CER65JFR51.November 1965.Includes bibliographical references.Prepared for Northern Colorado Water Conservancy District Loveland, Colorado

Ruff, James F.

English

Ruff, James F., author

Colorado State University, Engineering Research Center, Civil Engineering Department, publisher

Mountain Scholar (Digital Collections of Colorado and Wyoming)

T=0\.. 9t:O tA1 CE:. c.ee-1os-s1 e,-,.'l-- HYDRAULIC lVIODE r, STUDY HANSEN SUPPLY CANAL STi t, LING BASIN .AND PARSHALL FLUME NORTHERN COLORADO WATER CONSERVANCY DISTRICT Civil Engineering Department Engineering research Center Colorado S t ate University Fort Collins, Colorado Nov e mber , 1965 CER65JF'R51. FINAL REPORT OF HYDRAULIC MODEL STUDY HANSEN SUPPLY CANAL STILLING BASIN AND PARSHALL FLUME Prepared for Northern Colorado Water Conservancy District Loveland, Colorado November 1965 by J. F . Ruff Colorado State University Engineering Research Center Civil Engineering Department Fort Collins, Colorado CER65JFR51 PREFACE The Engineering Research Ce nter at Colorado State University is located between two lakes, Horse -tooth Reservoir of the Colorado-Bi g Thompson pro -ject and College Lake . The laboratories of t he C e n-ter are strategically located to utilize the high head , 250 feet, available from the reservoir and t he stor-age capacity of the lake . The Center is the focal point for research and graduate e ducation. There are four principal parts to the Center: the offices for staff and graduate students, the hydraulics laboratory, the fluid dynamics laboratory and t he outdoor hydraulics-hydrology laboratory. Inc luded in the research activities of the Center are fluid m ec hanics, hydraulics, hydrology, ground-wate r , soil mechanics, hydrobiology, geomorphology and e nvironme ntal e ngineering. The Center includes well - e quipped machine and woodwork shops. All research facilities of the Center are cons:::-ucted on site and for this model study, necessary metal work and carpentry were done b y personnel in the shops. The shop pe rsonnel are particularly well -experienced in the art and skill of model construction. Gra teful acknowledgment is hereby ex -pressed by the v,riter to Dr. D. B . Simons, Profes-sor and Associate Dean, College of Enginee ring, and Mr. S. Karaki, Associate Professor, De partment of Civil Engineering for their administrative and tech-nical assistance, t o personnel in the shops for their contributions in solving model construction problems, and to others cor..tributing to the model study and preparation of this report. The writer wishes to express his appreciation for the coope ration of the staff of the Northern Colorado Water Conservancy District in providing assistance and helpful sugges-tions during the model tests . LIST OF FIGURES LIST OF TABLES SUMMARY INTRODUCTION TABLE OF CONTENTS General Description of the Project Description of the Parshall Flume Scope of Mode l Study Model Scale and Criteria MODEL Model Const ruction Model Tests and Results Dentated End Sill Baffle Blocks . . . . . Baffle Block B . . . . . Underpass Wave Suppressors CONCLUSIONS AND RECOM:.vIENDATIONS ii iii iv 3 3 3 3 3 3 3 13 LIST OF F IGURES Figure - Details of structures 2 - Schematic drawing of model 3 - Photograph of completed model 4 - Dentated end sill 5 - Baffle block locations 6(a) - Water surface in Parshall flume - no modifications 6(b) - Water surfac e in Parshall flume with five additional baffl e blocks installed on basin floor 7 8 9 10 11(a) 11(b) 12(a) 12(b) 1 3 - Baffle block B - Water surface at the Parshall flume with block B installed - Suppressor location and modifications - Wave reduction at Parshall flume - Water surface in Parshall flume Q=7 10cfs - Water surface in Parshall flume with suppressor A installed - Water surface in Parshall flume Q = 1120 cfs .. . .. . Water surface in Parshall flume with suppressor A installed - Recommended underpass wave suppressor ii Q = 1280 cfs Q= 7 10cfs Q 11 20cfs 2 4 4 5 6 7 7 8 8 9 11 11 11 12 12 14 LIST OF TABLES Table Page I Model prototype scale ratios II Wave heights in Parshall flum e in feet 1 0 iii SUMMARY