Water flows from reservoir A through a pipe of length 250 m and diameter 0.1 m at a velocity of 1 m/s as shown in Figure 6. A valve is installed at the outlet B. The valve can be operated in 2 modes: instantaneous closure or closure in finite time. For instantaneous closure, it can be completely closed or partially closed to reduce the flow velocity in the pipe to 0.4 m/s. For closure in finite time, the valve is closed in 1 second. In this mode, the closure can be complete or partial too, where the flow velocity is also reduced to 0.4 m/s. The speed of the pressure waves in the pipe is 1250 m/s. If the maximum allowable stress for the valve is 0.4 MPa, suggest ways to operate the valve to avoid valve failure. You may assume that the valve failure is caused solely by water hammer pressure. The density of water is 1000 kg/m. For instantaneous valve closure, water hammer pressure is: Ph = Pcp (V - V) For rapid valve closure, water hammer pressure is: Ph For slow valve closure, water hammer pressure is: Ph pcp (V - V) 2L/Cp tc - Pn = A Il Figure 6 valve (10 marks)