Hydraulic Laboratory Report – Water Surface Profile in Open Channel Flows

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Aim The aim of this experiment is to model a hydraulic jump in an open channel. Water surface profile will be measured, including flowing over a broad crested weir, forming a super-critical gradually-varied flow, the subsequent hydraulic jump and then the sub-critical gradually-varied flow. Theoretical predictions will be given based on numerical calculation by using the graduallyvaried flow equation for the sub- and super-critical flow profiles. Then, the comparison of these two results will be given. Method 1. A rectangular flume of 110cm long and 7.7cm wide is used where recirculating flow enters the flume under a sluice gate. The flow is controlled to maintain a constant head. A hydraulic jump will occur in the downstream of an obstruction and super-critical gradually-varied flow. The set-up prepared by demonstrator is shown in Figure 1. The profile sketch is shown in Figure 2. Figure 1 Set-up Figure 2 Profile of flow in the flume 2. Estimate the inflow rate by measuring the height of the water at the control points. Compare it with the reading on the flowmeter. 3. Measure the slope of the flume. A measuring tape is used to obtain the distance of two chosen points and their height above the ground. 4. Use a set square ruler to measure the water level profile and a pointer gauge for more precise measurement near the hydraulic jump. The increments of these reference points should be less than 2cm. 5. Use Euler method to plot the water surface profile from control sections. Use Heun’s Method with and without iterative improvement and compare the results of the two method. 2 Results 1. The slope of the flume Table 1 Data for calculating slope Point 1 0 1165mm Location along the flume Height from ground Slope of the flume 0 = Point 2 640mm 1162mm (1165 − 1162) ℎ = = 0.00469 √(640 − 0)2 + (1165 − 1162)2

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