Lab Manual (Hydraulics Engineering)

HYDRAULICS ENGINEERING LAB MANUAL

T ABLE OF CONTENTS

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Experiment # 01 …………………………………………………………………….2 …………………………………………………………………….2 TO DETERMINE MANNING’S ROUGHNESS COEFFICIENT “n” AND CHEZY’S CO -EFFICIENT “C”

IN A LABORTARY FLUME 

Experiment # 02 ……………………………………………………………………11 TO INVESTIGATE THE RELATIONSHIP BETWEEN SPECIFIC ENERGY (SE) AND DEPTH OF FLOW(Y) IN A LABORATORY FLUM

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Experiment # 03 ……………………………………………………………..........16 ……………………………………………………………..........16 To study the flow characteristics over the hump or weir in a rectangular channel

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Experiment # 04 …………………………………………………………………...25 …………………………………………………………………...25 TO STUDY THE FLOW CHARACTERISTICS OF HYDRAULIC JUMP DEVELOPED IN LAB FLUME

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EXPERIMENT NO. 1 TO DETERMINE MANNING’S ROUGHNESS COEFFICIENT “n” AND CHEZY’S CO-EFFICIENT “C” IN A LABORTARY FLUME. OBJECTIVE: To study the variation in “n” with respect to discharge. To study changes in “c” with respect to discharge. To manipulate/investigate relation b/w: n” and “c”. To learn the procedure of determining “n” and “c” of any existing channel.

APPARATUS: S6 glass sided Tilting lab flume with manometric flow arrangement and slope adjusting scale. Point gauge (For measuring measuring depth of channel) channel)

RELATED THEORY: FLUME Open channel generally supported on or above the ground. UNIFORM FLOW: A uniform flow is one in which flow parameters and channel parameters remain same with respect to

distance b/w two sections. NON-UNIFORM FLOW: A non-uniform flow is one in which flow parameters and channel parameters not remain same with

respect to distance b/w two sections. STEADY FLOW: A steady flow is one in which the conditions (velocity, pressure and cross-section) may differ from point to point but DO NOT change with time. UNSTEADY FLOW: If at any point in the fluid, the conditions change with time, the flow is described as unsteady . (In practice there are always slight variations in velocity and pressure, but if the average values are constant, the flow is considered steady . STEADY UNIFORMM FLOW: Conditions do not change with position in the stream or with time. An example is the flow of water in a pipe of constant diameter at constant velocity. STEADY NON-UNIFORMM FLOW: Conditions change from point to point in the stream but do not change with time. An example is flow in a tapering pipe with constant velocity at the inlet - velocity will change as you move along the length of the pipe toward the exit.

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EXPERIMENT NO. 1 TO DETERMINE MANNING’S ROUGHNESS COEFFICIENT “n” AND CHEZY’S CO-EFFICIENT “C” IN A LABORTARY FLUME. OBJECTIVE: To study the variation in “n” with respect to discharge. To study changes in “c” with respect to discharge. To manipulate/investigate relation b/w: n” and “c”. To learn the procedure of determining “n” and “c” of any existing channel.

APPARATUS: S6 glass sided Tilting lab flume with manometric flow arrangement and slope adjusting scale. Point gauge (For measuring measuring depth of channel) channel)

RELATED THEORY: FLUME Open channel generally supported on or above the ground. UNIFORM FLOW: A uniform flow is one in which flow parameters and channel parameters remain same with respect to

distance b/w two sections. NON-UNIFORM FLOW: A non-uniform flow is one in which flow parameters and channel parameters not remain same with

respect to distance b/w two sections. STEADY FLOW: A steady flow is one in which the conditions (velocity, pressure and cross-section) may differ from point to point but DO NOT change with time. UNSTEADY FLOW: If at any point in the fluid, the conditions change with time, the flow is described as unsteady . (In practice there are always slight variations in velocity and pressure, but if the average values are constant, the flow is considered steady . STEADY UNIFORMM FLOW: Conditions do not change with position in the stream or with time. An example is the flow of water in a pipe of constant diameter at constant velocity. STEADY NON-UNIFORMM FLOW: Conditions change from point to point in the stream but do not change with time. An example is flow in a tapering pipe with constant velocity at the inlet - velocity will change as you move along the length of the pipe toward the exit.

