Methodology..................................................................................................... ......................................................................................................................................... .................................... 21 Recorded values and calculations based on crump weir ...................................................................... 22 Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using over shot weir. .............................................................. ......................................................................................................................... ........................................................... 23 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 24 5th Test......................................... Test............................................................................................................... .......................................................................................................... .................................... 25 VENTURI FLUME .................................................................................... .................................................................................................................................... ................................................ 25 Apparatus used ..................................................................................................................................... ..................................................................................................................................... 25 Methodology..................................................................................................... ......................................................................................................................................... .................................... 27 Readings and calculations based on venturi flume .............................................................................. 27 Graph showing water depth (H) against Water flow rate (Q) drawn from the values obtained using Venturi flume. ................................................................................................................................... ................................................................................................................................... 29 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 31 6th Test......................................... Test............................................................................................................... .......................................................................................................... .................................... 32 HYDRAULIC JUMP AND SLUICE GATE............................................................... .................................................................................................... ..................................... 32 Methodology..................................................................................................... ......................................................................................................................................... .................................... 32 Readings and calculations based on hydraulic jumps ......................................................... ....................................................................... .............. 33 33 Graphs ............................................................... ........................................................................................................................................ .................................................................................... ........... 36 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 37 Recommendation.................................................................................................................................. .................................................................................................................................. 37 Appendix .............................................................. .................................................................................................................................... ................................................................................. ........... 40 References ........................................................... .............................................................................................................................. ................................................................................. .............. 39
Methodology..................................................................................................... ......................................................................................................................................... .................................... 21 Recorded values and calculations based on crump weir ...................................................................... 22 Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using over shot weir. .............................................................. ......................................................................................................................... ........................................................... 23 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 24 5th Test......................................... Test............................................................................................................... .......................................................................................................... .................................... 25 VENTURI FLUME .................................................................................... .................................................................................................................................... ................................................ 25 Apparatus used ..................................................................................................................................... ..................................................................................................................................... 25 Methodology..................................................................................................... ......................................................................................................................................... .................................... 27 Readings and calculations based on venturi flume .............................................................................. 27 Graph showing water depth (H) against Water flow rate (Q) drawn from the values obtained using Venturi flume. ................................................................................................................................... ................................................................................................................................... 29 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 31 6th Test......................................... Test............................................................................................................... .......................................................................................................... .................................... 32 HYDRAULIC JUMP AND SLUICE GATE............................................................... .................................................................................................... ..................................... 32 Methodology..................................................................................................... ......................................................................................................................................... .................................... 32 Readings and calculations based on hydraulic jumps ......................................................... ....................................................................... .............. 33 33 Graphs ............................................................... ........................................................................................................................................ .................................................................................... ........... 36 Analysis and discussion ................................................................................................ ......................................................................................................................... ......................... 37 Recommendation.................................................................................................................................. .................................................................................................................................. 37 Appendix .............................................................. .................................................................................................................................... ................................................................................. ........... 40 References ........................................................... .............................................................................................................................. ................................................................................. .............. 39
INTRODUCTION The main objective of these laboratory experiments was to enable students to gain proper understanding of the theoretical knowledge about liquid flow throw various structures and elements such as weirs, venture flume, head loss and hydraulic jumps. The experiments were conducted in Hydraulics lab in the school campus. The following tests were conducted:
Broad crested weir
Sharp crested weir
Crump weir
Overshot weir
Venturi flame
This report will cover the apparatus used, the methodology and the results and discussion and analysis for all five tests.
WEIRS The simplest of definition of weir is that it is a barrier across a river or dam which is designed to change the flow characteristics. In most of the cases, weirs take the form of a barrier across the river that causes water wate r to pool behind the structure but allows water to flow over the top. Weirs are most frequently used to change the flow flo w of the river, preventing floods, and to measure discharge, Q, and to assist in rendering a river navigable. They allows engineers and hydrologists the simplicity in measuring the volumetric flow rate in small to medium sized streams since the geometry geometr y of the top of the weir is known and all water flo ws over the weir, the depth of the water behind the weir can be converted to a rate of flow.
