main target was to

adjust the arrangement of baffle blocks in individual bays so that they could function as

flow-straightening devices under any pump-operating conditions.

As can be seen in figure 13, the three-row baffle-block layout, positioned just upstream

from the discharge-flume wall, produced a much improved pump-approach velocity

distribution in Bay 1 in comparison with that under the as-designed condition (see figure

12 for velocity distribution in Bay 1). However, this block layout in Bay 1 was soon

found to be ineffective when Pump 2 was dormant, because the flow had to enter Bay 1 at

a much steeper angle. This resulted in much higher velocities along the right sidewall in

Bay 1. Therefore, attempts were made to block off part of the openings between the

front-row blocks, as exemplified in figure 19 for Bay 1. The block layout shown in

figure 19 functioned very well when Pump 2 was off (for example, in Run Nos.4, 7, and

11: see table 1 for the operating conditions). However, it produced unacceptable velocity

distributions for the other pump-operating combinations involving two- and three-pump

operations. Therefore, innumerable block combinations for each of the four bays were

tested in order to achieve the best block arrangements for all the possible pump

combinations.

The optimized baffle-block arrangements for Bays 1, 2, 3, and 4 are shown in figures 20

through 23, respectively. Note that the right side of the front-row baffles was blocked off

in Bay 1, the left side in Bay 2, and the left middle section in Bay 3. Bay 4 required only

two rows of equally-spaced baffle blocks because the inflow angle to this bay was not as

severe as in the other three bays. Three rows of blocks overcompensated the adjustment

required for Bay 4. The pump-approach velocity distributions measured at LWL (EL<-

>2'2") for the fifteen test cases listed in table 1 are shown in figures 24 through 35. The

letter "F" was affixed to each Run No. to identify the final phase of testing. As explained

previously, when Pump 2 was shut down, such as in Run Nos.4ADF, 7ADF, and 12ADF,

15

velocity distributions in Bay 1 were worse than those in Run No.1ADF. Velocity

distributions in Bay 2 were also not uniform when only two or three pumps were in

operation. Bays 3 and 4 produced, under any circumstances, quite uniformly distributed

pump-approach velocity distributions. Nonetheless, the most important fact to be

emphasized herein was that in spite of the degree of nonuniformity present in some of the

bays under certain pump-operating conditions, neither undesirable subsurface- nor free-

surface vortices were found with the final fixes presented in figures 20 through 23 for the

baffle blocks, as well as in figures 17 and 18 for the near-pump-bell fixes. It should also

be pointed out that the vortimeter readings for Run Nos.1ADF through 15ADF were all

within a few rpm or less, in model dimensions.

During both the developmental and the final test phases, detailed pump-throat velocity

measurements were made using a pitot tube for different operating conditions. Velocities

were measured at a cross section just above Station No.1 shown in figure 5. In each case,

the average velocity was first calculated, and individual velocities were normalized by

the mean value. Figures 36 through 39 show the distributions of the normalized

velocities measured under the as-designed conditions in Bays 1, 2, 3, and 4, respectively

(no fixes were present). According to these velocity profiles, the normalized velocities

along each concentric circle seem to be quite uniform. This does not mean that the

pump-throat velocity distribution is acceptably uniform under the as-built condition. In

fact, flow through each pump throat was extremely turbulent under the influence of both

nonuniform pump-approach-flow conditions and various vortices extended into the pump

bell. However, unfortunately, the pitot tube was not able to detect such local transient

flow conditions. It measured only mean quantities through pressure differences. Figures

40 through 43 show the velocity distributions measured in four bays in Run No.1ADF.

In these figures, it is hard to distinguish improvements in velocity distribution with the

final fixes. However, the maximum deviation within each concentric circle from the

cross-sectionally averaged, mean normalized velocity was within 2 to 3%, which is

excellent by any standards.

16

After completing all the tests with the proposed final fixes, IIHR was requested by the

client to check if the test results were still valid when the proposed baffle blocks were

moved slightly downstream, as shown in figures 44 through 47, so that the front-row

baffle-block face became flush with the discharge-flume wall. Photo 17 shows this

baffle-block arrangement (showing Bays 1 and 2). Therefore, several selected test runs

were made in each bay. Figure 48 shows the pump-approach flow distributions measured

in Bay 1 for four cases (Run Nos.1ADF1 (Q = 383 cfs), 4ADF1 (Q = 402 cfs), 7ADF1 (Q

= 414 cfs), 12ADF1 (Q = 421 cfs): note that the letter "1" was attached to "F" in Run Nos.

to identify the new baffle-block locations). Figure 49 shows similar results obtained in

Bay 2 for four different cases, and figure 50 in Bays 3 and 4 for Run Nos.14ADF1 and

15ADF1 (both are for the single-pump operating mode: Q = 421 cfs). As can be seen in

these figures, the pump-approach flow distributions were even slightly improved when

compared with those under the proposed final fixes. The pump-throat velocity

distributions were also measured in four bays for Run No.1ADF1 (Q = 383 cfs) and in

Bay 2 for Run No.13ADF1 (Q = 421 cfs), and they are plotted in figures 51 through 55.

