Supplementary Material 6.5

Chapter 6 – Air Valves

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Surge Analysis and the Wave Plan Method

Supplementary Material: Example Problems and Solutions

Chapter 6 – Problem 6.5

6.5 Consider an air valve venting air out of a 500 mm internal diameter pipeline similar to that shown in Figure 6.13. The celerity of the pipe sections on both sides of the air valve is 1200 m/s. The water flowrate at time = t in the pipe section to the left of the air valve Q1 = -0.3 m3/s and in the pipe section to the right of the air valve Q2 = -0.15 m3/s. At time = t, a pressure wave of magnitude ∆H1 = 3m arrives at the air valve from the left side of the air valve and another pressure wave of magnitude ∆H2 = 5m arrives from the right side. If the residual pressure head (H1) at the air valve location at time t is 0.1m, and the air valve float closes within a short time interval ∆t after releasing the remaining air (time = t+∆t), compute the slam pressure associated with the rapid reduction in flowrate arising from the lifting of air valve float.

Solution:

Based on Eq. 6.24, the slam pressure H3 = 148.27 m


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