To Study the Flow Characteristics of Hydraulic Jump Developed in Laboratory Flume

[FAISAL SARDAR] 2009-CIV-122

EXPERIMENT N0: 4 TO STUDY THE FLOW CHARACTERISTICS OF THEHYDROSTATIC JUMP DEVELOPED IN LAB F L U M E

OBJECTIVES :    

To physically achieve the hydraulic jump in lab flume. To measure the physical dimension of hydraulic jump. To calculate the energy losses through hydraulic jump/ To plot the water surface profile of the hydraulic jump for various discharges.

APPARATUS:  S6 Tilting or lab flume with automatic flow arrangement and slop adjusting scale.2.  Hook Gauge

RELATED THEORY HYDRAULIC JUMP : The rise of water level which takes place due to transformation of super critical flow to the sub critical flow is termed as hydraulic jump. 1

2

Dam d2

yc d1 1

2

In The Figure At Sec-1 D1 < Yc So Super – Critical Flow And At Sec-2 D1 < Yc So Sub– Critical Flow

[FAISAL SARDAR] 2009-CIV-122

EXPRESSION FOR DEPTH OF HYDRAULIC JUMP :

EXPRESSION FOR LOSS OF ENERGY DUE TO HYDRAULIC JUMP : 1

2

hL

W.L Dam d2

yc d1 1

2

LENGTH OF HYDRAULIC JUMP: Distance between section where one section is taken just before the hydraulic jump and second section is taken after the hydraulic jump. Length = 5-7 times of depth

[FAISAL SARDAR] 2009-CIV-122

LOCATION OF HYDRAULIC JUMP : Location of jump depends upon d2 and y2 y2 = Normal depth of flow on downstream side. d2 =conjugate depyh of hydraulic jump

√

d2 = Case No. 1 ( y2 > d2 )  

Strength of jump is the amount of energy dissipated due to structure. Jump is submerged in water so it is a weak jump. 2

U/S

y2

d2

Dam

D/S

2

Case No. 2 ( d2 = y2 )  Strength of jump is the amount of energy dissipated due to structure.  Energy dissipated in this jump is more than in Case No. 1 so it has greater strength.

2

U/S Dam

y2

d2 2

D/S

[FAISAL SARDAR] 2009-CIV-122

Case No. 3 ( y2 < d2 ) 2

U/S

y2 D/S

d2

Dam Floor

2

 Depth Of Floor Is Less So It Will Damage The Floor  Dangerous .  Cause Crossion/Scouvring

NOTE : so ideal case will be case no. 2 as structure is i. Safe ii. Sufficient energy dissipated If Case No. 2 does not fit accordingly to the conditions then Case No 1 will be use as it has less energy dissipation but it is safe but Case No. 3 will never be adopted as it is unsafe and by adopting this Case will resulting defoliation of the floor

CLASSIFICATION OF H.J: classification on the basis of U/S frauds number / approach number.

1) FN    

Undular Jump Water Surface Show Undulation Very Weak Jump

2) FN  

1.1-1.2

1.7-2.5

Peak hydraulic jump Weak jump

[FAISAL SARDAR] 2009-CIV-122

 

Series of small roller develop on the surface of jump but d/s water remain smooth Energy losses low

3) FN

2.5-4.5

 Ooscilating hydraulic jump  There is oscilating jet emtering the jump bottom to the surface and back again with no periodicity .



Each oscilation produce a large wave of irregular periodwhich very commonly cannals can travel for miles doing unlimited damages to earth bank and riprags



This tYpe of jump is avoided.

4) FN

4.5-9

 

Steady hydraulic jump



Jump is well balanced and performance is at best

Downstream extremety of the surface roller and the point at which the high velocity jet tend to release the Flow occurs at the practically the same vertical section .

 Energy losses ( 45-70%) 5) FN  Strong hydraulic jump  In this jump a high velocity jet of water grabs intermedent slugs of water rolling down the front surface of the jump generating waves downstream and a rough surface can prevail.

 Jump action is rough but effective  Energy losses may reach 85% PRACTICAL APPLICATIONS OF HYDRAULIC JUMP 1. 2.

To dissipate the energy of water flowing over the hydraulic structure and thus prevent scouring on the downstream side. To recover the head or raise the water level on downstream side of the hydraulic structure and thus to maintain high water level in the channel for irrigation or other water distribution purposes.

[FAISAL SARDAR] 2009-CIV-122 3.

To increase the weight on apron and thus reduce the uplift pressure under the structure by raising the water depth on apron. Apron: A layer of flexible material

D/S U/S Drain water causing uplift pressure

4.

Dam Floor

To Mix The Chemicals For Water Purification E.T.C

PROCEDURE: 1. 2. 3. 4. 5. 6.

Fix one particular value of slope. Change the discharge every new reading. Measure the depth of flow at various locations. Measure the horizontal distance at each section. Repeat the same procedure for various discharges. Plot the data in the form of Tables and Graphs.

Apron

[FAISAL SARDAR] 2009-CIV-122

OBSERVATION & CALCULATION : DEPTH OF FLOW U/S OF H.J (m)

DEPTH OF FLOW D/S OF H.J (m)

yc

VELOCITY OF FLOW U/S OF H.J

VELOCITY OF FLOW D/S OF H.J

FROUD'S NO. BEFORE JUMP FN1

DEPTH OF H.J (d2-d1)

LENGTH OF H.J

ENERGY LOSS IN H.J

m

m

m

0.224

0.102

0.512

0.094

4.420

0.266

0.110

0.548

0.128

0.319

2.802

0.277

0.107

0.533

0.077

1.578

0.288

2.915

0.228

0.134

0.668

0.122

0.0669

1.589

0.311

2.749

0.238

0.140

0.701

0.116

0.0741

1.694

0.330

2.799

0.240

0.154

0.772

0.129

Q

q

m3/sec

m3/sec/m

d1

d2

d3

davj

d1

d2

d3

davj

m

m/sec

m/sec

1

0.009338

0.0311

0.023

0.023

0.023

0.023

0.121

0.125

0.129

0.125

0.0462

1.361

0.248

2.874

2

0.011659

0.0389

0.019

0.020

0.021

0.020

0.127

0.130

0.131

0.129

0.0536

1.953

0.300

3

0.012958

0.0432

0.028

0.030

0.029

0.029

0.133

0.136

0.138

0.135

0.0575

1.493

4

0.014139

0.0471

0.029

0.029

0.032

0.030

0.163

0.163

0.165

0.164

0.0610

5

0.016244

0.0541

0.034

0.034

0.034

0.034

0.173

0.173

0.177

0.174

6

0.018969

0.0632

0.037

0.038

0.037

0.037

0.188

0.193

0.195

0.192

SR.

SR #

Q

HORIZONTAL DISTANCES

m3/sec

FROUDS NO. AFTER JUMP FN2

UP STREAM

DOWNS TREAM

x1

x2

x3

x1

x2

x3

1

0.009338

5.7

5.75

5.82

7.76

7.85

8

2

0.011659

5.7

5.75

5.82

7.76

7.85

8

3

0.012958

5.82

5.93

6.05

7.85

7.95

8

4

0.014139

5.8

5.85

5.94

8.55

8.6

8.65

5

0.016244

5.9

5.95

6.13

8.7

8.75

8.8

6

0.018969

6.1

6.15

6.3

8.9

8.95

9

[FAISAL SARDAR] 2009-CIV-122

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