Viscosity -- from Eric Weisstein's World of Physics

This entry contributed by Leonardo Motta

The viscosity of a fluid can be defined as the measure of how resistive the fluid is to flow. It is analogous to the friction of solid bodies in that it also serves as a mechanics for transforming kinetic energy into thermal energy.

Given two plane parallel plates separated by a distance d and with a fluid between them, keep one stationary while moving the other at a slow speed . A common situation is that the force F required to keep the second plate moving is proportional to its area A and to . A fluid in which these quantities are proportional, called a Newtonian fluid, therefore exhibits shear stress proportional to , giving

Here, is a constant for the given fluid called the dynamic viscosity.

Bulk Viscosity, Dynamic Viscosity, Eddy Viscosity, Kinematic Viscosity, Navier-Stokes Equations, Newtonian Fluid, Poise, Second Viscosity Coefficient, Shear Viscosity

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