1st Test BROAD CRESTED WEIR Broad crested weirs are solid structures that are generally constructed from reinforced concrete and usually span the full width of the channel. They are mostly used to measure the discharge of rivers and are much more reliable for this purpose than sharp crested weirs. The broad crested weir has the advantage that it operates effectively with higher downstream water levels than a sharp crested weir.
Apparatus used 1.
Hydraulics work bench
2. Weirs (broad crested weir) 3. Venture flume 4. Sluice gate 5. Recording sheet 6. Pen
Figure 1: Broad Crested Weir used during the experiment
Methodology I.
First begin by taking measurements of the broad crested weir (height) before inserting it in the flume
II.
Fill up the water storage tank of hydraulic bench with fresh and clean water
III.
Open the bypass valve to 50% position
IV.
Install the broad crested weir at the weir holding position
V.
Set the control valve to the fully open position
VI.
Connect the power supply for the water pump
VII.
Switch on the water pump; adjust the flow control valve to desired water flow rate using the Rota meter. For higher flow rate, the bypass valve should be completely closed
VIII.
Adjust the tail sluice gate so that the downstream water level is in a desired position
IX.
At a steady state flow, record the corresponding values such as water flow rate (Q) and depth of water (h).
X.
Finally, find the actual depth of water (h) by using height of water above crest – height of the broad crested weir
Figure 2: It shows the water flow using a broad crested weir
Recorded values and calculations based on broad crested weir
Run no
Q 3 (m /s)
B(m)
H(m)
H (m)
Cd
1
0.00067
0.079
0.039
0.00770188
6.46E-01
2
0.00083
0.079
0.043
0.00891667
6.91E-01
3
0.001
0.079
0.051
0.01151742
6.45E-01
4
0.00133
0.079
0.056
0.01325202
7.45E-01
5
0.00167
0.079
0.065
0.01657181
7.48E-01
Average
6.95E-01
3/2
Formula
Where: Q = Water flow rate Cd = Coefficient of discharge B = Channel width = 0.079m H = Height of water level above crest
Below is an example of calculation on finding Coefficient of discharge (Cd value) Run 1:
Therefore Cd value
Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using Broad crested weir
Broad crested weir 0.07 t s e r 0.06 c e v 0.05 o b a 0.04 l e v ) e H0.03 l r ( e t a 0.02 w 0.01 f o t h 0 g i e 0 H
0.0005
0.001
Water flow rate (Q)
y = 25.48x + 0.0228 R² = 0.9775
0.0015
0.002
From the graph; Height of water level above crest = 0.039 m Water flow rate = 0.000635(m 3/s)
Therefore;
Analysis and discussion The coefficient of discharge values were calculated using two different methods, one was calculated using the graph of height of water against water level and another was calculated using the values Cd values obtained from the recorded and calculated data and finding the average coefficient of discharge values. Both values were calculated using the same formula (i.e.
)
and as it can be noted that there is not much difference
between the average Cd value and the graphical C d value. The experimental value is 6.46x10-1 and the graphical value obtained is 6.12x10-1. This experimental uncertainty might have occurred due to time and limitations, the data were collected as single samples. All single sample experiments have some uncertainty that can attribute to the measured parameters. It also shows how accurately the experiment was carried out.
2nd Test SHARP CRESTED WEIR A sharp crested weir is made up of a vertical flat plate (usually made of metal plates) with a sharp edge at the top symmetrically located in a thin plate which is placed perpendicular to the sides and bottom of an open channel so that the liquid flows over the crest in order to drop into the pool below the weir. Sharp crested weirs come in many different shapes such as rectangular, v- notch and cipolleti weirs.
Apparatus used 1.
Hydraulics work beam
2. Weirs (sharp crested weir) 3. Venture flume 4. Sluice gate 5. Recording sheet 6. Pen
Figure 3: It shows the water flow in a sharp crested weir
Figure 4: Sharp Crested Weir water flow
Methodology I.