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HYDRAULICS ENGINEERING LAB MANUAL STEADY UNIFORMM FLOW: At a given instant in time the conditions at every point are the same, but will change with time. An example is a pipe of constant diameter connected to a pump pumping at a constant rate which is then switched off. UNSTEADY NON-UNIFORMM FLOW: Every condition of the flow may change from point to point and with time at every point. For example waves in a channel .

MANNINGS ROUGNESS FORMULA The Manning formula states:

Where: V is the cross-sectional average velocity (L/T; (L/T; ft/s, m/s) k

is a conversion factor of 1.486 (ft/m) 1/3 for U.S. customary units and 1 in SI Units.

n

is the Manning coefficient (T/L1/3; s/m1/3)

Rh is the hydraulic radius (L; ft, m) S

is the slope of the water surface or the linear hydraulic head loss (L/L) ( S = h f /L)

Manning formula is used to estimate flow in open channel situations where it is not practical to construct a weir or flume to measure flow with greater accuracy. The friction coefficients across weirs and orifices are less subjective than n along a natural (earthen, stone or vegetated) channel reach. Cross sectional area, as well as n' , will likely vary along a natural channel. Accordingly, more error is expected in predicting flow by assuming a Manning's n, than by measuring flow across a constructed weirs, flumes or orifices. HYDRAULICS RADIUS:

The hydraulic radius is a measure of channel flow efficiency.

Where: Rh is the hydraulic radius, A is the cross sectional area of flow , P is wetted perimeter .

The greater the hydraulic radius, the greater the efficiency of the channel and the less likely the river is to flood. For channels of a given width, the hydraulic radius is greater for the deeper channels. The hydraulic radius is not half the hydraulic diameter as the name may suggest. It is a function of the shape of the pipe, channel, or river in which the water is flowing. In wide rectangular channels, the

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HYDRAULICS ENGINEERING LAB MANUAL hydraulic radius is approximated by the flow depth. The measure of a channel's efficiency (its ability to move water and sediment) is used by water engineers to assess the channel's capacity.

CHEZY’S FORMULA: Chezy formula can be used to calculate mean flow velocity in conduits and is expressed as

v = c (R S)

1/2

Where v = mean velocity (m/s, ft/s) c = the Chezy roughness and conduit coefficient R = hydraulic radius of the conduit (m, ft) S = slope of the conduit (m/m, ft/ft)

PROCEDURE: Measure Channel (Flume) width. Adjust the suitable slope. Fill the S-6 tilting flume up to some depth. Note down the readings of differential manometer and see the corresponding discharge from the discharge chart. Note down the depth of flow at different points. (e.g. 2m,4m,6m) Calculate the Co- efficient “C” and “n” accordingly by the given formulas.

PRECAUTIONS: Take manometric reading only when flow is steady. The height should not be measured near the joints or at points where there is turbulence in flume. The height measuring needle must be adjusted precisely. The tip of the needle must be just touching the water surface while taking observations.

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HYDRAULICS ENGINEERING LAB MANUAL Determination of Slope of Energy Line:

For Q= 0.00894 m³/s 0.2 0.18 0.16 ) 0.14 m ( e n i L 0.12 y g r e 0.1 n E f o 0.08 h t p e D0.06

0.04 0.02 0 0

1

2

3

4 Distance (m)

5

6

7

For Q= 0. 01200m³/s 0.2 0.18 0.16 ) m ( e n i L y g r e n E f o h t p e D

0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0

1

2

3

4

5

6

7

Distance (m)

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For Q= 0.01600 m³/s 0.2 0.18 0.16 ) m ( e n i L y g r e n E f o h t p e D

0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0

1

2

3

4

5

6

7

Distance (m)

For Q= 0.01833 m³/s 0.2 0.18 0.16 ) m ( e 0.14 n i L y g r 0.12 e n E f 0.1 o h t p 0.08 e D 0.06 0.04 0.02 0 0