This report describes a hydraulic model study of the stilling basin and Parshall flum e for the Hansen Supply Canal. The structure was modifie d to include an underpass wave suppre ssor. iv Air vents are provided to relieve air releases and water surface disturbances at the underpass exit . The model construction, tests, conclusions and recommendations are described in this r eport. INTRODUCTION Ge neral Desc ription of the Project The Hansen Supply Canal supplies water from Horsetooth Reservoir to the Cache La Poudre Rive r . The canal has a capacity of 15 00 cfs . Approximately one quarter of a mile downstream from the Greeley Waterworks Dam, located at the mouth of Poudre Can7on, the canal bifurcates . From this point, the l e ft b ranch, known as the Hansen Extension Canal, continues up the south bank of the river, crosses the river in a siphon and discharges into the Poudre Valley Canal. T he right branc h of the bifurcation enters a stilling basin, passes through a 20 - foot Parshall flume and discharges into the river . Desc ription of the Parshall F lume Detail plan and profile of the bifurcation, still -ing basin, Parshall flum e , and appurtenant works are shown in Fig . 1. Radial gates automatically control the water depth in the canal and the discharge into the branches of the bifurcation. The stilling basin con -sists of a 23 - feet long parabolic curved chute approach to the basin, and a hydraulic jump basin 58 - feet long. Chute and floor blocks are provided in the basin to assist in the formation and stabilization of the jump. The chute and basin are 18 feet wide to a point 18-feet 5-inches downstream from the intersec -tion of the chute and the basin floor. At this point the walls flare to 30 feet wide at the e ntrance to the Parshall flume. The flume has a 20 - fe e t crest length. Downstream from the flume another stilling basin is provided to dissipate the ene rgy before the water dis -charges into t he river. Scope of Model Study The purpose of the model study is to investi-gate hydraulic performance of stilling basin and Parshall flum e for the range of d ischarge from 500 to 1400 cfs. The specific objectives sought in this model study are: 1. Dete rmine through visual observations, photographs, and moving pictures the flow characteristics through the stilling basin and Par shall flume for t he dis -charge range . 2. Determine a m eans of attenuating the waves gene rated within the stilling basin before they pass through the Parshall flume . · Model Sc ale and Criteria The objective of the model is to develop flows kinematically and dynamically similar to the proto -type. Since the hydraulic jump, open channe l flow and surface waves are dependent upon gravity pre -dominately, the Froude criterion was chosen to e stablish the geometric scale . A model - prototype relationship of 1: 10 was determined t o be the most feasible from an analysis of scale ratios based upon a model size required for an accurate ;epresentation of the flow conditions, available facilities , and economy of cost. Table I contains a list of some of the characteristic model-prototype ratios based upon the selected scale. TABLE I MODEL PROTOTYPE SCALE RATIOS Scale Ratio Absolute Magnitude Function of Numerical Parameter the length Ratio Prototype Model Length L 1: 1 0 10 ft. 1 ft . r (L )2 1 : 1 00 1 00 ft. z 1 ft. z Area r Velocity (L ) 1 /2 1:3. 162 1 o fps 3. 162 fps r Discharge (L )5/2 1:31 6. 2 1000 c f s 3. 162 cfs r 1 Left and right, as used in this report, refer to the observer's left and right looking downstream PLAN N EL ~239.98""' EL ~231.31 SECTION A-A FIG. DETAIL OF STRUCTURE MODEL Model Construction Dimensions of the model facilities and the arrangement are given in Fig. 2. A photograph of the completed mode l is shown in Fig. 3. Water for the model was supplied through the 36-inch pipeline from Ho:-setooth Reservoir. The discharge was controlled by a Rockwell Hypresphere valve. A calibrated Venturi meter in the supply line was used to measure the discharge. Plywood was the main construction material for the model. The transition