We have so far considered ideal fluids, which are not only incompressible but also nonviscous. In the absence of viscosity, mechanical energy is conserved, which is the essence of Bernoulli's equation. However, to understand one of the more important properties of a fluid, its ability to exert drag forces on objects, we must go beyond the nonviscous approximation and incorporate the effects of viscosity into our description of fluid flow.

- Viscosity
- The stress tensor and the Navier-Stokes equation
- The Reynolds number
- Fluid flow at low Reynolds number
- Viscosity effects at high Reynolds numbers

Sun Sep 28 22:13:11 EDT 1997