1

2

3

4

5

6

7

Distance (m)

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For Q= 0.01918 m³/s 0.2 0.18 0.16 ) m ( e 0.14 n i L y g r 0.12 e n E f 0.1 o h t p e 0.08 D 0.06 0.04 0.02 0 0

1

2

3

4

5

6

7

Distance (m)

For Q= 0.020390 m³/s 0.2 0.18 ) m ( e n i L y g r e n E f o h t p e D

0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0

7

1

2

3 Distance (m)

4

5

6

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HYDRAULICS ENGINEERING LAB MANUAL Determination of Manning’s and Chezy’s Coefficient:

Bed Slope So

Q (m³/sec)

1

0.002

2 3 4 5 6

0.002 0.002 0.002 0.002 0.002

Sr. No

y= Depth Of Flow (mm)

Area Of flow A=(b x y) m²

Wetted Perimeter P= b + 2y (m)

Hydraulic Radius R=A/P (m)

Flow Velocity V= Q/A (m/sec)

Slope Of Energy Line S

Manning's Roughness Coefficient

y1

y2

y3

yavg

0.00894

55

59

60

58.000

0.0174

0.416

0.0418

0.514

0.0006523

0.0104

0.0059

56.188

98.389

0.012 0.016 0.01833 0.01918 0.02039

72 79 84 84 92

73 81 83 87 92

60 79 81 85 85

68.333 79.667 82.667 85.333 89.667

0.0205 0.0239 0.0248 0.0256 0.0269

0.437 0.459 0.465 0.471 0.479

0.0469 0.0520 0.0533 0.0544 0.0561

0.585 0.669 0.739 0.749 0.758

0.0012705 0.0005000 0.0002416 0.0002500 0.0005573

0.0098 0.0092 0.0085 0.0085 0.0086

0.0078 0.0046 0.0029 0.0030 0.0045

60.395 65.609 71.574 71.827 71.551

75.777 131.218 205.934 203.156 135.546

Graph b/w Discharge and Chezy’s Coefficient; 0.025

0.02

0.015 ) s / ³ m ( Q 0.01

0.005

0 40.000

45.000

50.000

55.000

60.000

65.000

70.000

75.000

Chezys Coefficient

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HYDRAULICS ENGINEERING LAB MANUAL Graph b/w Discharge and Manning ’s Coefficient; 0.025

0.02

) s / ³ m ( Q

0.015

0.01

0.005

n1

n2

Chezy's Coefficient

C1

C2

HYDRAULICS ENGINEERING LAB MANUAL Graph b/w Discharge and Manning ’s Coefficient; 0.025

0.02

) s / ³ m ( Q

0.015

0.01

0.005

0 0.0060

0.0065

0.0070

0.0075

0.0080

0.0085

0.0090

0.0095

0.0100

0.0105

0.0110

Manning's Coefficient (n)

Graph b/w Chazy’s Coefficient and Manning ’s Coefficient; 0.0120

0.0100 ) n ( t n e i c i f f e o C s ' g n i n n a M

0.0080

0.0060

0.0040

0.0020

0.0000 50.000

55.000

60.000

65.000

70.000

75.000

Chezy Coefficient,C

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HYDRAULICS ENGINEERING LAB MANUAL RESULTS: Value of Chezy’s Co -efficient increases with increase in discharge. Manning’s Co-efficient decreases with increase in discharge. There is Inverse Relation b/w Manning’s Co-efficient and Chezy’s Co-efficient.

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EXPERIMENT#02 TO INVESTIGATE THE RELATIONSHIP BETWEEN SPECIFIC ENERGY (SE) AND DEPTH OF FLOW(Y) IN A LABORATORY FLUME OBJECTIVES: i)

To study the variations in specific energy as a function of depth of flow for a given discharge in a lab flume.

ii)

To validate the theories of E-Y diagram( S.E and Depth) diagrams

APPARATUS: Tilting lab flume with manometric flow arrangement and slope adjusting scale. Hook gauge

RELATED THEROY: FLUME:

It is a channel supported above the ground level. SPECIFIC ENERGY: S.E if the total energy per unit weight measured relative to the channel’s bed and mathematically,

Where E = S.E of the per unit weight Y= depth of flow V2/2g = kinetic head or velocity head

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HYDRAULICS ENGINEERING LAB MANUAL When slopes are involves,

For mild slopes,

SPECIFIC ENERGY CURVE: It is the plot which shows the variations in S.E as a function of Depth of flow.

