Question

The critical Reynolds number varies from ________ for validity of Darcy’s law.

(a) 0.1-75

(b) 75-100

(c) 100-175

(d) 175-200

This question was posed to me in a national level competition.

This intriguing question comes from Permeability in portion Permeability of Geotechnical Engineering I

Answer 1

Correct choice is (a) 0.1-75

For explanation: The Reynolds number is the ratio of inertia to viscous forces. For the validity of Darcy’s law, the critical Reynolds number varies from 0.1-75. The critical Reynolds number is the condition when the flow changes from laminar to turbulent flow.