Hi all, I have a supersonic compressible flow and am using a UDF to define the the total pressure at the inlet. I started by ignoring the Supersonic/initial gauge pressure and got a result which looked wrong. I then changed the initial(static) pressure to the same as the total pressure and get an error after a few time steps. Any ideas or experience with this sort of problem would help a great deal. Thanks.

In case steady state, For example,give Total Pressure = 50bar/5000000pa and initial static gauge pr = 49bar/4900000pa. [Gauge pr = absolute pr - 1 ] Then, start with low underrelaxation and increase it for the convergence.

In case of transient, write udf for both Total pr and initial static gauge pr. with respect to time. and reduce the time step to very low (depending on geometry,complexity of flow, mesh )

Regards, M K P