CRITICAL DEPTH: It is the depth of flow in the channel at which specific energy is minimum. Mathematically

FROUD’s NUMBER: It is the ratio of inertial forces to the gravitational forces. Mathematically it is:

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HYDRAULICS ENGINEERING LAB MANUAL CRITICAL FLOW: It is the flow corresponding to the critical depth with Froud’s Number = 1

CRITICAL VELOCITY:

Velocity corresponding to critical depth . SUB-CRITICAL FLOW: It is the flow with larger depths and less flow velocities or flow at which Froud’s Number is les than 1 .

SUPER CRITICAL FLOW: It is the flow corresponding to the lesser depths and larger flow velocities. And flow will be called as super critical flow for Froud’s Number

ALTERNATE DEPTHS: For the value of the specific energy other than at the critical point for a constant discharge, there are

two water depths. i)

One is greater than critical depths

ii)

Other is Less than critical depths

These two depths for a given specific energy are termed as alternate Depths .

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HYDRAULICS ENGINEERING LAB MANUAL PROCEDURE: 1. Maintain the constant discharge in open channel 2. For one particular value of flow, find out the water depths at the different locations and calculate the average depth of flow. 3. Calculate the specific energy using this relation: 4. Repeat this by varying the value of slopes. 5. Draw E –y curves 6. Find out the critical depths and E

min

7.


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HYDRAULICS ENGINEERING LAB MANUAL OBSERVATION &CALCULATION: WIDTH OF FLUME = Sr# 1 2 3 4 5 6

SLOPE 0 1 : 40 1 : 60 1 : 100 1 : 200 1 : 500

0.3 m

Discharge (m³/s) 0.012646 0.012646 0.012646 0.012646 0.012646 0.012646

DEPTH OF FLOW (m) Y1 0.0814 0.031 0.037 0.041 0.059 0.064

Y2 0.078 0.026 0.031 0.037 0.043 0.0669

Y3 0.0725 0.027 0.033 0.035 0.047 0.0647

Yavg 0.0773 0.0280 0.0337 0.0377 0.0497 0.0652

Velocity (m/s) 0.5453 1.5055 1.2521 1.1191 0.8487 0.6465

V²/2g

(m) 0.0278 0.0767 0.0638 0.0570 0.0433 0.0330

SPECIFIC ENERGY 0.1051 0.1047 0.0975 0.0947 0.0929 0.0982

E~Y DIAGRAM (Specific Energy Curve): 0.09 0.08 E=Y Curve

0.07

E~Y

0.06 )0.05 m ( Y , h t0.04 p e D 0.03

SUB CRITICAL FLOW

VC² /2g

YC

SUPER CRITICAL FLOW

0.02 0.01 0 0

0.02

0.04

Emin

0.06 0.08 Specific Energy,E (m)

0.1

0.12

0.14

RESULTS: Yc= 0.048 m Emin= 0.092m Flow below 0.048 m is super critical. Flow above 0.048 m is sub critical.

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EXPERIMENT # 03 TO STUDY THE FLOW CHARACTERISTICS OVER THE HUMP OR WEIR IN A RECTANGULAR CHANNEL OBJECTIVE To study the variation of flow with the introduction of different types of weirs in the flume.

