Does anybody know the reason why the solution starts to blow up over Ma 9 during iteration ?

I am using time marching Mac Cormack method and changed only free stream velocity as Ma increases.

It was possible to get stable solution by decreasing time step arbitrarily but there existed the limit.

At Ma 25 , the target, the solution blew up however small I set up the time step.

Have a good day, you all.

flow variables jump more as Ma increase. If your numerical scheme rely on numerical viscosity to smooth this jump, it means needing larger viscosity.

Thanks a lot, versi~