Density UDF for supersonic flow
 

I want to model non-ideal gas supersonic gas flow. I have written UDF routines for the density and the sound speed. They calculate for a short while, but then diverge and crash (even using the ideal gas equations in the UDF). If I use Ideal Gas density (not UDF routines), the calculation is fine. With the UDF for the density, Fluent no longer seems to know that it is supersonic. Any suggestions on how to get the case to run?