Hi everyone While using density solver,I keep getting the message "time step reduction in -- cell" , everytime I switch from first to higher order discretization while simulating supersonic combustion flow. There is only a temporary improvement if I reduce the Courant No. Can anyone Plz tell me why this message appears and how to get rid of it....because the results become absolutely erroneous after the message. Thanx ALI

I have been told that the core numerics of FLUENT 6.3 does produce errors when you change from lower to higher order discretization schemes. In FLUENT 12, a new algorithm has been introduced that slowly blends the formulation from first order to second order schemes. It may not be the same problem that you are facing right now, but you might want to try out the FLUENT 12 Beta version and see if your problem can be solved.

Hope that helps.