First, begin by taking measurements of the sharp crested weir (height) before inserting it in the flume
II.
Fill up the water storage tank of hydraulic bench with fresh and clean water
III.
Open the bypass valve to 50% position
IV.
Install the sharp crested weir at the weir holding position
V.
Set the control valve to the fully open position
VI.
Connect the power supply for the water pump
VII.
Switch on the water pump; adjust the flow control valve to desired water flow rate using the Rota meter. For higher flow rate, the bypass valve should be completely closed
VIII. IX.
Adjust the tail sluice gate so that the downstream water level is in a desired position At a steady state flow, record the corresponding values such as water flow rate (Q) and depth of water (h).
X.
Finally, find the actual depth of water (h) by using height of water above crest – height of the sharp crested weir.
Recorded values and calculations based on sharp crested weir
Run no
Q 3 (m /s)
B(m)
H(m)
H (m)
Cd
1
0.00067
0.079
0.023
0.00348812
8.23E-01
2
0.00083
0.079
0.028
0.0046853
7.59E-01
3
0.001
0.079
0.031
0.00545811
7.85E-01
4
0.00133
0.079
0.033
0.00599475
9.51E-01
5
0.00167
0.079
0.043
0.00891667
8.03E-01
Average
8.24E-01
3/2
Formula
Where: Q = Water flow rate Cd = Coefficient of discharge B = Channel width = 0.079m H = Height of water level above crest Below is an example of calculation on finding Coefficient of discharge (C d value) Run 1:
Therefore Cd value
√ Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using Sharp crested weir
Sharp crested weir 0.05 t s e r c e 0.04 v o b a 0.03 l e v ) e H0.02 l r ( e t a w 0.01 f o t h 0 g i e 0 H
0.0005
0.001
y = 17.89x + 0.0119 R² = 0.9427
0.0015
Water flow rate (Q)
From the graph; Height of water level above crest = 0.023 m 3
Water flow rate = 0.00062 (m /s)
Therefore Cd value
√
0.002
Analysis and discussion The coefficient of discharge values were calculated using two different methods, one was calculated using the graph of height of water against water level and another was calculated using the values C d values obtained from the recorded and calculated data and finding the average coefficient of discharge values. Both values were calculated using the same formula (i.e.
).
The experimental value obtained is 0.83 and the value obtained using
the graph is 0.76. There is a slight difference of 0.07. This experimental uncertainty might have occurred due to time and limitations, the data were collected as single samples. All single sample experiments have some uncertainty that can attribute to the measured parameters. It also shows how accurately the experiment was carried out.
3rd Test CRUMP WEIR A crump weir is most commonly used to predict or measure discharge in open flow channels. The cross-section of a crump weir can be of various shapes such as triangular, trapezoidal and rectangular and there slopes can be made to specific angles. In this laboratory test, the crump weir used was triangular in sharp. Since the crump weir is a fixed weir, the water flows over the weir without downstream level being below the weir crest and the discharge coefficient is nearly constant over a wide range of discharges.
Apparatus used 1. Hydraulics work beam 2. Weirs (crump weir) 3. Venture flume 4. Sluice gate 5. Recording sheet 6. Pen
Figure 5: shows the water channel flow through a crump weir
Methodology I. II.
Firstly, take measurements of the crump weir (height) before inserting it in the flume Fill up the water storage tank of hydraulic bench with fresh and clean water
III.
Open the bypass valve to 50% position
IV.
Install the crump weir at the weir holding position
V.
Set the control valve to the fully open position
VI.
Connect the power supply for the water pump
VII.
Switch on the water pump; adjust the flow control valve to desired water flow rate using the Rota meter. For higher flow rate, the bypass valve should be completely closed
VIII. IX.
Adjust the tail sluice gate so that the downstream water level is in a desired position At a steady state flow, record the corresponding values such as water flow rate (Q) and depth of water (h).
X.
Finally, Find the actual depth of water (h) by using height of water above crest – height of the crump crested weir.
