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-   -   CFL for explicit hypersonic problem (https://www.cfd-online.com/Forums/fluent/46431-cfl-explicit-hypersonic-problem.html)

Subramani Sockalingam October 28, 2007 09:20

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

Thanks, Subramani

Ervin Amet October 29, 2007 05:05

Re: CFL for explicit hypersonic problem
 
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.


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