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Modification of the Hydraulic Jump by Submerged Jets

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Modification of the Hydraulic Jump by Submerged Jets Scholars' Mine Masters Theses Student Theses and Dissertations 1966 Modification of the hydraulic jump by submerged jets Edward Leon Tharp Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Civil Engineering Commons Department: Recommended Citation Tharp, Edward Leon, "Modification of the hydraulic jump by submerged jets" (1966). Masters Theses. 5775. https://scholarsmine.mst.edu/masters_theses/5775 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. MODIFICATION OF THE HYDRAULIC JUMP BY SUBMERGED JETS BY EDWARD LEON THARP A THESIS submitted to the faculty of the UNIVERSITY OF MISSOURI AT ROLLA in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN CIVIL ENGINEERING Rolla, Missouri 1965 Approved by ii ABSTRACT Tests were performed in order to determine the effect of submerged jets injecting water into the base of the hydraulic jump. The jump was studied in terms of the fol l owing properties: specific energy of the flow leaving the hydraulic jump, length of the hydraulic jump, tailwater depth, and wave formation properties. These properties for the hydraulic jump with submerged jets were compared to the natural hydraulic jump. Results of the tests indicate that: submerged jets at any angle tested tend to decrease the specific energy of the water leaving the jump and are more effective than the impulse-momentum principle indicates, submerged jets may be as effective as baffle piers in re­ ducing the length of the jump, and submerged jets at any angle tend to decrease the required tailwater depth of the hydraulic jump . iii ACKNOWLEDGMENTS The author wishes to express his appreciation to Professor Paul R. Munger of the Civil Engineering Department for his constant guidance and council in the preparation of this thesis . The author is also grateful to other members of the Civil Engineering Staff and the Computer Center Personnel for their help in interpreting the test results. iv TABLE OF CONTENTS PAGE ABSTRACT • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • i i ACKN OOLE OOME 'N'r • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • i i i LIST OF FIGURES • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . v LIST OF TABLES • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • vi N0}-fE NCI..AT'UR.E • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • vi i I. IN'I'RODUCTI ON ••••••••••• •••• ••••••• •••••• ••••• ••• • •• ••••••••• •• 1 II. LITERATURE REVIEW ••••••••••••••••••••••••••••••••••.•••••••••• 3 III. TESTING EQUIPMENT. 8 IV. TESTING PROCEDURE •••••••• • •••••• • ••••••••• ••••••••••• • •••••••• 12 v. DISCUSSION OF RESULTS •••••••••••••••••••••••••••••••••••• • •••• 17 VI. CONCLUSIONS ••••••••••••••••• • ••••••••••••••••••••.•••••••••••• 31 VII. REC~NDATIONS ••••••••••••••• • •• •••• • •• •• •• •••• •••••••••••••• 32 BI BLIOORA.PliY. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 3 VITA •••••• •• •••• • •• •• •• • . ................ ........................ 34 v LIST OF FIGURES FIGURE PAGE 1 SIDE VIEW OF TESTING APPARATUS. ..... .. .................... 9 2 ISOMETRIC OF TESTING APPARATUS. ............... .... .... .. 10 3 TEST FLlJl.fE . • • • • • • . • • • • • . • • • • . • • • • • • • . • • • • • • • • • • • • • • . • • • 11 4 RATIO OF TAILWATER DEPTH TO ENTERING DEPTH VERSUS FROUDE NlJMBER • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 18 5 EXIT SPECIFIC ENERGY VERSUS FROUDE NlJMBER.. ......... .... 19 6 RATI O OF FLOW THROUGH THE JETS TO FLOW OVER THE SPILLWAY VERSUS FROUDE NlJMBER. .... ............ .. ................ 20 7 ACTUAL AND THEORETI CAL SPECIFIC ENERGY OF WATER LEAVING THE JUMP VERSUS FROUDE NlJMBER... ........... .... ... 23 8 RATIO OF LENGTH OF JUMP TO ENTERING DEPTH VERSUS FROUDE N1Jl.IBER • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • 2 5 9 RATIO OF WAVE HEIGHT TO ENTERING DEPTH VERSUS FROUDE NlJMBER . • • . • . • • . • . • • • • . • • . • • . • • . • . • . • • . • . • . • . 30 vi LIST OF TABLES TABLE PAGE I INTERPRETATION OF TEST RESULTS.. ...... ........ .. .... 