between the lined canal and the bifurcation was formed in concrete . Model Tests and Results The model study was concerned with the pre-vention or attenuation of surface waves in the Par-shall flume. The waves are generated by the hy-draulic jump formed in the stilling basin. The short reach between the stilling basin and the Par-shall flume is not of a sufficient length for the waves to be attenuated by friction and gravity. Many methods to reduce or eliminate these waves were attempted. The more significant tests are discussed he re inafte r. Dentated End Sill A dentated end sill 3-feet 2-inches high with 6 dentations was installed at the downstream end of the stilling basin. A sketch of the dentated end sill is shown in Fig. 4. The sill was then moved up-stream at 5-feet intervals. No noticeable change in the wave height or frequency was observed with the sill installed at any position. Baffle Blocks Five additional baffle blocks of the same size as the existing blocks were installed on the basin floor. The relative location of the additional blocks is shown in Fig. 5. Figure 6 shows the water sur-face at the Parshall flume for the original conditions and fol.' , he conditions with five additional baffle blocks. Some reduction in the wave magnitude could be observed with the added blocks installed. The reduction was not sufficient to constitute a solution to the problem. The extra baffle blocks were removed. Baffle Block B The three original baffle blocks we re re -placed with a rr_odified baffle block (hereafter refer -red to as block B). Block B was 4-1 /2 feet i n height with fillets at the top and bottom of the upstream face. The dimensions of block Bare given in Fig. 7. The inc:-eased cross section of block B caused the hydraulic jump to move slightly upstream. Block B did not appear to have any significant effect on the reduction of the waves generated by the hy-draulic jump. The water surface at the Parshall flume with block B installed is shown in Fig. 8 . Waves are 1. 3 to 1. 5 feet in height at the staff gage. Underpass Wave Suppressors An underpass wave suppressor was designed and installed in the model. The design base1 upon data developed by the Bureau of Reclamation in -dicated a suppressor 21 feet in length (hereafter referred to as suppressor A). Suppressor A was placed at several locations within the flume to deter-mine the location at which the suppressor was most effective. Place·ment of the suppressor too near the upstream end of the stilling basin allowed the high velocity jet to pass through the suppressor and generate waves 0. 3 to O. 5 feet in height at a dis -charge of 700 cfs. Placement of the suppressor too near the Parshall flume crest was not satisfactory. If the suppressor was submerged sufficiently to be effec-tive for a large range of discharges, the increased head on the suppressor created higher velocity flows through the Parshall flume. Reducing the submergence and thus reduc ing the head on the sup-pressor required that the discharge be 850 cfs or greater before the suppressor became effective. The location at which the suppressor is most effective is shown in Fig. 9. The roof of the underpass is 7 feet above the stilling basin floor. Also shown in Fig. 9 are the suppressor modifica-tions which were tested. The modifications are designated as suppressors C, D, and E. 2Peterka, A. J., Hydraulic Design ~ Stilling Basins and Energy Dissipators. Engineering Monograph No. 25, U. S. Bureau of Reclamation, revised July 1963, pp 48-56. 3 >-------------'•~•~o~e~·-----------r-----225~0_· ___ ~ PLAN ("Al VE FROM~ RESERVOIR Pl 10" tp PIPE ~ENTUR/ METER ! , n~ , ,, ,,,,,,,JL ,m,mm=,,_l)=::;;;,;:B:,'.";,;;;;;;;;;;;;;;j L, ; m;mt,,::5:::ir;.:;: O<JTLET CHANNEL It_ PROFILE Figure 2. Sche matic drawing of model. Figure 3. Photograph of the completed model. 4 FIG_ 4 END SILL 0 C, <D 14'-6" '<0 -.'.. I '- " 1s'-o" [[] [[] PLAN [] - -[[] [J 15'-o" se'-o" PROFILE FIG. 5 BAFFLE BLOCK LOCATIONS --- ·-- · --· 37'- o" Figure 6(a) Water surface in Parshall flume -no modifications . Figure 6(b) Water surface in Parshall flume with five additional baffle blocks installed on basin floor. 