5.Discussion: Over all experiment was significant success except there were some minor errors when these results were plotted on the graphs those could be as a result of setting time difference or different reading of the heights. Again those errors probably due to lack of concentration, and also. Some times may have been recorded wrongly and the height over the head may have been noted wrongly.
6.Nomenclature
is the actual discharge over the weir
is the theoretical discharge over the weir
Cd is coefficient of discharge
H is the head of the weir in meter
V is the volume of water in litre
T1 is the first time taken in sec
T2 is the second time taken in sec
Tmean is the average time of T1 and T2
H^1.5 is the H when read it to the power of 1.5
B= 32 mm
P= 76 mm
W= 248 mm
Vernier Scale Direction of the water flow
Drain plug Release
Tank
Pump Head U Notch Weir
Manometer
Power on/off
EXPERIMENT: CALIBRATION OF A SHARP-CRESTED WEIR
U-notch Sharp-Crested weir discharge formula:
Measure width of crest, B (m). B =
Procedure
- Pump sufficient water into the channel behind the weir so that it just flows over the weir.
- Close the pump valve and let the flow over the weir come to a stop.
- Set the depth gauge to the water surface– this is the reading to the weir crest (i.e. H = 0) - and set the vernier scale to read zero.
- Set the pump so that the head H has its maximum permitted value.
- Let the system settle, i.e. wait for H to become constant.
- Read and record the value of H.
- Time the collection of a known volume of water, say 10 litres, and record the time.
- The discharge rate is then calculated as:
Q = volume collected / time taken (units are m3/s.)
- Now vary the head H in steps of about 5mm over its whole range and at each setting of H measure and record H and Q.
The discharge equation for the U-notch weir is: (m3/s)
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For each flow setting calculate: H(m), H3/2, Qactual (m3/s), Qtheory (m3/s), and Cd
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Plot the Stage-Discharge Curves, i.e. plot Qactual against H, and Qtheory against H
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Plot Cd against H. Take the Cd from (5) below and plot as a horizontal line here.
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Plot Qactual against H3/2 and show that the points fall on a straight line through the origin i.e. point (0,0).
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Plot Qactual against Qtheory and show that the points fall on a straight line through the origin i.e. point (0,0). The slope of the best-fit straight line through the points will give directly a best estimate of the mean value of Cd over the range of conditions used in the experiment: this will be a weighted-mean
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Quote the best discharge equation for the weir as with Cd replaced by its best numerical value (found from 5 above).
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Quote the discharge relationship for this weir in its simple
Evaluate the lab experiment
I strongly believe this laboratory components were excellent learning tools for reinforcing my fluid mechanic lecture materials because I had to work through out some operations in order to obtain some meaningful results and then apply theoretical data to a practical as to design a floating crane based on a small pontoon experiment.
This operation was among group of more than ten students. We were a newly formed group with no experience of one another but I learnt a lot about myself and my ability to work in an unfamiliar situation like this.
My part was essential and had to be so accurate. This is involved reading setting and concentration on my readings so accurately. We openly encouraged to talk among ourselves, to discuss our result and conclusions, but at the same time be responsible for each own work because a small error could have a huge impact on our results.
This task has made me to be more aware for every stage of report that I will do in my future. Highlighting the importance of small aspects has been one of the main influences on me. This gave me a better idea of how to undertake the task such as a lab report and what exactly to consider. I personally feel that this lab report would have a greater impact on me towards any other report that I will in the future.
I must also admit that something was definitely lost in rushing as a result of a lot of pressure as the task contained a lot of demands and this made to move through each stage quite rapidly In order to get the task done.