In summary, no adverse effects were found after installing baffle blocks under the

discharge flume. Finally, the four-pump operating case was tested at both Extreme Low

Level (EL<->4'6") and Extreme High Level (EL<+>1'6"). The sump velocity

distributions for Run Nos.1ADF1EXL (Q = 383 cfs each) and 1ADF1EXH (Q = 383 cfs

each) are shown in figures 56 and 57, respectively. Under these extreme water levels, the

proposed baffle blocks functioned well. Figure 58 shows the excellent distribution of the

pump-throat velocity measured for Pump 2 for Run No.1ADF1EXL (Q = 383 cfs).

Although no data were collected, flow-visualization tests were conducted for Run

No.ADF1EXL with a pump discharge of 421 cfs (110% of the rated capacity) each in

order to make sure that no adverse effect would appear with an increased discharge.

Neither subsurface nor free-surface vortices were found in any of the four bays under this

condition.

The final aspect of the model testing was related to head losses across the proposed flow-

straightening devices of the baffle blocks as well as through the dual-flow screen

structure without modeled screens. Head losses were measured in Run No.1ADF1 by

17

means of a point gauge in Bay 3 which withdrew the rated discharge of 383 cfs at EL<-

>2'2". According to the measurements, the head loss due solely to baffle blocks was only

about 1.2 in. in prototype dimensions. This small head loss is attributable to low mean

velocity in the sump which is slightly greater than 1 ft/s. The head loss due solely to the

dual-flow screen structure, excluding screen losses, was about 6.8 in. in prototype

dimensions. As pointed out previously, the flow through the dual-flow screen must

change its direction twice, and exits at a high velocity from the narrow opening, resulting

in large head losses.

Because water-surface elevations in all the test cases reported herein were set in the

discharge canal, about 400 ft downstream from the center axis of the intake, additional

individual sump water levels were measured directly in the model for a different water-

level setting. First, the LWL (EL<->2'2") in the discharge canal was set at the upstream

end of the intake by adjusting the tail gate, and Run No.1ADF1 was run. The measured

water-surface elevations in Bays 1, 2, 3, and 4 were EL<->3'1", EL<->2'6", EL<->2'7",

and EL<->2'7", respectively. The water-surface elevation in the discharge canal was

found to drop about 4 in. in prototype dimensions across the intake due to the lateral

withdrawal of the intake flow. Similar measurements were taken for Run No.1ADFEXL

(four pumps in operation at EL<->4'6"), which yielded the following water-surface

elevations: EL<->6'0" in Bay 1, EL<->5'0" in Bay 2, EL<->4'4" in Bay 3, and EL<->4'5"

in Bay 4. Approximately as much as 18 in. of head loss would be expected in Bay 1

under the EXL water-level condition. This is due to the increased velocities through the

dual-flow screens as well as the baffle blocks (note that the head loss is proportional to

the square of the mean velocity). Because of this extremely low water level in Bay 1, the

proposed horizontal grating was designed to be installed at EL<-> 7'0". Even under this

severe condition, no vortices were observed in the model, and flow patterns through each

pump bell were found to be well streamlined.

IV. DISCHARGE-FLUME TEST RESULTS

The as-designed, rectangular discharge flume is 52-ft wide and extends downstream over

the intake structure (see figure 2). This flume was designed to discharge the cooled water

18

into the discharge canal at a discharge angle of 45 degrees through a 20-ft wide,

discharge outlet structure after dissipating flow energy by means of a free overfall, as

shown in figure 4. The outlet-channel floor elevation was designed to be at EL<->10'6"

which is the same bottom elevation as the discharge canal. Two sidewalls of this outlet

channel were designed to slope down, following the existing bank slope (see Section B-B

in figure 4).