APPARATUS 

S6 tilting flume apparatus which consists of Orifice Differential manometer Large chamber to study flow Controlling meter to vary slope. Hook gauge/point gauge to measure the depth



Broad crested weirs Rounded corner weir Sharp corner weir

RELATED THEORY HUMP Stream lined construction over the bed of a channel is called hump. OR The raised bed of the channel at a certain location is called as hump. WEIR It is the streamlined wall or structure constructed across a river or a stream at a suitable location. It is commonly used to raise the water level at a river or stream to divert the required amount of water into an off taking canal. Weirs can be gated or ungated. Gated weir is called as BARRAGE FLOW OVER WEIR OR HUMP

a) SUB CRITICAL FLOW Consider a horizontal, frictionless rectangular channel of width B carrying a discharge Q at depth y 1. Let the flow be subcritical. At section 2, a smooth hump of height ΔZ is built on the floor. Since there are no energy losses between sections 1 and 2, construction of a hump causes the specific energy at section to decrease by ΔZ. Thus the specific energies at sections 1 and 2 are,

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E 2 = E1 - ∆ Z

Channel transition with a hump Since the flow is subcritical, the water surface will drop due to a decrease in the specific energy. In above Fig the water surface which was at P at section 1 will come down to point R at section 2. The depth y2 will be give by,

b) SUPERCRITICAL FLOW If Y1 is in the supercritical flow regime, Fig below shows that the depth of flow increases due to the reduction of specific energy. Point P` corresponds to y 1 and point R` to depth at the section 2. Up to the critical depth, y 2 increases to reach y c at ΔZ = ΔZmax. For ΔZ > ΔZmax , the depth over the hump y 2 = yc will remain constant and the upstream depth

y1

will change. It will decrease to have a higher specific energy

E1`by increasing velocity V 1.

Specific energy diagram

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HYDRAULICS ENGINEERING LAB MANUAL EFFECT OF HUMP HEIGHT ON THE DEPTH OF FLOW: Height of hump is less than critical hump height then there will be sub critical flow over the hump, downstream of the hump and upstream of the hump. Depth of flow over the hump will decrease by a certain amount as there is a slight depression in the water. Further increase in the height of hump will create more depression of water surface over the hump until finally the depth becomes equals to the critical depth. When the hump height will be equal to the critical depth then there will be critical flow over the hump, sub critical on the upstream side and super critical just downstream of the hump. If the hump is made still higher, critical depth will maintain over the hump and depth on upstream side will be increased. This phenomenon is referred to as damming action. Critical Hump Height is the minimum hump height that can cause the critical depth over the hump is called as critical hump height.

CASE 1

When Z < << Zc and y2 >>> yc

The flow conditions will be sub critical Upstream level increases Over hump y2 > yc At downstream depth is recovered after a long distance

CASE 2

When Z = Z c Upstream level increases Over hump y2 = yc

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HYDRAULICS ENGINEERING LAB MANUAL CASE 3

When Z > Zc Afflux on upstream side (damming action) y1 > y3 and y2 = yc At this stage E1 = y1 + v12/2g + afflux

DAMMING ACTION: It is the sudden increase of the water depth at upstream side due to increase in hump height.

PROCEDURE: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Fix the slope of the flume Introduce a round corner wide crested weir in the flume at certain location Set the discharge in the flume having certain value. Note depth of flow at upstream side of hump, over the hump and downstream side of hump at certain point. Repeat steps 2-4 for the other discharges Repeat the same procedure for sharp cornered wide crest weir Predict the type of flow at every section Compare depths with critical depth for every discharge value and report the type of flow. Draw flow profile over the hump for both types of humps.


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OBSERVATION & CALCULATION:

WEIR TYPE

Height (mm)

Width (mm)

ROUND CORNER

120

400

SHARP CORNER

60

400

DEPTH OF FLOW (mm) Sr.#

WEIR TYPE

Q m3/sec

Yc (mm)