Recorded values and calculations based on crump weir Run no
Q 3 (m /s)
B(m)
H(m)
H (m)
Cd
1
0.00067
0.079
0.031
0.00545811
9.11E-01
2
0.00083
0.079
0.033
0.00599475
1.03E+00
3
0.001
0.079
0.036
0.00683052
1.09E+00
4
0.00133
0.079
0.043
0.00891667
1.11E+00
5
0.00167
0.079
0.049
0.01084661
1.14E+00
Average
1.06E+00
3/2
Formula
Where: Q = Water flow rate
Cd = Coefficient of discharge B = Channel width = 0.079m H = Height of water level above crest
Below is an example of calculation on finding Coefficient of discharge (C d value) Run 1:
Therefore Cd value
0.911
Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using Crump weir
Crump weir 0.06 t s e r c 0.05 e v o b 0.04 a l e v ) 0.03 e H l r ( e t a 0.02 w f o 0.01 t h g i 0 e H 0
0.0002
0.0004
0.0006
0.0008
0.001
Water flow rate (Q)
y = 18.556x + 0.018 R² = 0.996
0.0012
0.0014
0.0016
0.0018
From the graph; Height of water level above crest = 0.031 m Water flow rate = 0.0007 (m 3/s)
Therefore Cd value
Analysis and discussion The coefficient of discharge values were calculated using two different methods, one was calculated using the graph of height of water against water level and another was calculated using the values Cd values obtained from the recorded and calculated data and finding the average coefficient of discharge values. Both values were calculated using the same formula (i.e.
).
The value obtained experimentally is 0.911 and graphically
was 0.952. There was a slight error of 0.04. This experimental uncertainty might have occurred due to time and limitations, the data were collected as single samples. All single sample experiments have some uncertainty that can attribute to the measured parameters. Also friction of the fluid may cause uncertainty. It also shows how accurately the experiment was carried out.
4th Test OVER SHOT WEIR Overshot weirs are designed for use in open-channel flows where upstream level control is required. When an over shot weir is applied in basic irrigation (open channel flow) it features the following capabilities;
intuitive control- changes in upstream water level are achieved with weir adjustments of the same amount and direction
precise control - increment or control with a stop log style of structure is limited by the depth of the flow
Inherent safety- the surge flows and debris pass over and carry on downstream
Apparatus used 1.
Hydraulics work beam
2. Weirs (over shot weir) 3. Venture flume 4. Sluice gate 5. Recording sheet 6. Pen
Figure 6: Water channel flow through over shot weir
Methodology I.
Firstly, take measurements of the over shot weir (height) before inserting it in the flume
II.
Fill up the water storage tank of hydraulic bench with fresh and clean water
III.
Open the bypass valve to 50% position
IV.
Install the over shot weir at the weir holding position
V.
Set the control valve to the fully open position
VI.
Connect the power supply for the water pump
VII.
Switch on the water pump; adjust the flow control valve to desired water flow rate using the Rota meter. For higher flow rate, the bypass valve should be completely closed
VIII. IX.
Adjust the tail sluice gate so that the downstream water level is in a desired position At a steady state flow, record the corresponding values such as water flow rate (Q) and depth of water (h).
X.
Finally, find the actual depth of water (h) by using height of water above crest – height of the over shot weir.
Recorded values and calculations based on crump weir
Run no
Q 3 (m /s)
B(m)
H(m)
H (m)
Cd
1
0.00067
0.079
0.03
0.00519615
5.53E-01
2
0.00083
0.079
0.034
0.00626929
5.68E-01
3
0.001
0.079
0.037
0.00711709
6.03E-01
4
0.00133
0.079
0.043
0.00891667
6.40E-01
5
0.00167
0.079
0.049
0.01084661
6.60E-01
Average
6.05E-01
3/2
Formula
Where: Q = Water flow rate Cd = Coefficient of discharge B = Channel width = 0.079m H = Height of water level above crest
Below is an example of calculation on finding Coefficient of discharge (Cd value) Run 1:
Therefore Cd value
√
Graph showing Height of water (H) against Water flow rate (Q) drawn from the values obtained using over shot weir.
