Intuitive Derivation of Reynolds Number

Abstract

It is evident from the literature that many engineers describe the Reynolds number qualitatively as ``the ratio of inertial forces to viscous forces''. Yet it is not immediately obvious that the well known expression Re = LV(rho)/(eta), which involves the size L of a solid object moving with speed V relative to a fluid of density rho and viscosity eta--is in fact a ratio of forces. It is hoped that the following treatment, which is based on an energy rather than force perspective, will help to de-mystify the important parameter given to us by Osborne Reynolds