flow in open channel

FACULTY OF CIVIL AND ENVIRONMENTAL

ENGINEERING

DEPARTMENT OF WATER & ENVIROMENTAL ENGINEERING

WATER ENGINEERING LABORATORY

LAB REPORT Subject Code BFC 21201

Code & Experiment Title MKA – 02 ; FLOW IN OPEN CHANNEL

Course Code 2 BFF/1

Date 14 NOVEMBER 2011

Section / Group 2/5

Name AFANDI BIN ABD WAHID (DF100122)

Members of Group 1.MUHAMMAD IKHWAN BIN ZAINUDDIN (DF100018)

2.MOHD HASIF BIN AZMAN (DF100079)

3.MUHAMMAD HUZAIR BIN ZULKIFLI (DF100040)

Lecturer/Instructor/Tutor CIK AMNANI BIN ABU BAKAR

EN JAMILULLAIL BIN AHMAD TAIB

Received Date 21 NOVEMBER 2011

Comment by examiner

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 : AFANDI BIN ABD WAHID

MATRIC NO. : DF100122

DATE : 21 NOVEMBER 2011


(SEC)


ENGINEERING


ENGINEERING


BATU PAHAT, JOHOR




……………………………………….

(STUDENT SIGNATURE)

NAME : MUHAMMAD IKHWAN BIN ZAINUDDIN




(SEC)


ENGINEERING


ENGINEERING


BATU PAHAT, JOHOR




……………………………………….

(STUDENT SIGNATURE)

NAME : MOHD HASIF BIN AZMAN




(SEC)


ENGINEERING


ENGINEERING


BATU PAHAT, JOHOR




……………………………………….

(STUDENT SIGNATURE)

NAME : MUHAMMAD HUZAIR BIN ZULKIFLI



PART A : THE HYDRAULIC JUMPS

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-than-

critical 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 and to observe the flow patterns obtained.

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

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 :

g2

vd

g2

vdH

2

bb

2

aa

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, .dd4/ddH 31

3

13

5.0 EQUIPMENT

Figure 1: Self-contained Glass Sided

Tilting Flume.

Figure 2: Adjustable Undershot Weir

Figure 3: Control Panel

Figure 5: Hook and Point Gauge

Figure 4: Instrument Carrier

Figure 6: Slope Adjustment

6.0 PROCEDURES

1. Ensure the flume is level, with the downstream tilting overshot weir, E at the bottom

of its travel. Measure and record the actual breadth b (m) of the undershot weir. Install

the undershot weir towards the inlet end of the flume and ensure that it is securely

clamped in position.

2. Adjust the undershot weir to position the sharp edge of the weir 20mm above the bed

of the channel. Increase the height of the tilting overshot weir until the downstream

level just stars to rise.

3. Gradually open the flow control valve and adjust the flow until an undular jump is

created with small ripple decaying towards the discharge end of the working section.

Observe and sketch the flow pattern.

4. Increase the height of water upstream of the undershot weir by increasing the flow

rate and increase the height of the titling overshot weir to create a hydraulic jump in

the centre of the working section. Observe and sketch the flow pattern.

5. Measure and record the values of d1, d3, dg, and q. repeat this for other flow rates q

(upstream head) and heights of the gate dg

7.0 RESULT

Weir breadth, b = 0.300 m

Weir

opening,

dg

(m)

Upstream

flow

depth, do

(m)

Flow Depth

above jump,

d1

(m)

Flow depth

below jump,

d3

(m)

Flow rate

(m3/s)

ΔH V1 ΔH

d1

d3

d1

0.020 0.416 0.013 0.124 0.012 0.2121 2.000 16.32 9.54

0.030 0.228 0.017 0.101 0.012 0.0863 1.333 5.08 5.94

0.040 0.146 0.024 0.094 0.012 0.0380 1.000 1.58 3.92

1. Calculate V1 and plot dg against V1

2. Calculate ΔH / d1 and plot ΔH / d1 against d3 / d1

3. Calculate dc and verify d1 < dc < d3

8.0 DATA ANALYSIS

Calculation for : ∆H = (d3 – d1)

3

4d1d3

= (0.124 - 0.013) 3

4 (0.013)(0.124)

= 0.2121 m

= (0.101 - 0.017) 3

4 (0.017)(0.101)

= 0.0863 m

= (0.094 - 0.024) 3

4 (0.024)(0.094)

