Hi, Im currently analysing the flow through a diffuser. I have developed a hex mesh for the same. The boundary conditions are 650 kg/s mass flow and 18000 Pa inlet total pressure. Initially i tried BC's of inlet mass flow and outlet static pressure but the solver exited with a "High Mach Number" at the inlet. I then tried a inlet total pressure and outlet static (giving a low value of static pressure to begin with) but the solver exits after around 200 iterations with the same error. I have also tried using a low physical timescale but with no avail. Couls someone please suggest a solution to this problem. Thanks in advance.

Luke

Luke

Start with simple convergent-divergent nozzle with a slower speed using total pressure inlet and static pressure outlet conditions. Try low order first then move to high order. Let it run for long enough. Ramp the speed up when it starts solving. Just a few things that helped me in the past.

James

are you using symetry or periodic boundary conditions?

How about the outlet pressure? It is not the atmosphere.

How do you know the total pressure at inlet?

Eric