Fluid Mechanics and Hydraulic Machinery Miscellaneous
 Which one of the following is NOT a rotating machine?

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NA
Correct Option: C
NA
 A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as 990 kg/m^{3}. The isentropic specific work done by the pump in kJ/kg is

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Work done by pump = υ(p_{2} – p_{1})
= (30  1) × 100 990
= 2.93 kJ/kgCorrect Option: D
Work done by pump = υ(p_{2} – p_{1})
= (30  1) × 100 990
= 2.93 kJ/kg
 Water flows through two different pipes A and B of the same circular crosssection but at different flow rates. The length of pipe A is 1.0 m and that of pipe B is 2.0 m. The flow in both the pipes is laminar and fully developed. If the frictional head loss across the length of the pipes is same, the ratio of volume flow rates Q_{B} /Q_{A} is _____ (round off to two decimal places)

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NA
Correct Option: A
NA
 Water (density = 1000 kg/m^{3}) at ambient temperature flows through a horizontal pipe of uniform crosssection at the rate of 1 kg/s. If the pressure drop across the pipe is 100 kPa, the minimum power required to pump the water across the pipe, in Watt, is _______.

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W = m v(P_{1}  P_{2})
W = 1 × 1 100 × 10^{3} = 10 Watt 1000
Correct Option: A
W = m v(P_{1}  P_{2})
W = 1 × 1 100 × 10^{3} = 10 Watt 1000
 For steady, fully developed flow Inside straight pipe of diameter D, neglecting gravity effects, the pressure drop ∆p over a length L and the wall shear stress τW are related by

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Shear stress on wall,
τW = δP . R δx 2 where δP . ∆ δx L & R = D 2 ∴ τW = ∆P × D = ∆PD L 2 x 2 4L
Correct Option: A
Shear stress on wall,
τW = δP . R δx 2 where δP . ∆ δx L & R = D 2 ∴ τW = ∆P × D = ∆PD L 2 x 2 4L