This example contains a sim file that are set up to run hypersonic conditions in STAR-CCM+.
Above around mach 8.0, typical supersonic flight envelopes begin to change into hypersonic regimes. These are quite different cases to run, and require different best practices for setup and running...
The below practices have seen some good successes with these cases, but it is important to note that these settings and processes may not be necessary or sufficient for all cases involving hypersonic flows..
It is advisable to try and converge using the MUSCL 3rd order scheme with the AUSM+ flux scheme. At times it may be needed to start with lower order and then change to the higher order after some level of convergence is achieved.
Staring with a turbulence model can cause divergence in some cases. In the event that this occurs, running the case inviscid for a good while until convergence is achieved has helped. You can then restart with a full turbulent physics setup (if required, sometimes an inviscid solution is sufficient at these speeds).
If turbulence is used, the suggested turbulence models are the K-Omega SST with a1 = 0.355 (there is a 2013 NASA paper on that shows that this is the best a1 coefficient for shock separated flows) and QCR (quadratic) as the constitutive option.
Specified k and omega explicitly in initial conditions and in regions - k = 1E-6 * Uinf^2 and omega = 5*Uinf/ (mean aerodynamic chord or characteristic length).
In these regimes, ideal gas may not be the appropriate equation of state, real gas equilibrium may be a better option. It does not model the individual dissociation of species that can occur at these flight envelopes, but it does model the material properties that are applicable due to dissociation here.
The associated gas material properties: Sutherland model for the viscosity, equilibrium air properties for the specific heat and the speed of sound, and constant values for the other properties.
Reducing the AMG solver tolerance to 0.001 may be helpful in convergence of difficult problems.
Use of the ILU underrelaxation method has been shown to help in hypersonic flight envelopes.
Grid Sequencing Initialization can be helpful as well, and use the Automatic CFL method for the coupled solver in these cases. For difficult cases using the Line Search underrelaxation may also be helpful rather than a constant value.
Use a CFL of between 1 and 3 for the grid sequencing, rest of the settings leave as defaults
The default limits for minimum pressure in the coupled solver and min/max temperature limits in the reference values are respectively: 1000 Pa, 100 K, and 5000K.
For most cases these values are quite reasonable limits, for hypersonics they are often not. Absolute pressures of 10 Pa can be seen, as can temperatures rising to in excess of 10000K.
So we often must change these limits to be sure we are dealing with physical reality of these extreme conditions.
An inviscid setup sim file will be attached in a clean (no mesh, no solution) state.