The primary objective of this part of the investigation was to ascertain whether the

discharge-flume outlet structure functions as designed in achieving adequate mixing

between the flume discharge and the discharge-canal flow. During preliminary tests

under the test conditions for Run No.1AD (simulating the Unit-1 discharge: total canal

discharge: 2,929 cfs (1,315,000 gpm); pump-intake discharge: 1,530 cfs (687,000 gpm)

under the four-pump operation at LWL (EL<->2'2"); and the cross-flow discharge in the

canal: 1,399 cfs (628,000 gpm)), the canal cross flow passing over the sloping bank

section in the discharge canal was found to deflect the cooled-water flow immediately

toward the bank, resulting in very poor mixing of the two flows. It was also noticed that

there was no external force available to propel the discharge flow into the canal against

the canal cross flow under the as-designed flume-outlet layout. Because the flume

elevation was designed to be the same as that in the discharge canal and all the potential

energy was entirely dissipated through the free-overfall scheme, there was no head

available to force the discharge flow to penetrate into the canal. On the basis of these

observations, the client re-designed the flume-outlet structure, which included raising the

flume-floor elevation by 3 ft (EL<->7'6"), extending the two sidewalls vertically above

the water surface, and installing a vertical endwall within the doglegged flume-outlet

section. The endwall served as a flow-control device, producing head so as to make the

discharge flow issue as a high-velocity jet. Although these modifications significantly

improved mixing processes in the discharge canal, they were not sufficient. Under the

Run No.1AD flow conditions described above, the discharge flow was unable to reach

beyond the centerline of the discharge canal. Therefore, it was decided to modify the

plan layout of the outlet.

19

As shown in figure 59, the new layout utilizes a right-angle discharge mode. A detailed

plan and section of the discharge-flume outlet structure are shown in figure 60 and Photo

18. The optimized location of the endwall (about 15 ft from the bottom bank line) was

determined by means of a trial-and-error procedure, by injecting food dye in the

discharge and observing the range of the discharge-flow penetration into the canal cross

flow toward the other side of the bank. The final configuration devised in this study also

includes installation of three flow-turning vanes (about 10 ft high) in order to produce

uniformly distributed flow across the outlet flume. Without these vanes, the discharge

flow separated at the inner sidewall, and the majority of flow concentrated along the

outer sidewall when the flow turned the corner where the final, right-angle outlet

structure begins (see figure 60). It should be noted that all the tests conducted in this

phase of the study involved visual observations of flow patterns.

General flow patterns under several critical flow conditions were documented by means

of a videotape and still photographs. Photo 19 shows an aerial view of the dye trace

observed during the test which simulated the Unit-1 discharge at LWL (EL<->2'2").

Food dye was injected next to the right sidewall underneath the endwall. The total canal

discharge upstream from the intake was 2,929 cfs (1,315,000 gpm); the intake discharge

was 1,530 cfs (687,000 gpm: four pumps operating); and the canal cross-flow discharge

was 1,399 cfs (628,000 gpm). As can be seen from this photo, a part of the cooled-water

flow reached the other side of the canal bank. Photos 20 and 21 show the same case as

shown in Photo 19 except that the canal water-surface elevation was maintained at HWL

(EL<+>1'6"). Because of a much lower mean velocity in the cross flow due to the larger

flow depth in the canal, the cooled-water flow reached closer to the right bank than a

similar case with the lower canal depth. Photos 22 and 23 show the flow pattern obtained

during the test modeling the Unit-2 discharge with a canal water level set at LWL (EL<-

>2'2"). In this case, the cross flow was increased to 2,155 cfs (967,750 gpm) to simulate

the second discharge flume. In other words, the discharge from the Unit-1 flume was

added to the discharge-canal flow. Because of the higher cross-flow velocity in this case,

the cooled-water flow was deflected more by the cross flow as it entered the canal when

compared with the similar case tested for the Unit-1 discharge. However, the discharge

20

flow was observed to mix with the canal flow quite well in downstream sections (see

Photo 23). In summary, the recommended discharge-flume outlet structure whose

configuration is outlined in figure 60 demonstrated its satisfactory performance in the

model.

V. RECOMMENDATIONS

The final recommendations derived from the present study may be summarized as

follows:

1. In each bay, an array of baffle blocks should be installed immediately underneath

the discharge flume to rectify nonuniform pump-approach-flow distributions.

