Question

Which of the following represents the correct relation between displacement velocity and diameter of the particle?

(a) v1 = (8Bg (G-1) d/f) ^1/2

(b) v1 = (8Bg (G-1) d2/f)^2

(c) v1 = (8Bg (G-1) d/f)

(d) v1 = (8Bg (G-1) d/f)^2

The question was posed to me during a job interview.

My question is taken from Theory of Sedimentation in section Sedimentation of Environmental Engineering

Answer 1

The correct answer is (a) v1 = (8Bg (G-1) d/f) ^1/2

For explanation: Displacement velocity is given by v1 = (8Bg (G-1) d/f)^1/2 where B is a constant with value range 0.04-0.06, G is specific gravity, d is the diameter of the particle and f is the Darcy Weisbach friction factor.