Hi, How do I determine the CFL number for an explicit hypersonic problem? Is there any book or paper?

Thanks, Subramani

Hello For explicit problems, your CFL number should not be greater than 1, for stability reasons. Altough that depends on how complicated is your geometry, time marching scheme, etc. Try using CFL=1 for start in order to allow a maximum time step (to accelerate the convergeance). If it's instable, try lowering a little, 0.8..0.9. or use under relaxation. The best way in my oppinion is to begin with a CFL < 1, let's say 0.8, and after that switch to CFL=1.