Over shot weir
y = 18.649x + 0.0181 R² = 0.9971
0.06 t s e r c 0.05 e v o b 0.04 a l e v ) e H0.03 l r ( e t a w 0.02 f o t h 0.01 g i e H 0 0
0.0002
0.0004
0.0006
0.0008
0.001
Water flow rate (Q)
0.0012
0.0014
0.0016
0.0018
From the graph; Height of water level above crest = 0.03 m Water flow rate = 0.000638 (m 3/s)
Therefore Cd value
√
Analysis and discussion
The coefficient of discharge values were calculated using two different methods, one was calculated using the graph of height of water against water level and another was calculated using the values Cd values obtained from the recorded and calculated data and finding the average coefficient of discharge values. Both values were calculated using the same formula (i.e.
).
The experimental value obtained was 0.553 and the graphical value
was 0.526. There is a difference of 0.027. This experimental uncertainty might have occurred due to time and limitations, the data were collected as single samples. All single sample experiments have some uncertainty that can attribute to the measured parameters. It also shows how accurately the experiment was carried out.
5th Test VENTURI FLUME A venturi flume is a critical flow flume wherein the critical depth is created by a contraction in width of the channel. Thus the contracted section serves as a control. Venturi flumes have two advantages over weirs where the critical depth is created by a vertical constriction. First, the head loss is smaller in flumes than in weirs. Second, there is no dead zone in flumes where sediment and debris can accumulate; such a dead exist upstream of the weirs. A venture flume consists of three sections: a converging section, a throat section and a diverging section. The flow upstream and downstream of the throat is subcritical and supercritical respectively. A hydraulic jump forms in t he diverging section.
Apparatus used 1. Hydraulics work beam 2. Venture flume 3. Sluice gate
Figure 7: the venture flame used for this experiment
Figure 8: The water channel flow for the venturi flame experiment
Methodology I.
First, take measurements of the over shot weir (height) before inserting it in the flume
II.
Fill up the water storage tank of hydraulic bench with fresh and clean water
III.
Open the bypass valve to 50% position
IV.
Install the venturi flume at the weir holding position
V.
Set the control valve to the fully open position
VI.
Connect the power supply for the water pump
VII.
Switch on the water pump; adjust the flow control valve to desired water flow rate using the Rota meter. For higher flow rate, the bypass valve should be completel y closed
VIII.
Adjust the tail sluice gate so that the downstream water level is in a desired position
IX.
Finally, at a steady state flow, record the corresponding values such as water flow rate (Q) and depth of water (h).
Readings and calculations based on venturi flume Run no
Q
h
h1
bh1
Vth
E
m^3/s
m
m
m^2
m/s
m
Cd
1
0.00067
0.064
0.0416
0.001248
0.536859
0.05629
0.980804
2
0.00083
0.073
0.04745
0.001424
0.58307
0.064778
0.984223
3
0.001
0.08
0.052
0.00156
0.641026
0.072944
0.992369
4
0.00133
0.094
0.0611
0.001833
0.725586
0.087934
0.99718
5
0.00167
0.107
0.06955
0.002087
0.800383
0.102201
0.999281
Average
0.990772
Formula
Where:
Q = water flow rate Cd = Coefficient of discharge And given standing wave conditions as Z = 0, b = 0.03m, slope = 0%
Below is an example of calculation on finding Coefficient of discharge (C d value) Run 1: 1. Finding h1
2
2. Finding Area (bh1 (m ))
3. Finding Vth (m/s)
4. Finding specific energy, E (m)
5. Finding coefficient of discharge (C d)
Graph showing water depth (H) against Water flow rate (Q) drawn from the values obtained using Venturi flume.
