HYDRAULICS JUMP

FACULTY OF CIVIL AND ENVIRONMENTAL ENGINEERING DEPARTMENT OF WATER & ENVIROMENTAL ENGINEERING WATER ENGINEERING LABORATORY

LAB REPORT Subject Code Code & Experiment Title Course Code Date Section / Group Name Members of Group Lecturer/Instructor/Tutor Received Date

Comment by examiner

BFC 21201 OPEN ENDED LAB – THE HYDRAULICS JUMP 2 BFF/1 12 DECEMBER 2011 2/4 MUHAMMAD IKHWAN BIN ZAINUDDIN (DF100018) AHMAD FARHAN BIN RAKAWI (DF100142) IDAMAZLIZA BINTI ISA (DF100128) CIK AMNANI BIN ABU BAKAR EN JAMILULLAIL BIN AHMAD TAIB 19 DECEMBER 2011

Received

STUDENTS’ ETHICAL CODE (SEC) DEPARTMENT OF WATER & ENVIRONMENTAL ENGINEERING FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING UNIVERSITI TUN HUSSEIN ONN MALAYSIA BATU PAHAT, JOHOR

“I declare that I have prepared this report with my own efforts. I also declare not receive or give any assistance in preparing this report and make this affirmation in the belief that nothing is in, it is true”

………………………………………. (STUDENT SIGNATURE) NAME : MUHAMMAD IKHWAN BIN ZAINUDDIN MATRIC NO. : DF100018 DATE : 19 DECEMBER 2011

1.0

INTRODUCTION The concept of the hydraulic jump when the hydraulic drop that occurs at a sudden drop in the bottom of a channel, and the free surface flow around obstructions like bridge piers. A hydraulic jump forms when a supercritical flow changes into a subcritical flow. The change in the flow regime occurs with a sudden rise in water surface. Considerable turbulence, energy loss and air entrainment are produced in the hydraulic jump. A hydraulic is used for mixing chemicals in water supply systems, for dissipating energy below artificial channel controls, and as an aeration device to increase the dissolved oxygen in water. In a hydraulic jump there occurs a sudden change in liquid depth from less-thancritical to greater-than-critical depth. The velocity of the flow changes from supercritical to subcritical as a result of the jump. This transition takes place over a relatively short distance, usually less than 5 times the depth of flow after the jump, over which the height of the liquid increase rapidly, incurring a considerable loss of energy. An example of a hydraulic jump can be observed when a jet of water from a faucet strikes the horizontal surface of the kitchen sink. The water flows rapidly outward and a circular jump occurs. We shall restrict the derivation of the basic equation of the hydraulic jump to rectangular horizontal channels. First, we shall determine the downstream depth of the jump by using the momentum and continuity equations for one-dimensional flow. Then the energy loss due to the jump will be evaluated, using the energy equation.

2.0

OBJECTIVE To investigate the characteristic a standing wave (the hydraulic jump) produced when waters beneath an undershot weir have a slope and will be compare with previous data which it does not have a slope.

3.0

LEARNING OUTCOMES At the end of the course, students should be able to apply the knowledge and skills they have learned to: a) Understand the concept and characteristics of hydraulic jump. b) Understand the factors which influence the hydraulic jump.

4.0

THEORY

Figure 1– Hydraulic Jump without Slope

Figure 2 – Hydraulic Jump with Slope

When water flowing rapidly changes to slower tranquil flow, a hydraulic jump or standing wave is produced. This phenomenon can be seen where water shooting under a sluice gate mixes with deeper water downstream. It occurs when a depth less than critical changes to a depth which is greater than critical and must be accompanied by loss of energy. An undular jump occurs when the change in depth is small. The surface of the water undulates in a series of oscillations, which gradually decay to a region of smooth tranquil flow. A direct jump occurs when the change in depth is great. The large amount of energy loss produces a zone of extremely turbulent water before it settles to smooth tranquil flow.

By considering the forces acting with the fluid on either side of a hydraulic jump of unit width it can be shown that : H  d a 

2 2 va  v    d b  b  2g  2g 

Where ΔH is the total head loss across jump (energy dissipated) (m). va is the mean velocity before jump (m/s), d a is the depth of flow before hydraulic jump (m). vb is the mean velocity after hydraulic jump (m) and d b is the depth of flow after hhydraulic jump (m). Because the working section is short, d

a

≈ db and db ≈ d3. Therefore,

simplifying the above equation, H  d 3  d1  / 4d1d 3 . 3

5.0

EQUIPMENT

Figure 3: Self-contained Glass Sided Tilting Flume.

Figure 5: Control Panel

Figure 4: Adjustable Undershot Weir

Figure 6: Instrument Carrier

Figure 7: Hook and Point Gauge

6.0

Figure 8: Slope Adjustment

PROCEDURES i.

Set up the opening gate with 40mm and make sure there is no leakage between the gate and open channel wall.

ii.

Adjust the slope, So with +400 before switch on the pump.

iii.

Switch on the pump switch and control the gate valve to get the flow depth.

iv.

Wait and observe the movement of water until the water level remain and take the reading of flow depth, do (a depth before the gate).

v.

Rotate the rail gates slowly and make sure it can form a waterfall

vi.

Water jump must be formed close to the gate. Wait a while until the jump is fixed.

vii.

Take the reading of flow depth, d1 (in front of the gate, before the water jump), d3 (in front of the gate, after the water jump) and flow rate, q (m3/s) at the control panel.

viii.

Before take the reading of flow depths, make sure the gauge must be at zero (0).

ix.

After take the reading, raise the door gate to 40mm and slope, So -400.

x.

