Water at 20oC (viscosity = 1 cp) flows through a smooth straight pipe A of inside diameter 4 cm at an average velocity of 50 cm/sec. Oil flows through another pipe B of inside diameter 10 cm. Assuming similarities, calculate the velocity of oil through pipe B. Specific gravity of oil is 0.8 and its viscosity is 2 cp.
Data:
A:
Dia of A = 4 cm
Velocity of fluid in A = 50 cm/sec
Density of fluid in A = 1 g/cc
Viscosity of fluid in A = 1 cp
B:
Dia of B = 10 cm
Density of fluid in B = 0.8 g/cc
Viscosity of fluid in A = 2 cp
Formulae:
For dynamic similarity, ratio of forces to be equal
Inertial forceA / Inertial forceB = Viscous forceA / Viscous forceB
i.e. NReA = NReB
Calculations:
NReA = NReB
Therefore,
4 x 50 x 1 / 1 = 10 x VB x 0.8 / 2
200 = 4 VB
VB = 200/4 = 50 cm/sec
Velocity of oil through B = 50 cm/sec
Last Modified on: 04-Feb-2022
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