y = 42.41x + 0.0369 R² = 0.9966
Venturi Flame 0.12
0.107 0.1
0.094
) 0.08 H ( h t p e d 0.06 r e t a W0.04
0.08 0.073 0.064
0.02 0 0
0.0002
0.0004
0.0006
0.0008
0.001
Water flow rate (Q)
0.0012
0.0014
0.0016
0.0018
From the graph; Water Depth = 0.064 m 3
Water flow rate = 0.000639 (m /s)
Therefore Cd value 1. Finding h1
2
2. Finding Area (bh1 (m ))
3. Finding Vth (m/s)
4. Finding specific energy, E (m)
5. Finding coefficient of discharge (C d)
Analysis and discussion
The coefficient of discharge values were calculated using two different methods, one was calculated using the graph of height of water against water level and another was calculated using the values C d values obtained from the recorded and calculated data and finding the average coefficient of discharge values. Both values were calculated using the same formula and same required. The experimental value obtained was 0.98 and the graphical value was 0.9685. This experimental uncertainty might have occurred due to time and limitations, the
data were collected as single samples. All single sample experiments have some uncertainty that can attribute to the measured parameters and also rounding off figures and fluid friction may also cause uncertainty. It also shows how accurately the experiment was carried out.
6th Test HYDRAULIC JUMP AND SLUICE GATE A hydraulic jump is a sudden rise in water/fluids level due to decreasing velocity. A hydraulic jump forms when a supercritical flow changes into a subcritical flow. The change in the flow regime occurs with sudden rise in water surface. Considerable turbulence, energy loss, air entrainment are produced in the hydraulic jump. A hydraulic jump can be used for mixing chemicals in water supply systems, for dissipating energy below artificial channel controls and can also be used as an aeration device to increase the dissolved oxygen in water. A sluice gate is a water channel that is controlled at its head by a gate. The sluice gate is used to regulate the flow of water and is made up to move up and down with the help of rollers fixed to the vertical plates. The formation and location of hydraulic jumps is controlled by a sluice gate at the upstream and a tail gate downstream of the jump .
Methodology
I.
First you begin by checking that the water level in the flume (with the pumps turned off) is just below the red tape on the piezometer at the flume outlet end. If the water level needs adjusting check with the TA.
II.
Turn on the pumps by first turning on the master power switch (whiteboard si de of the flume) and then hitting “run” on the three pumps (opposite side of the flume). The pumps should spin up to a reading of 30Hz, which means 1/2 (30/60) of full speed. Please do not adjust any of the pumps.
III.
The hydraulic jump should position itself around mid-flume. If after a minute or two it does not, the TA will help you position it.
IV.
Take measurements listed below in the “Data Collection/Analysis” section (hint: Use the Appendix to record your data).
V.
Observe the velocity as monitored by the acoustic Doppler Velocity meter (ADV) only in the subcritical section of the flow. This instrument measures the Doppler shift of sound to measure all three components of the velocity.
VI.
Record the average
u,
v and
w components of velocity and *Note: the ADV
measures 15 cm below the head of the instrument, and the head must be submerged when it is recording data; VII.
Do NOT mount the ADV closer than 15 cm from the bed. The ADV cannot be used in the supercritical section of the flow because the flow is too shallow.
VIII.
Before you turn off the flume, make waves in the supercritical and subcritical regions of the flow.
IX.
Finally, after you have taken all of your measurements, hit “stop” on the pump controllers (all three) and then turn off the master power switch.
