Turbulence model for Transient Pipe Flow Modeling

Brian

Concerning transient modeling of a high pressure blow-down and supersonic flow in small diameter tubes (approx 0.5 inch), has anyone found a way to overcome the extremely small timesteps required by high speed flow with a fine grid?

Has anyone had good sucess with a particular turbulence model for problems of this type?

This is a very highly turbulent flow problem. The pressureization is coming from a pyrotechnic charge that pressurizes a chamber up to 10,000 psi and then vents to ambient pressure. Any recommendations for K, e in the high pressure tank?

I'm running Fluent V 6.0

thanks