Question

The superficial velocity in a stratified bed is equal to __________

(a) Terminal settling velocity

(b) Terminal settling velocity * porosity

(c) Terminal settling velocity * (porosity)^2

(d) Terminal settling velocity * (porosity)^4.5

The question was posed to me in an international level competition.

This intriguing question comes from Filtration Hydraulics topic in portion Filtration of Environmental Engineering

Answer 1

The correct choice is (d) Terminal settling velocity * (porosity)^4.5

For explanation: A stratified bed having a non uniform sized particles are completely fluidized when for the largest particle, the superficial velocity v = vs * e^4.5  where vs is the terminal settling velocity and e is the porosity.