DISCUSSION

After we have done this experiment, we are able to determine the flow rate and the coefficient of discharge for flow over a triangular and rectangular notch using the Basic Weir apparatus. We can make a few discussion based on this experiment.Firstly, from the result we get, we observed that the trend of the coefficient discharge for rectangular are increasing. We get the average of coefficient discharge is 0.03 m3/s. So the results we get are suitable because the most ideal volumetric flow rate for a rectangular notch is 0.021m3/s and above. For rectangular notch, Cd values at lower flow rates were in quite wide variations. This was because the difference of values of height was in wide range. Secondly, For V-notch, Cd values at low flow rate were not in wide variations. This is because the low height increments.

For experimental values for Cd for water flowing over V-notch with central angles varying from 100 to 900. The rise in Cd at heads less than 0.5 ft is due to incomplete contraction. At lower heads the frictional effects reduce the coefficient. At a very low heads, when the nappe clings to the weir plate, the phenomenon can longer be classed as weir flow.

The values of Cd for vee notch at low flow rate were not in wide variations because the low height increments.

But the values of Cd for rectangular notch at lower flow rates were in quite wide variations because the difference of values of height was in wide range.

From the experimental result, the values of coefficient discharge calculated increased when the head increased for rectangular notch. From the theory, volume flow rate that is suitable for this notch is about from 0.021m3/s and above, but in the experiment we cant constant the value of volume flow rate. We only know the volume flow rate by measuring the data that we have. So the volume flow rate that we use less than the volume flow rate of theory because of that the values of Cd also less from the theory.

CONCLUSIONWhat we can conclude after we have done this experiment, our objectives are to observed the characteristic of open-channel flow over, firstly, a rectangular notch and then a triangular (vee) notch and to determine the discharge coefficient for both notches.

We have also concluded that the coefficient of discharge of both; triangular and rectangular notch depends on the volumetric flow rate of the water and the height of the water level from the base of the notch. The coefficient of discharge corresponds differently to the height of the water level (H) to the type of notch used. For rectangular notch; H3/2 and triangular notch; H5/2 in there has given equation. For triangular notch, the coefficient of discharge also depends on the angle of the vee shape. Rectangular weir has wide range variations of Cd. This is because this notch has width with 0.03 m.

V-notch has small range of variations for the value of Cd. This is because this notch has an angle at its bottom where about 90o. This angle might affect the values of flow rate and Cd.

The Cd values for both notches.

Rectangular NotchTriangular Notch

10.020.008

20.030.0096

30.030.009

40.040.012

50.040.013

RECOMMENDATIONS

1. The data that was observed in the experiment that was time gain should be taken twice. This can avoid the very wide deviation because of only take once of each observation

2. Take care not to allow spillage to occur over the plate top adjacent to the notch. If this happened, it would effect the collection of known volume.

3. Once the data were taken, the procedure cannot be reverse to find the value of time collection by adjusting the height. This would affect the value of height datum. The height datum must be constant and the observation should be done once round for the little increment of height especially for V-notch.

4. The readings of height should be taken carefully by avoiding sight error. The time collection should be taken much appropriately.