= 0.0380 m

Calculation for : V1 , Q = AV

V = Q

A

A = dg x b

= 0.020 x 0.300

= 0.006 m2

Therefore,

V = 0.012

0.006

= 2.000 m/s

A = dg x b

= 0.030 x 300

= 0.009 m2

Therefore,

V = 0.012

0.009

= 1.333 m/s

A = dg x b

= 0.040 x 300

= 0.012 m2

Therefore,

V = 0.012

0.012

= 1.000 m/s

Calculation for : ∆H

d1

= 0.2121

0.013

= 16.32

= 0.0863

0.017

= 5.08

= 0.0380

0.024

= 1.58

Calculation for : d3

d1

= 0.124

0.013

= 9.54

= 0.101

0.017

= 5.94

= 0.094

0.024

= 3.92

Calculate for: dc = q2

g

q = Q

b

= 0.012

0.300

= 0.040 m3/s

m

Therefore,

dc = 0.0402

9.81

= 0.055 m

Therefore weir opening:

dg d1 < dc < d3

20

30

40

0.013 < 0.055 < 0.124

0.017 < 0.055 < 0.101

0.024 < 0.055 < 0.094

9.0 QUESTION

1. Verify the force of the stream on either side of the jump is the same and that the

specific energy curve predicts a loss equal to ΔH / dc.

Fbefore = Fafter

2. Suggest application where the loss of energy in hydraulic jump would be

desirable. How is the energy dissipated?

The hydraulic jump flow process can be illustrated by use of the specific energy

concept. Equation loss energy can be written in term of the specific energy:

E = do + V2/ 2g

⅓

⅓

Where do and E are feet. Because of the head loss across the jump, the upstream

values of E are different. About the graph, (1) to state (2) the fluid does not

proceed along the specific energy curve and pass through the critical condition.

The energy dissipates when water flow at weir opening and the energy became 0

because d0 and d3 has are force from adverse. Same like the equation,

Fbefore = Fafter.

10.0 DISCUSSION

Practical applications of hydraulic jump are:

1. To dissipate energy in water flowing over hydraulic structures as dams, weirs, and

others and prevent scouring downstream structures.

2. To raise water level on the downstream side for irrigation or other water distribution

purposes.

3. To increase weight on an apron and reduce uplift pressure under a structure by raising

the water depth on the apron.

4. To indicate special flow conditions such as the existence of supercritical flow or the

presence of a control section so that a gaging station maybe located.

5. To mix chemicals used for water purification.

6. To aerate water for city water supplies.

7. To remove air pockets from water supply lines and prevent air locking.

11.0 CONCLUSION

The conclusion from the experiment, we can investigate the characteristic a

standing wave (the hydraulic jump) produced when waters beneath an undershot weir and

to observe the flow patterns obtained. From the experiment, we can get the force at weir

opening, ∆H. In the water channel, 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 are greater than critical and must be

accompanied by loss of energy.

From the result, we get the inverse line from graph gd1 against v1 and curve line

from graph Δ H/d1 against d3/d1. Both graphs are sloping downward. Final result we can

get the value of dc between d1 and d3. So the objective achieved and the experiments are

success. Reason the experiment perform because almost drain are open channel. From the

experiment, we know about water flowing.

12.0 REFERENCES

i. John J.E.A. 1988. Introduction to Fluid Mechanics, pp 330-342. Prentice Hall, Inc.

ii. Chaudhry, M. H. 1993. Open Channel Flow, pp 302-408. Prentice-Hall, Inc.

iii. Simon, A. L.1997. Hydraulics, pp 283-312. Prentice Hall, Inc

iv. http://www.engineeringcivil.com (serve on 19/11/2011)

http://www.engineeringcivil.com/

PART B: THE FORCE ON A SLUICE GATE

1.0 INTRODUCTION

The Sluice gate is a device used to control the passage of water in an open

channel. When properly calibrated it may also serve as a means of flow measurement.

As the lower edge of the gate opening is flush with the floor of the channel, contraction

of the bottom surface of the issuing stream is entirely suppressed. Side contraction will

of course depend on the extent to which the opening spans the width of the channel.

A variety of gate-type structure is available for flow rate control at the crest of

an overflow spillway, or at the entrance of an irrigation canal or river from a lake.

Three typical types are vertical gate, radial gate and drum gate. The flow under a gate is

said to be free outflow when the fluid issues as a jet of supercritical flow with a free

surface open to the atmosphere.

In certain situation, the depth downstream of the gate is controlled by some

downstream obstacle and the jet of water issuing from under the gate is overlaid by a

mass of water that is quite turbulent.

Picture 1: Drowned outflow from a sluice gate.

2.0 OBJECTIVE

To determine the relationship between upstream head and trust on a sluice gate

(undershot weir) for water flowing under the sluice gate.

