GATE Exam Questions - Engineering

Q1:

The flow of water (mass density = 1000 kg/m3 and kinematic viscosity = 10-6 m2/s) in a commercial pipe, having equivalent roughness ks as 0.12 mm, yields an average shear stress at the pipe boundary = 600 N/m2. The value of ks/δ' (δ' being the thickness of laminar sub-layer) for this pipe is

A 0.25

B 0.50

C 6.0

D 8.0

ANS:D - 8.0

Laminar sub-layer thick = 11.6 * kinematic viscosity/shear velocity.

Shear velocity =(shear stress /density of fluid)^0.5.