Hi Would you please tell me which turbulent model (in the viscous panel of fluent program) should I choose for highly internal compressible flow, for example for a gas flow through a pipe under high pressure gradient?

Plz explain compelet mach number? do you want model combustion? its dependent your problem

Well actually i'm modelling the flow of very high pressure gas in a tube which it the mach number shouldn't be above 1. The gas is stagnant in a vessel and then accelerate through the pipe to the atmosphere. The pressure ratio is almost 300 with no combustion. Thanks a lot

Hi Then you use K-epsilon Model Its suiteble for your problem. Mesh generation is important in Wall treatment. Good luck