3.0 LEARNING OUTCOMES

At the end of the course, students should be able to apply the knowledge and skill

they have learned to:

a) Understand the basic terms and concept of a sluice gate.

b) Understand on the characteristics of the force on a sluice gate.

4.0 THEORY

It can be shown that the resultant force on the gate is given by the equation :

The gate thrust for hydrostatic pressure distribution is given by the equation :

where Fg is the resultant gate thrust (N), FH is the resultant hydrostatic thrust (N), q is

volume flowrate (m/s), ρ is density of fluid (kg/m3), g is the gravitational constant

(9.81m/s2), b is breadth of gate (m), dg is height of upstream opening (m), d0 is upstream

depth of flow (m) and d1 is downstream depth of flow (m).

5.0 EQUIPMENT

0

1

1

2

1

2

02

1 112

1

d

d

bd

g

d

dgdFg

20

2

1gH ddgF

Figure 1: Self-contained Glass

Sided Tilting Flume.

Figure 2: Adjustable Undershot

Weir

Figure 3: Control Panel

Figure 4: Hook and Point Gauge

Figure 6: Instrument Carrier

Figure 6: Slope Adjustment

6.0 PROCEDURES

1. Ensure the flume is level, with the downstream tilting overshot weir at the bottom of its

travel its travel. The actual breadth b (m) of the undershot weir are measured and

recorded.

2. The undershot weir adjusted to set its bottom edge 20mm above the bed of the channel.

3. Introduce water into the flume until do = 200mm. with do at this position, the readings

for q and d1 are taken. Raise the undershot weir in increments of 10mm, maintaining

constant do by varying q. At each level of the weir, record the values of dg, d1 and q.

4. The procedure with a constant flow q, allowing do to vary are repeated and the value of

do and d1 are recorded.

7.0 RESULT

Weir breadth, b = 300 m

Weir

opening,

dg

(m)

Upstream

flow

depth, do

(m)

Downstream

Flow Depth,

d1

(m)

Flow

Rate

q (m3/s)

Gate Thrust

Fg (N)

Hydrostatic

Thrust, FH

(N)

Fg

FH

dg

do

0.025 0.292 0.016 0.012 -1.931 x106 349.67 -5.52 0.086

0.030 0.225 0.018 0.012 -1.58 x 106 186.51 -8.47 0.133

0.035 0.167 0.022 0.012 -1.48 x 106 85.46 -17.32 0.210

0.040 0.138 0.024 0.012 -1.12 x 106 47.11 -23.77 0.290

8.0 DATA ANALYSIS

Calculation for Gate Thrust at Weir Opening = 0.025 m

Gate Thrust =


Gate Thrust =


Gate Thrust =


Gate Thrust =

0

1

1

2

1

2

02

1 112

1

d

d

bd

g

d

dgdFg

292.0

016.01

)016.0)(300.0(

)81.9(10001

016.0

292.0)016,0)(81.9)(1000(

2

1 22

gF

Fg = -1.931 x 106 N

0

1

1

2

1

2

02

1 112

1

d

d

bd

g

d

dgdFg

225.0

018.01

)018.0)(300.0(

)81.9(10001

018.0

225.0)016,0)(81.9)(1000(

2

1 22

gF

Fg = -1.58 x 106 N

0

1

1

2

1

2

02

1 112

1

d

d

bd

g

d

dgdFg

167.0

022.01

)022.0)(300.0(

)81.9(10001

022.0

167.0)016,0)(81.9)(1000(

2

1 22

gF

Fg = -1.48 x 106 N

0

1

1

2

1

2

02

1 112

1

d

d

bd

g

d

dgdFg

138.0

024.01

)024.0)(300.0(

)81.9(10001

024.0

138.0)016,0)(81.9)(1000(

2

1 22

gF

Fg = -1.12 x 106 N

Calculation for Hydrostatic Thrust at Weir Opening = 0.025 m

Hydrostatic Thrust,


Hydrostatic Thrust,


Hydrostatic Thrust,


Hydrostatic Thrust,

20

2

1gH ddgF

2025.0292.0)81.9)(1000(2

1HF

FH = 349.67 N

20

2

1gH ddgF

FH = 186.51 N

20

2

1gH ddgF

2035.0167.02

1 gFH

FH = 85.46 N

20

2

1gH ddgF

2040.0138.0)81.9)(1000(2

1HF

FH = 47.11 N

2030.0225.0)81.9)(1000(2

1HF

Calculation for Fg/FH ratio at Weir Opening = 0.025 m

Fg = - 1.931 x 106

FH 349.67

= - 5.52


Fg = - 1.580 x 106

FH 186.51

= - 8.47


Fg = - 1.48 x 106

FH 85.46

= - 17.32


Fg = - 1.12 x 106

FH 47.11

= - 23.77

Calculation for dg/do ratio at Weir Opening = 0.025 m

dg = 0.025

do 0.292

= 0.086


dg = 0.030

do 0.225

= 0.133


dg = 0.035

do 0.167

= 0.210


dg = 0.040

do 0.138

= 0.290

9.0 QUESTIONS

1. Plot graph of the ratio Fg / FH against the ratio dg / do. (Refer graph)

2. Comment of the graph obtained.

Based on the graph, the pattern of the graph is linear line and an increased. When the

value of dg /do are increased , the value of Fg / FH also increased.