27 vii NOMENCLATURE The symbols are defined as they first appear in the text but are given here in alphabetical order for convenience. D Diameter of the jets in feet 0 Depth of water entering the stilling basin in feet Tailwater depth of the hydraulic jump in feet Specific energy of the water entering the stilling basin in feet Specific energy of the water leaving the hydraulic jump in feet Froude number of the water entering the stilling basin Acceleration of gravity in feet per second per second H Head on the spillway crest in feet Length of the hydraulic jump in feet Flowrate through the four jets in cubic feet per second Flowrate over the spillway in cubic feet per second Velocity of the water entering the stilling basin in feet per second Velocity of the water leaving the stilling basin in feet per second Wave height in feet g Angle between the copper tubes and the horizontal in degrees, measured in the upstream direction. I. INTRODUCTION The hydraulic jump is a very useful and reliable phenomenon in open channel flow . Its primary purpose is to reduce or eliminate erosion at the discharge end of a stilling basin. This is accomplished by dissipating much of the kinetic energy of the high-velocity stream entering the stilling basin. The high-velocity stream is broken into two components as it enters the hydraulic jump: the principal s tream, and the surface roller. Both of these components help dissipate some of the energy; however, the surface roller seems to be the most effective. Therefore, any method of increasing the amount of flow going to the surface roller should have an effect on the amount of energy dissipated by the jump. Common methods of accomplishing this are the use of baffle piers, end sills, and chute blocks. A few laboratory studies have been made to determine the feasi­ bility of using submerged jets to aid in energy dissipation, and to determine what effects they might have on the other properties of the hydraulic jump. Most of these studies have been conducted with the jets flush with the floor of the s tilling basin. If the tubes delivering water to the jump protruded through the f loor of the basin, it is logical that they should have a more significant effect due to the action of the jets in breaking up the principal stream in the hydraulic jump, as well as the baffle pier action of the tubes. Also, the angle at which the tubes deliver flow into the hydraulic jump should be a factor in determining the effect on the properties of the jump. This investigation has been undertaken to determine what effect the tubes protruding through the floor of the stilling basin will have 2 on the jump, as well as the effect of variation of the angle at which the jets deliver water t o t he jump. The effect on the jump will be judged by the t ailwat er depth, length of jump , the wave formati on properties of the jump, and the exit specific energy of the jump. 3 II . LI TERATURE REVIEW During the past several years, there has probably been more work done in connection with the hydraulic jump than any other phase of hydraulics . Most of this work falls into two distinct phases: the hydraulic jump as it occurs naturally, and methods of altering the form of the hydraulic jump . Hydraul ic jump studies require the establishment of basic, mathematical fluid flow relationships that must exist between various elements of the hydraulic jump . These rel ationships are then verified experimentally in the laboratory. I t is generally accepted that the impulse-momentum principle can be applied to the vertical e l ements of the jump . The relationships for the horizontal elements of the hydraulic jump are not as easy to establish. It was not until 1932 when Boris 1 A. Bakhmeteff and Arthur E. Matzke made an extensive study of the horizontal elements that the basic knowledge was acquired. These two men made significant contributions to the existing knowledge of the hydraulic jump . Firs t, they showed conclusively that the Froude number was the significant parameter for dynamic similarity. This dimension- less number was developed by the laws of dimensional analysis and shows that in open channel flow, gravity forces are the contr olling factors. Since the Froude number is dimensionless , it will apply equally well to either the mode l or the prototype. Second, they plotted accurate profiles of t he hydraulic jump at various Froude numbers. Third, they gave a rather accurate definition of the end point of the hydraulic jump as well as accurate measurements of the length. 4 2 A. J. Peterka has since made extensive studies of the horizontal elements of the hydraulic jump. From these studies, he was able to show that results obtained by Bakhmeteff and Matzke were not universally acceptable because the six inch flume, with which they made their
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