7 I a ' l'l I 3' - o" 3'-o" 1·-,____~___, <D 1--------------11-~ Figure 7. Baffle block B. Figure 8 . Water surface at t he Parshall flum e with block B installed. Q = 12 80 , 8 <D ' -.,. SUPPRESSOR C SUPPRESSOR E I I l....ff I I [] I I I I I D I I I I 0 [] .I J_j_ ~" I F - rT D a, I 0 - I I - I [] I I 0 I I "' I I ~ I I . I I I SUPPRE SSO R A SUPPRESSOR D P L A N a'- o" 21' - o" s'-o" Jo- I I I s'-o" I I I 0 I ~----- (]> I 0 I I -,_ I PROFILE FIG. 9 SUPPRESSOR LOCATIONS ANO MODIFICATIONS Suppressors, A, C, D and E are e qually effective in reducing wave heights for discharges up to about 750 cfs . Figure 1 O shows the percent of wave height reductions found at different dis -charges for each suppressor. Figure 10 indicates that the suppressors A, C , D and E are satis-factory in reducing waves over the specified dis-charge range. The magnitude of the waves without suppression and with suppressors A, C, D and E installed are given in Table II. Figures 11 and 12 show the water surface at the Parshall flume for discharges of 710 cfs and 1120 cfs respectively, without and with suppressor A installed. Additional tests were made with baffle block B replac ing the original baffle blocks and suppres -sor A installed. No measurable difference in wave heights :'rom those given in Table II for suppressor A were observed dur ing these tests. TABLE II Wave Heights at Parshall Flume in Feet-Prototype Discharge in cfs 710 1120 1360 Wave height before suppression o. 75 1. 0 1. 5 Wave height with suppressor A o. 06 o. 11 0.25 Wave height with suppressor C o. 06 o. 08 o. 15 Wave height with suppressor D o. 06 O. 1 D o. 20 Wave height with suppressor E o. 06 o. 1 0 o. 18 10 100 I-I <..? SUPPRESSOR c"' w I w 90 > <( 3 lL 0 z 0 I-u -------- -----~ E-=-------~ ------------'-~ ::::> 0 w et: 0 80 a' 600 700 800 900 1000 1100 1200 1300 1400 DISCH AR GE IN cfs PROTOTYPE FIG. 10 WAVE REDUCTION AT PARSHALL FLUME Figure 11( a} Water surface in Parshall flume -Q= 7 10 cfs . Figure 11(b) Water surface in Parshall flume with suppressor A installed -Q = 710 cfs . 11 Figure 12(a) Water surface in Parshall flume -Q = 1120 cfs . Figure 12(b) Water surface in Parahall flume with suppressor A installed -Q = 1120 cfs . 12 co::-.rCLUSIONS AND RECOMMENDATIONS Ope ration of the stilling basin and P arshall flume without any modifications results in waves up to 1-1 /2 feet in height passing over the crest of the flume . Additional baffle bl ocks or larger baffle bl ocks do :10t significantly reduce the wave amplitude . Flow conditions through the P arshall flume were made satisfactor y by the addition of an under-pass wave suppressor. Fou r suppressors were tested; each performed satisfactorily . Wave heights were reduced 83. 3 % to 90 % at a discharge of 1 360 cfs . A wave r eduction of 83. 3 % a t 1 360 cfs was con-sidered satisfactory. 13 Suppressor A produced the 83 . 3 % reduc tion in wave height. It is recommended and will effect some economy in the cost of materials and cons truc -tion over the othe r suppressors. Observation of the prototype in operation show s considerable air en-t rainment for discharges above 5 00 cfs . To provid e some relie f for .:cir rel ease and resulting surface turbulence at t he underpass exit, air vents should be provide d in t he roof of the underpass s uppre ssor. The air vents should be approximate l y 4-inches in diameter. The location and orientation of t he recomme1Jded s ·.1ppressor and air ve nts are shown in Fig . 1 3 . LL1/ [[] -' □ -0 -0 N [J I -~ ~ □ [D ~ P L A N FLOW PROFILE FIG. 13 RECOMMENDED UNDERPASS o· 6"¥1' ' ~ + I -N t @, -0 + .,. ' ""ic= ~+--~ ~ -+ _, N -,-~ + -1-.r // AIR VENTS 4" I.D _, I'--. = I -N N WAVE o" I'--_, .,. I N lB" 0 -,!_ SUPPRESSOR -0 I -0'> 0 I -0 "' 

Final report of hydraulic model study: Hansen Supply Canal, stilling basin and Parshall flume

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Final report of hydraulic model study : Hansen Supply Canal, stilling basin and Parshall flume

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