3. Compared your calculated values for Fg and FH and comment on any differences.

After we are calculated Fg with used this formula,

Fg = ½ ρgd12 [ (d0

2 / d1

2 ) - 1 ] – ρg / bd1 [ 1 – (d1 / d0 )], we get the value are in negative

(-ve) and when we calculated FH with FH = ½ ρg ( d0 - dg )2 , we get the value in positive

(+ve). Fg is resultant gate thrust (N) and FH is resultant hydrostatic thrust (N). We can

conclude that before the water is flow to the sluice gate, the force are FH are in positive

(+ve) because is follow the direction of the water flow. The force are happened after

sluice gate are Fg in negative (-ve) because the resultant force of the flow is opposite the

direction.

4. What is the effect of flow rate on the result obtained?

From the result, the more flow rate will give the less thrust for both of the gate and the

hydrostatic. This is because of the decreasing pressure at both of them.

10.0 DISSCUSSION

Floodgates are adjustable gates used to control water flow in reservoir, river, stream, or

levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in

sluices and canals, or they may be designed to stop water flow entirely as part of a levee or storm

surge system.

Since most of these devices operate by controlling the water surface elevation being

stored or routed, they are also known as crest gates. In the case of flood bypass systems,

floodgates sometimes are also used to lower the water levels in a main river or canal channels by

allowing more water to flow into a flood bypass or detention basin when the main river or canal

is approaching a flood stage. Picture below shown the floodgates.

Tokyo floodgates created to protect from typhoon surges

Another example of floodgate or sluice gate that we can explore is as shown below :

A sluice gate on the Harran canal

http://en.wikipedia.org/wiki/Lake

http://en.wikipedia.org/wiki/River

http://en.wikipedia.org/wiki/Stream

http://en.wikipedia.org/wiki/Levee

http://en.wikipedia.org/wiki/Spillway

http://en.wikipedia.org/wiki/Dam

http://en.wikipedia.org/wiki/Sluice

http://en.wikipedia.org/wiki/Canals

http://en.wikipedia.org/wiki/Storm_surge

http://en.wikipedia.org/wiki/Storm_surge

http://en.wikipedia.org/wiki/Detention_basin

http://en.wikipedia.org/wiki/Tokyo

http://en.wikipedia.org/wiki/Typhoon

http://en.wikipedia.org/wiki/Southeastern_Anatolia_Project

Tainter gate diagram Tainter gates and spillway

Drum gates are controlled with valves Drum gates on a diversion dam

.

http://en.wikipedia.org/wiki/Tainter_gate

http://en.wikipedia.org/wiki/Diversion_dam

11.0 CONCLUSION

The flow through a channel in which a gate partially obstructs the flow will be used for

this measurement of total force. This obstruction is called a sluice gate (see Figure 1). The flow is

from left to right and enters at a velocity Vo. The fluid in the upstream section builds up against

the gate to a level y0, and exits the upstream section under the gate of height b. The fluid attains a

higher velocity V1 as it passes under the gate and a shallower free surface height y1 downstream.

Three assumptions will be made in this derivation of the equation for horizontal force on

a sluice gate:

1) The viscous force at the bottom of the channel and the energy dissipation at the

gate are negligible.

2) The flow is steady and has a uniform velocity distribution at the inlet and outlet

sections.

3) Flow at upstream and downstream sections is uniform and the effect of the side-

walls is negligible.

Figure 1. Flow under a vertical sluice gate.

12.0 REFERENCES

1. John J.E.A. 1988. Introduction to Fluid Mechanics, pp 330-342. Prentice Hall, Inc.

2. Chaudhry, M. H. 1993. Open Channel Flow, pp 302-408. Prentice-Hall, Inc.

3. Chow, V. T. 1959. Open Channel Hydraulics, pp 608-710. McGraw-Hill, Inc.

flow in open channel

Documents

water surface

hydraulic drop

mohd hasif bin azman

afandi bin abd wahid

df100040 date

df100018 date

df100079 date

df100122 date