Low Reynolds Number Flow

We have seen earlier that Reynolds number is the ratio of inertia force to viscous force. For flow at low Reynolds number, the inertia terms in the Navier-Stokes equations become small as compared to viscous terms. As such, when the inertia terms are omitted from the equations of motion, the analyses are valid for only Re << 1. Consequently, this approximation, linearizes the Navier-Stokes equations and for some problems, makes it amenable to analytical solutions.

In the next two slides we will discuss such flows. Motions at very low Reynolds number are sometimes referred to as creeping motion.