Their prototype dimensions and geometrical layout are shown in figures 44, 45, 46,

and 47, for Bays 1, 2, 3, and 4, respectively. Bay 4 requires only two rows of

baffle blocks, while the other three bays require three rows;

2. Both the floor and the backwall vortex splitters, as well as sidewall-corner fillets,

whose dimensions are shown in figure 17, should be installed in each bay to

eliminate boundary-attached subsurface vortices;

3. A horizontal grating, consisting of about 3-in. deep, 6-in. by 6-in. grids, should be

installed at about EL<->7'0" in each bay to suppress formation of free-surface

vortices which might form during very low sump-water levels. A detailed layout

of the grating is shown in figure 18; and,

4. The axis of the discharge-flume exit should be perpendicular to the discharge-

canal axis, as shown in figure 59, in order to achieve the maximum mixing process

between flow in the discharge canal and that from the discharge flume. Three 10-

ft tall flow-turning vanes, whose plan dimensions are shown in figure 60, should

be installed so that uniformity in the lateral velocity distribution can be achieved

within the discharge flume upstream from the endwall which produces a high-

21

velocity jet. The endwall should be located about 15 ft from the bottom line of the

discharge-canal bank, as shown in figure 60. The discharge flume should end with

a bed slope no greater than 45 degrees.

22

LIST OF REFERENCES

1. Dicmas, J.L., "Effect of intake structure modifications on the hydraulic performance of a mixed flow pump," Proceedings of the Joint ASCE/IAHR/AIHR/ASME Symposium on Design and Operation of Fluid Machinery, Colorado State University, Fort Collins, Colorado, June, 1978, pp.403-412.

2. Nakato, T., "Model investigation of intake-shoaling and pump-vibration

problems: Iowa Generation Council Bluffs Unit 3 Circulating-Water intake," IIHR Report No.283, Iowa Institute of Hydraulic Research, The University of Iowa, October, 1984.

3. Nakato, T., "Hydraulic-laboratory model studies of the circulating-water pump-

intake structure, Florida Power Corporation, Crystal River Units 4 and 5," IIHR Report No.320, Iowa Institute of Hydraulic Research, The University of Iowa, March, 1988.

4. Nakato, T., "A hydraulic model study of the circulating-water pump-intake

structure: Laguna Verde Nuclear Power Station Unit No. 1, Comision Federal De Electricidad (CFE)," IIHR Report No.330, Iowa Institute of Hydraulic Research, The University of Iowa, May 1989.

5. Sweeney, C.E., Elder, R.A., Hay, D., "Pump sump design experience: summary,"

Journal of the Hydraulics Division, ASCE, Vol.108, No.HY3, March, 1982, pp.361-377.

6. Tullis, P., "Modeling in design of pumping pits," Journal of the Hydraulics

Division, ASCE, Vol.105, No.HY9, September, 1979, pp.1053-1063.

23

1 2 3 41 X X X X 4-PUMP OPERATION2 X X X 3-PUMP OPERATION3 X X X "4 X X X "5 X X X "6 X X 2-PUMP OPERATION7 X X "8 X X "9 X X "

10 X X "11 X X "12 X 1-PUMP OPERATION13 X "14 X "15 X "

PUMP IDENTIFICATION OPERATING MODERUN NO.

NOTES:

1. X: pump in operation

2. Pump No.1 is located at the upstream end of the intake structure, and No.4 at the downstream end.

3. The rated pump discharges for the LWL (EL<->2'2") operations are as follows:

Four-pump operation: 383 cfs (171,500 gpm)/each Three-pump operations: 402 cfs (180,330 gpm)/each Two-pump operations: 414 cfs (186,000 gpm)/each One-pump operations: 421 cfs (189,000 gpm)/each

Table 1 Summary of possible pump-operating combinations

24

1 2 3 41 -24.5 -5.5 22.0 19.0 4-PUMP OPERATION2 -23.5 20.0 26.5 3-PUMP OPERATION3 -25.5 -5.0 21.5 "4 -31.0 16.0 18.5 "5 -25.0 27.0 4.0 "6 -38.0 -36.0 2-PUMP OPERATION7 -28.0 -21.0 22.0 "8 -37.5 "9 -41.5 -30.0 18.5 "

10 -30.5 -20.5 "11 -27.5 "12 -30.5 1-PUMP OPERATION13 -31.5 "14 -27.0 "15 27.0 "

RUN NO. PUMP IDENTIFICATION OPERATING MODE

NOTES:

1. Vortimeter readings (rpm) are in model dimensions. Prototype rpm's are 3.16 times smaller than model values (3.16 = SQRT(10))

2. Direction of vortimeter movement: clockwise positive and counterclockwise

negative (looking from the top).

3. Water level in the discharge canal was set at LWL (EL<->2'2").

Table 2 Summary of measured vortimeter speeds under the as-designed conditions

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96