Energy dissipation - irrigation engineering

ENERGY DISSIPATION IS AN IMPORTANT TERM USED IN THE ENGINEERING. ESPECIALLY CIVIL ENGINEERING. THIS IS USEFUL IN THE FIELD OF IRRIGATION

1. ENERGY DISSIPATION IRRIGATION ENGINEERING

2. -:CREATED BY:- KAVIN RAVAL 141080106026 -:SUBMITED TO:- PROF. HEMALI DESAI CIVIL DEPARTMENT ACET

3. CONTENT ENERGY DISSIPATION BELOW SPILLWAY HYDRAULIC JUMP STILLING BASINS BUCKET TYPE ENERGY DISSIPATION PLUNGE POOLS

4. ENERGY DISSIPATION BELOW SPILLWAY CHAPTER -1

5. ENERGY DISSIPATION BELOW SPILLWAY Water flowing over a spillway acquires a lot of kinetic energy because of the conversion of the potential energy into kinetic energy. If the water flowing with such a velocity is discharged into kinetic energy. If the water flowing with such a high velocity is discharged into river it will scour the river bed. If the scour is not properly controlled, it may extend backward and may endanger the spillway and the dam. In order to protect the channel bed against scour, the kinetic energy of the water should be dissipated before it is discharged into the d/s channel. For the dissipation of the excessive kinetic energy of water, the following two methods are commonly adopted. 1. B y developing a hydraulic jump 2. By using different types of buckets

6. HYDRAULIC JUMP CHAPTER - 2

7. HYDRAULIC JUMP Hydraulic jump is the sudden rise of water that takes place when the flow changes from supercritical flow state to the subcritical state. When a stream of water moving with a high velocity and low depth strikes another stream of water moving with low velocity and high depth, a sudden rise in the surface of water place. This phenomenon is called hydraulic jump. This is generally accompanied by a large scale turbulence, dissipating most of the kinetic energy of supercritical flow. Such a phenomenon may occur in a canal below a regulating sluice, at the bottom of the spillway, or at a place where a steep channel slope turns flat.

8. HYDRAULIC JUMP

9. HYDRAULIC JUMP It may be noted that the depth before the jump is always less than the depth after the jump. The depth before the jump is always less than the depth after the jump is called the initial depth(y1) and the depth after the jump is called the sequent depth(y2) . In the specific energy diagram, the specific energy is minimum at point C. this depth of water in the channel, corresponding to the minimum specific energy ( at point C ) is known as critical depth.

10. HYDRAULIC JUMP Where y c = critical depth q = discharge per unit width (meter cube/second) = Q/b g = 9.81 meter/second square From the static energy curve, If y = y c …critical flow If y 1 < y c …supercritical flow If y 2 > y c …subcritical flow

11. HYDRAULIC JUMP FORMATION For hydraulic jump to be developed in a horizontal rectangular channel , the following equation must be classified. For a given discharge intensity over a spillway, the depth y 1 is equal to q/v 1 and v 1 is determined by the drop H 1 as

12. HYDRAULIC JUMP FORMATION

13. HYDRAULIC JUMP FORMATION JUMP HEIGHT CURVE(J.H.C.) y’ 2 for different discharges, the tail water depth is found by actual gauge discharge observations and by hydraulic computations. The post jump depths( y 2 ) for all those discharges , are also computed from equation. If a graph is now plotted between q and y 2 , the curve is known as jump height curve(J.H.C.) or y 2 curve. JUMP WATER CURVE (J.W.C.) The actual tail water depth ( y’2) corresponding to any discharge intensity q will however depend on the hydraulic condition of the river channel on the downstream side. The values of y’2 corresponding to different

14. HYDRAULIC JUMP FORMATION

15. Relative P osition Of J.H.C. A nd T.W.C.

16. Simple Horizontal Apron

17. Sloping apron below the bed

18. Sloping Apron Above The Bed

19. Sloping apron combined with stilling basin

20. Sloping Apron Partly Above And Partly Below The River Bed

21. Sloping Apron Partly Above And Partly Below The Ground Level

22. STILLING BASINS CHAPTER - 3

23. STILLING BASINS Stilling basins are external energy dissipators placed at the outlet of a culvert, chute or rundown. These basins are characterized by some combination of chute blocks, baffle blocks and sills designed to trigger a hydraulic jump in combination with a required tail water condition. With the required tail water, velocity leaving a properly designed stilling basin is equal to the velocity in the receiving channel. While various stilling basin designs ODOT practice is to use the St. Anthony Falls (SAF) stilling basin, which can operate over a range of approach flow Froude numbers from 1.7 to 17

24. TYPES OF STILLING BASINS [A] U.S.B.R. Stilling basin 1. Type – 1 Basin 2. Type – 2 Basin 3. Type – 3 Basin [B] Indian Standard Basin 1. Horizontal Apron Type -1 2. Horizontal Apron Type -2 3. Sloping Apron Type -3 4. Sloping Apron Type -4

25. U.S.B.R. Stilling basin

26. U.S.S.R. Type -1 Stilling Basin

27. U.S.S.R. Type -2 Stilling Basin

28. U.S.S.R. Type -3 Stilling Basin

29. Indian Standard Stilling Basin

30. I.S. Type -1 Basin

31. I.S. Type -2 Basin

32. I.S. Type -3 and Type -4 Basin

33. BUCKET TYPE ENERGY DISSIPATION CHAPTER - 4

34. BUCKET TYPE ENERGY DISSIPATION PLAY VIDEO

35. BUCKET TYPE ENERGY DISSIPATION Types of bucket type energy dissipation. 1. Solid roller bucket 2. slotted roller bucket 3. ski jump bucket

36. Roller Bucket

37. Solid Roller Bucket Energy Dissipater

38. Slotted Roller Bucket

39. Ski-Jump Bucket

40. Ski Jump B ucket

41. PLUNGE POOLS CHAPTER - 5

42. Plunge Pools Plunge pool is an energy dissipater structure constructed below water fall or rapids. In case of high supercritical flow, swirling of water or formation of eddies takes place and it is not possible to dissipate the energy by hydraulic jump type stilling basin. In such cases energy can be dissipated the energy by plunge pools.

43. Plunge Pools Plunge pool can develop as the result of : -> scour from spillway and bridge abutments -> jet issued from ski-jump bucket type energy dissipater -> jet issued from gated spillway Plunge pool is constructed in high dam structure. It is not feasible in case of low dam structure as it is uneconomical. Plunge pool scour involves a significant risk with trajectory of spillway may cause structural undermining at the foot of a dam.

44. Plunge Pools The plunge pool scour depends upon the following factors 1. Jet velocity 2. Jet shape 3. Air content of the jet 4. Level of tail water 5. Velocity of upstream flow 6. Gradation of sediment

45. Plunge Pools

46. THANK YOU