The fresh water intake in a reservoir has a cross-sectional area of 0.800 m2 and receives water flowing at a speed of 0.500 m/s. At the outlet, a vertical distance of 200 m below the intake, the cross-sectional area is 0.020 m2. Calculate the pressure difference between the inlet and outlet.
Area of cross section at inlet = Ai=0.8 m2
velocity of flow at inlet=Vi=0.5 m/s
Flow rate =Q= 0.8*0.5=0.4 m3/s
cross sectional area at outlet =Ao= 0.02 m2
velocity of flow at outlet = Vo=0.4/0.02=20 m/s
Let elevation of inlet=hi
Elevation of outlet =hi-200
Let pressure at inlet be Pi and pressure at outlet be Po
Let us apply Bernoulli's equation to determine the pressure difference between inlet and outlet
Pi+ghi+0.5
vi2
= Po+
gho+0.5
vo2
Or, Pi+1000*9.8*hi+0.5*1000*0.52 = Po+1000*9.8*(hi-200)+0.5*1000*202
Pi-Po =1000*9.8*(hi-200)+0.5*1000*202 - (1000*9.8*hi+0.5*1000*0.52 )
= -1760125 N/m2
Pressure at inlet is lower than pressure at outlet and the pressure difference is 1760125 N/m2
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