Up Stream

FLOW CONDITOINS

over hump

Down Stream

Y1

Y2

Y3

Yavg

Y1

Y2

Y3

Yavg

Y1

Y2

Y3

Yavg

u/s

Over hump

d/s

0.006323

35.64

172

172

171

171.67

162

150

140

150.67

11

19

24

18.00

Sub Critical

Sub Critical

Super Critical

0.01058

50.24

189

190

188

189.00

177

161

142

160.00

12

22

32.5

22.17

Sub Critical

Sub Critical

Super Critical

3

0.013263

58.41

202

202

200

201.33

190

169

152

170.33

23

25

37

28.33

Sub Critical

Sub Critical

Super Critical

4

0.008488

43.37

120

121

120

120.33

115

97

92

101.33

19

23

23

21.67

Sub Critical

Sub Critical

Super Critical

0.011659

53.60

134

135

133

134.00

127

100

99

108.67

20

30

39

29.67

Sub Critical

Sub Critical

Super Critical

0.015228

64.04

148

149

148

148.33

140

108

106

118.00

30

37

44

37.00

Sub Critical

Sub Critical

Super Critical

1 2

5

ROUND CORNER WEIR

SHARP CORNER WEIR

6

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SURFACE WATER PROFILES: Round Corner Broad Crested Weir: 0.25 ) 0.2 m ( H T 0.15 P E D R E 0.1 T A W 0.05

Q = .006323 m3/s

0 0

1

2

3

4 HORIZONTAL DISTANCE (m)

5

6

7

0.25 ) 0.2 m (

Q = .01053m3/s

8


SURFACE WATER PROFILES: Round Corner Broad Crested Weir: 0.25 ) 0.2 m ( H T 0.15 P E D R E 0.1 T A W 0.05

Q = .006323 m3/s

0 0

1

2

3


5

6

7

8

0.25 ) 0.2 m ( H T 0.15 P E D R E 0.1 T A W 0.05

Q = .01053m3/s

0 0

1

2

3

21


5

6

7

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0.25 ) 0.2 m ( H T P 0.15 E D R E 0.1 T A W 0.05

Q = .0.013263m3/s

0 0

1

2

3


5

6

7

Sharp Corner Broad Crested Weir:

0.14 ) 0.12 m ( H 0.1 T P

Q = 0.008488m3/s

8


0.25 ) 0.2 m ( H T P 0.15 E D R E 0.1 T A W 0.05

Q = .0.013263m3/s

0 0

1

2

3


5

6

7

8

Sharp Corner Broad Crested Weir:

0.14 ) 0.12 m ( H 0.1 T P E D 0.08 R E T 0.06 A W 0.04

Q = 0.008488m3/s

0.02 0 0

1

2

3

4

5

6

7

8

HORIZONTAL DISTANCE (m)

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0.14 ) 0.12 m ( H 0.1 T P E 0.08 D R 0.06 E T A W 0.04 0.02

Q = 0.011659m3/s

0 0

1

2

3


5

6

7

0.18 0.16 ) m ( H T P E D R

0.14 0.12 0.1 0.08

Q = 0.015228 m 3/s

8


0.14 ) 0.12 m ( H 0.1 T P E 0.08 D R 0.06 E T A W 0.04 0.02

Q = 0.011659m3/s

0 0

1

2

3


5

6

7

8

0.18 0.16 ) m 0.14 ( H 0.12 T P E 0.1 D R 0.08 E T A 0.06 W 0.04

Q = 0.015228 m 3/s

0.02 0 0

1

2

3

23


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RESULTS: The Flow is sub Critical at upstream in both cases. The Flow is subcritical over weir in both cases. The Flow in all of the above cases is Supercritical at the downstream side immediately after the weir.

6

7

8


RESULTS: The Flow is sub Critical at upstream in both cases. The Flow is subcritical over weir in both cases. The Flow in all of the above cases is Supercritical at the downstream side immediately after the weir.

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EXPERIMENT # 04 TO STUDY THE FLOW CHARACTERISTICS OF HYDRAULIC JUMP DEVELOPED IN LAB FLUME OBJECTIVES 1. To physically achieve the hydraulic jump in lab flume. 2. To measure the physical dimensions of hydraulic jump. 3. To calculate the energy loses through hydraulic jump. 4. To plot water surface profiles of the hydraulic jump for various discharges.

APPARATUS S-6 tilting lab flume with Manometer Flow arrangement


EXPERIMENT # 04 TO STUDY THE FLOW CHARACTERISTICS OF HYDRAULIC JUMP DEVELOPED IN LAB FLUME OBJECTIVES 1. To physically achieve the hydraulic jump in lab flume. 2. To measure the physical dimensions of hydraulic jump. 3. To calculate the energy loses through hydraulic jump. 4. To plot water surface profiles of the hydraulic jump for various discharges.

