I've got a relatively length heat transfer simulation I'm working with.  I wondered if perhaps I could initiate some flow freezing to speed things up.

I get a warning "that Flow Freezing may cause problems" followed by a comment "Maximum Mach Number = 0.3142"

What interaction is there between Flow Freezing and Mach Number?  Are they just indicating that because temperature effects on fluids plays such a large role in determining Mach Number that it might prevent accurate convergence?

I can't find anything in the help files that links Flow Freezing and Mach Number.