[pawank]

This is about explicit, 3D, compressible NS solver. Consider two cases:
1) Code diverges after n time steps with step size dt. When I reduce the time step to 0.1*dt, the code diverges after 10*n time steps. i.e. code blows at the same actual time.
2) Code diverges after n time steps with step size dt. When I reduce the time step to 0.1*dt, the code still diverges after n time steps.

Which of the cases indicate a problem in CFL condition/numerical instability? What does the other case indicate? Or is it that either of the cases don't indicate anything specific, and there can be multiple possibilities where the problem is?

Thanks