APPARATUS S-6 tilting lab flume with Manometer Flow arrangement Slope adjusting scale Hook gauge

RELATED THEORY HYDRAULIC JUMP The rise of water level which takes place due to transformation of super critical flow to sub critical flow

is termed as hydraulic jump.

PRACTICAL APPLICATIONS OF HYDRAULIC JUMP

To dissipate the energy of water flowing over the hydraulic structures and thus preventing scouring (vertical erosion) downstream of structures. To recover head or raise the water level on the downstream of a hydraulic structure and t hus to maintain high water level in the channel for irrigation or other water distribution purposes. To increase the weight of apron and thus reduce uplift pressure under the structure by raising water depth on the apron. Apron: Layer of flexible material provided on the downstream floor. It act as an inverted filter.

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HYDRAULICS ENGINEERING LAB MANUAL To mix chemicals used for water filtration etc. EXPRESSION FOR DEPTH OF HYDRAULIC JUMP

From the figure below. Depth of hydraulic jump

=

We can find d 2 , for known value of d 1 , by using expression,

EXPRESSION FOR LOSS OF ENERGY DUE TO HYDRAULIC JUMP

On simplifying, we can find head loss for known values of d 1 and d2 ,

LENGTH OF HYDRAULIC JUMP

The length between two sections where one section is taken just before the hydraulic jump and second section is taken just after the hydraulic jump is termed as length of hydraulic jump. Approximate length of hydraulic jump =

26

5 -7 times depth of hydraulic jump

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HYDRAULICS ENGINEERING LAB MANUAL LOCATIONOF HYDRAULIC JUMP

Location of hydraulic jump is governed by two factors, I)

d2

II) Y2

CASE – 01

(Depth of flow just after the hydraulic jump) (Normal depth of flow on downstream side of hydraulic structure)

When d2 < Y2 Crest

U/S

D/S

y2

In Case – 01, Hydraulic jump will be formed over the glaces of hydraulic structure as shown in the figure and it will be weak jump/Submerged jump.

CASE – 02

When d2 = Y2

Crest

U/S

d2

D/S

y2

In Case – 02, Hydraulic jump will be formed on the toe of hydraulic structure as shown in the figure and it will be a relatively strong jump than Case - 01.

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HYDRAULICS ENGINEERING LAB MANUAL CASE – 03

When d2 > Y2

U/S d2

D/S

y2

In Case – 03, Hydraulic jump will be formed ahead of hydraulic structure as shown in the fig. And it will be a relatively strong jump as compared to Case – 01 and Case – 02. Comparatively, Case – 02 is ideal case with sufficient energy dissipation and structure will also be safe (because jump will be formed at the toe of structure). CLASSIFICATION OF HYDRAULIC JUMP Type of hydraulic jump is defined based on Froude’s number,

i)

FN =

1.0

No jump

ii)

FN =

1.0 – 1.7

Undulated jump/Roller type jump

iii)

FN

=

1.7 – 2.5

Weak jump

iv)

FN =

2.5 – 4.5

Oscillating jump

v)

FN

4.5 – 9.0

Steady jump

vi)

FN >

9.0

Strong jump

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=

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HYDRAULICS ENGINEERING LAB MANUAL PROCEDURE Adjust the S-6 Tilting flume at a slope and check if there is any problem in arrangement or anything residual inside the flume causing obstruction in flow. Setup a specific discharge in the flume. Note down the depth of the water surface before, after and at the hydraulic jump. Repeat the above procedure with by increasing discharge. Complete the table of observations and calculations and plot the water surface profile for all discharges.

PRECAUTIONS The height should not be measured near the joints or at points where there is turbulence in flume. The height measuring needle must be adjusted precisely. The tip of the needle must be just touching the water surface while taking observations. The reading measurement at the hydraulic jump is difficult, so note the flow carefully and take the reading at desired point.

