always disconvergent
 

hello,everyone. I was simulating the flowfield of supersonic crossflow and normal sonic jet. The configuration was a 2d plate,
By using 1st scheme of flow in FLUENT, I can get the convergent solution. however, when the 2nd SOU scheme was applied, the calculation always unstable.
Please give some advise, thank you very much.

Have you tried to lower the under-relaxation factors?

yes, I have lowered under-relaxation factors from the default value(0.8) to 0.5, it failed still.
the boundary condition:
crossflow: pressure inlet(supersonic) p0=2.4e5 Pa, T0=309K, M=3.5
jet: pressure inlet(sonic): p0=3.8e5 Pa, T0=293K,
upper boundary: farfield pressure: M=3.5, T=86.5K
out: pressure outlet: p=3145 Pa.

Just decrease the under-relaxation factors more ..... I had problems with under-relaxation of 1/3 or less of default values

I tried the value of under-relaxatioin factors of 0.1, it didn't work. I observed the field, when I turned 1st scheme to 2nd scheme, after several iteration, there was high temperatrue region right behind the mach disc of jet plume.
I think it was the source of disconvergence.
But I don't konw how to deal with this problem

okay .... have you checked the mesh in this region?

yes, mesh is very simple, it is H-type, I think the problem should not lie in mesh.
Now I am trying calculating with pressure-based solver instead of density-based solver.

You should use density based solver for compressible flows. Have you tried decreasing the courants number?