Make sure the water jump formed before still at the same place. If the jump move, set the rail gate slowly using gate holder and make sure the jump is at the place.

xi.

After the water jump fixed and stop (no movement), repeat procedure 6

xii.

Switch off the pump switch after ended the experiment.

7.0

RESULT

Weir breadth, b = 0.300 m

+ 400

Weir opening, dg (m) 0.0400

Upstream flow depth, do (m) 0.1120

Flow Depth above jump, d1 (m) 0.0250

Flow depth below jump, d3 (m) 0.0870

- 400

0.0400

0.1550

0.0260

0

0.0400

0.1460

0.0240

Slope, So

1. Calculate V1 and plot d1 against V1 2. Calculate ΔH / d1 and plot ΔH / d1 against d3 / d1 3. Calculate dc and verify d1 < dc < d3

Flow rate (m3/s)

ΔH

V1

ΔH d1

d3 d1

0.0110

0.0274

0.9167

1.0960

3.4800

0.0900

0.0130

0.0280

1.0833

1.0769

3.4615

0.0940

0.0120

0.0380

1.0000

1.5833

3.9167

8.0

DATA ANALYSIS Calculation from left to right: slope at +400, slope at -400 and slope at 0 (d3 – d1)3 4d1d3 = (0.090 - 0.026) 3 4 (0.026)(0.090) = 0.0280 m

= (0.094 - 0.024) 3 4 (0.024)(0.094) = 0.0380 m

A = dg x b = 0.040 x 0.300 = 0.012 m2

Q = AV V= Q A A = dg x b = 0.040 x 0.300 = 0.012 m2

A = dg x b = 0.040 x 0.300 = 0.012 m2

Therefore, V = 0.011 0.012 = 0.9167 m/s

Therefore, V = 0.013 0.012 = 1.0833 m/s

Calculation for :

∆H

= (0.087 - 0.025) 3 4 (0.025)(0.087) = 0.0274 m Calculation for :

Calculation for :

V1 ,

=

Therefore, V = 0.012 0.012 = 1.000 m/s

∆H d1

= 0.0274 0.025 = 1.0960

= 0.0280 0.026 = 1.0769

= 0.0380 0.024 = 1.5833

= 0.090 0.026 = 3.4615

= 0.094 0.024 = 3.9167

q=Q b = 0.011 0.300 = 0.0367 m3/s m

⅓ q2 g q=Q b = 0.013 0.300 = 0.0433 m3/s m

q=Q b = 0.012 0.300 = 0.0400 m3/s m

Therefore, ⅓ dc = 0.03672 9.81 = 0.0516 m

Therefore, ⅓ dc = 0.04332 9.81 = 0.0576 m

Therefore, ⅓ dc = 0.04002 9.81 = 0.0546 m

Calculation for :

d3 d1

= 0.087 0.025 = 3.4800 Calculate for:

dc =

Therefore:

9.0

So

d1 < dc < d3

+ 400

0.0250 < 0.0516 < 0.0870

- 400

0.0260 < 0.0576 < 0.0900

0

0.0240 < 0.0546 < 0.0940

DISCUSSION A hydraulic jump can be viewed as discontinuous waves of all frequencies (wavelengths), which are generated and propagate from a point near the jump. The waves propagate both upstream and downstream. Since a large fraction of the waves fall in a wavelength range where they are shallow water gravity waves that move at the same speed for a given depth, they move upstream at the same rate. However as the water shallows upstream, their speed drops quickly, limiting the rate at which they can propagate upstream. Shorter wavelengths, which propagate more slowly than the speed of the wave in the deeper downstream water, are swept away downstream. A fairly wide range of wavelengths and frequencies are still present, so Fourier analysis would suggest that a relatively abrupt wave front can be formed and this is indeed observed in practice. One of the most important engineering applications of the hydraulic jump is to dissipate energy in channels, dam spillways, and similar structures so that the excess kinetic energy does not damage these structures. The energy dissipation or head loss across a hydraulic jump is a function of the magnitude of the jump. The larger the jump as expressed in the fraction of final height to initial height, the greater the head loss.

10.0 CONCLUSION Based on experiment data and, I found that the velocity for both slope is entirely different. The velocity at slope +400 is 0.9167 m/s and the velocity at slope -400 is 1.0833. This situation is very different when the value of the slope is zero. The velocity value for the slope at 0 is 1.0000 m/s. Hydraulic jump for slope at -400 is lower than hydraulic jump for the slope at +400 and slope at 0. This is probably the factor of positive and negative values of the slope and flowrate. At the negative slope we had to change the flowrate from the 0.0110 m3/s (at +400) to 0.0130 m3/s for slope at -400 because of a waves occurs only at the opening gate. From the data for d1, dc and d3 in each slope is normal. We can see that d1 < dc < d3 in each slope. From the graph flow depth above jump, d1 versus velocity, v1 has shown that, slope at -400 is higher that slope at 0 and slope at +400. This condition maybe occurs because of the slope. The velocity will increased depend on the slope surface. From the graph ΔH / d1 against d3 / d1 also when slope is set to 0, the line is higher than slope at +400 and -400. In fact, I can summarize that the different slope and flowrate might be the big factor that can effect on my data. Therefore, if all three flowrate used for each slope is same, we might see be a huge difference for the data especially the velocity and heights of the water hydraulic jump.

11.0 REFERENCES i. Chaudhry, M. H. 1993. Open Channel Flow, pp 302-408. Prentice-Hall, Inc. ii. Simon, A. L.1997. Hydraulics, pp 283-312. Prentice Hall, Inc