Question

For flows over a flat plate, at length scales near to the length of the flat plate, which of these is correct?

(a) Inertial force is zero

(b) Inertial force is large

(c) Inertial force is equal to viscous force

(d) Viscous force is large

I had been asked this question during a job interview.

This intriguing question originated from Turbulent Boundary Layer topic in section Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Correct choice is (b) Inertial force is large

To explain I would say: Reynolds number depends on the length scale taken for the calculation. At the length scales near to that of the length of the flat plate, the Reynolds number will be high. Therefore, the inertial forces will be large.