Fluid Dynamics is the study of fluids in motion. The basic equations governing fluid motion have been known for more than 150 years and are called the Navier-Stokes_equations which govern the motion of a viscous, heat conducting fluid. Various simplifications of these equations exist depending on which effects are insignificant. There are several dimensionless parameters which characterize the relative importance of various effects. Some of these are Mach number, Reynolds number and Prandtl number.