Readings and calculations based on hydraulic jumps Description
Rate of flow Q(m3/s)
Water depth Y (m)
Area A (m2)
Velocity V (m/s)
Velocity Head (m)
Specific Energy, E (m)
Froude Number Fr
0.147
Distance along channel X (m) 0.66
Upstream sluice Downstream sluice Start of hydraulic jump End of hydraulic jump
1.67 x 10-3
0.01161
0.14380
0.00105
0.14805
0.11975
1.67 x 10-3
0.020
1.25
0.00158
1.05696
0.05694
0.07694
2.38621
1.67 x 10-3
0.035
1.58
0.00277
0.60289
0.01853
0.05353
1.02889
-3
0.085
2.17
0.00672
0.24851
0.00315
0.08815
0.27214
1.67 x 10
Where Cross section area, A = width of flume x Depth of water (Y) Velocity, V = Flow rate / Area Velocity Head = V2/2g Energy line = Y + V 2/2g
Froude Number =
Below is an example of calculations on finding Froude number (Fr value) Run 1 (upstream sluice) 1. Finding Cross section area (A) Cross section area, A = width of flume x Depth of water (Y) Cross section area, A = 0.079m x 0.147m Cross section area, A = 0.01161 m 2
2. Finding Velocity (V) Velocity, V = Flow rate / Area
3. Finding Velocity Head 2
Velocity Head = V /2g
4. Finding Energy line (E) Energy line = Y + V2/2g
5. Finding Froude Number (Fr) Froude Number =
√
Further Calculations 6. Discharge per unit width, q = Q / width of the flume
7. Critical Depth = ( q2/ g)1/3
) 1/3 8. Critical Energy = 3/2 x Critical depth
Graphs
Water Depth and Specific Energy against Distance along channel ) 0.16 m ( y 0.14 g r e n 0.12 E c i f i c 0.1 e p S d 0.08 n a ) m0.06 ( h t p 0.04 e D r e t 0.02 a W
Water depth Y (m) Specific Energy, E (m)
0
0
0.5
1
1.5
Distance along channel (m)
Graph showing Water Depth against Energy Line
2
2.5
Water depth against Energy Line 0.16 0.14 0.12 ) m 0.1 ( h t p e 0.08 D r e t a 0.06 W
0.04 0.02 0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Energy Line (m)
Analysis and discussion From the above graph of water depth and specific energy against distance along channel, critical depth was noted to be around 0.02m. The critical depth of 0.02m was then used to find critical energy using the second graph of water depth against energy line. The critical energy value was noted to be around 0.06m and in comparison with the calculated critical depth and energy, there is a slightly small difference between them. This may be due to experimental errors and also data uncertainty as all the data was collected as single samples.
Recommendation
Recommendations for fellow students who are going to do this experiment are to repeat the experiment more than once so that the average reading can be taken which i s more accurate. Ask more than one class mate to record the readings to avoid errors. Also, while performing the experiment, more than one class mate should carry out the tasks so that the different approaches will show the results observed and the variables recorded. Noise should be kept to a minimum while in a laboratory and always listen to the instructor. If any guide lines are needed, then refer to t he supervisor Errors can never be ignored when it comes to laboratory work. The aim is to reduce the error as much as possible to obtain accuracy in work. Ways to reduce the error are by repeating the experiment for three times or more and then taking the average readings, by being extra cautious during the experiment, by asking more than one person to record the readings and carry out the experiment, etc.
RULES OF LABORATORY HEALTH AND SAFETY Lab. Rules
1,No running, jumping, horseplay, drinks, food and smoking are allowed in the laboratory. 2,Users must adhere to safety procedure of the laboratory. Housekeeping
Clean the work area and return all tools after use. Safety conscious 1,Always stay alert 2,Wear safety goggles when required. Dry up wet floor 1,Floor should be kept dry at all times. 2,Water on the floor must be swept away immediately. Keep water level within safety limit 1,Water level inside the flume/water related equipment must not rise beyond the safe level. 2Users to look out at all times in case water hose falls off or water overflows from flume/water related equipment.
Gloves and rubber gloves Wear safety gloves when handling metal sheet/ toxic chemicals. Power extension All extension cords must be secured above ground level. Barricades and guard rails All floor openings must be barricaded and warning sights posted. Equipment Seek approval from staff before using any piece of machine/equipment.
References Chadwick, A Morfett, J and Borthwick, M ( 2004) Hydraulics in civil and environmental engineering . 4th edn. London: E & FN Spon Press Hamill, L (2011) Understanding hydraulics. 3rd edn. Basingstoke: Palgrave Macmillan.
Marriott, M. (2009) Nalluri & Featherstone’s civil engineering hydraulics. 5th edn. Oxford: WileyBlackwell Al Naib, S. K. (1997) Experimental fluid mechanics and hydraulic modelling. London: University of East London
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