Hot jet

Mahdi

hello.., I am trying to model a hot subsonic jet (M_J=0.75 T_J=600K, A2/A1=0.31), nozzle is very simple one, and was working properly for cold jet. The problem I have already faced is that it diverges after some iterations! I have put pressure inlet BC for jet inlet, and Pressure outlet for sorrounding meduim. I suspect the magnitude of stagnation and supersonic pressure defined for BC of inlet and outlet pressure. Could someone give me a hand and tell me what could be the problem? as I said I worked with this geometry once for a cold jet and got good results (the only difference was that, I used velocity inlet for jet inlet as the flow was cold). THANKS Mahdi