I am trying to simulate an supersonic jet and compare it with experimental results uses shadowgraphy. How can I produce a 'numerical schliren' for comparison? Is is the density derivative?

Shuo

For supersonic jets the literature gives the exit pressure ratio Pe/Patm and the exit Mach number. If I am doing numerical simulation i also need the density ratio rho_e/rho_atm. How can I estimate this?

Try to search the forum - I'm sure I've seen the procedure to get "numerical schliren". Probably it was Star-CD forum, not the main one.

I read that some papers that plotted the log(base 10?) of density gradients. I wonder what direction the density gradient is in x, y?