Question

How is Reynolds number defined as?

(a) Ratio of pressures in the inlet to the outlet of a pipe

(b) The product of velocity of the flow and the diameter of the pipe, divided by the kinematic viscosity of fluid

(c) The product of density of the fluid, velocity of the flow and the diameter of the pipe, divided by the dynamic viscosity of fluid

(d) Ratio of inertia force to viscous force

I had been asked this question in final exam.

Origin of the question is Flow of Viscous Fluid Through Circular Pipes topic in section Viscous Flow & Turbulent Flow of Fluid Mechanics

Answer 1

Correct choice is (d) Ratio of inertia force to viscous force

To explain: The question demands the definition and not the commonly used formula of Reynolds number. Some of them denote the formula of Reynolds number. The definition of Reynolds number is the ratio of inertia force to viscous force in a pipe flow.