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OBSERVATION & CALCULATION: Width of Flume -0.3 m

SR. #

Discharge Q (m3 /sec)

Depth of Flow (m)

Horizontal Distances (m)

(yo)

(y1)

(y2)

(xo)

(x1)

(x2)

yc (m)

Height of Jump Hj (y2-y1) (m)

Length of Jump (x2-x1) (m)

Loss of Energy at jump

hL (m)

V1 = Q/(B.y1) (m/sec)

FN1

1

0.000798

0.0227

0.02

0.076

2

3.982

4.13

0.009

0.056

0.145

0.028884

0.133

0.3

2

0.010925

0.0275

0.0236

0.0847

2

4.112

4.36

0.051

0.0611

0.252

0.028528

1.543079096

3.21

0.012326

0.03

0.026

0.0936

2

4.206

0.056

0.0676

0.252

0.031734

1.58025641

3.13

4

0.013853

0.0327

0.0298

0.0938

2

4.302

4.58

0.06

0.064

0.282

0.023446

1.549552573

2.87

5

0.015228

0.0361

0.0323

0.0995

2

4.386

4.68

0.064

0.0672

0.291

0.023606

1.571517028

2.79

6

0.016488

0.0391

0.035

0.107

2

4.63

4.79

0.068

0.072

0.159

0.024916

1.570285714

2.68

3

4.46

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Type of Jump

Roller type jump Oscillating Jump Oscillating Jump Oscillating Jump Oscillating Jump Oscillating Jump

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HYDRAULIC JUMP PROFILES: st 1 Observation:

1st Observation 0.12 ) 0.1 m ( ) y0.08 ( w o l F f 0.06 o h t 0.04 p e D 0.02

0 1.5 nd

2

2.5

Horizontal Distance (x) (m)

Observation:

2nd Observation 0.12 0.1

3.5

4.5

Theoretical Sequent Depth (y2) m

0.0084 0.0491 0.0533 0.0580 0.0619 0.0654


HYDRAULIC JUMP PROFILES: st 1 Observation:

1st Observation 0.12 ) 0.1 m ( ) y0.08 ( w o l F f 0.06 o h t 0.04 p e D 0.02

0 1.5 nd

2

2.5


3.5

4.5

Observation:

2nd Observation 0.12 ) 0.1 m ( ) y0.08 ( w o l F0.06 f o h t 0.04 p e D 0.02

YC

0 1.5

2.5

3.5 Horizontal Distance (x) (m)

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4.5

5.5

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rd

3 Observation:

3rd Observation 0.12 ) 0.1 m ( ) y ( 0.08 w o l F f0.06 o h t 0.04 p e D 0.02

YC

0 1.5

2.5

Horizontal Distance (x) (m) 3.5

th

4 Observation:

4th Observation 0.12 0.1

4.5

5.5


rd

3 Observation:

3rd Observation 0.12 ) 0.1 m ( ) y ( 0.08 w o l F f0.06 o h t 0.04 p e D 0.02

YC

0 1.5

2.5

Horizontal Distance (x) (m) 3.5

4.5

5.5

th

4 Observation:

4th Observation 0.12 0.1 ) m ( ) y 0.08 ( w o l F f 0.06 o h t p 0.04 e D 0.02 0 1.5

2.5

3.5


32

4.5

5.5

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th

5 Observation:

5th Observation 0.12 ) 0.1 m ( ) y0.08 ( w o l F f 0.06 o h t0.04 p e D 0.02

YC

0 1.5

2.5


th

6 Observation:

6th Observation 0.12

4.5

5.5


th

5 Observation:


YC

0 1.5

2.5


4.5

5.5

4.5

5.5

th

6 Observation:


YC

0 1.5

2.5


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HYDRAULICS ENGINEERING LAB MANUAL COMMENTS: According to definition hydraulic jump is formed due to change in slope or change of flow from super critical to sub critical flow, but in observation 1 there is no change of slope or there is no change in flow, this might be due to some error while performing experiment. The reading measurement at the hydraulic jump was difficult as the turbulence was not allowing us to consider a constant point for observation. There might be error in depth of flow values due to momentary variation in height of the jump. Some Water is also flowing under the hump and this may disturb the results adversely.

Lab Manual (Hydraulics Engineering)

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