[Roland R]

Hello,

I make a simulation to a steady state compressible flow. The pressure ratio is 10. I defined the inlet/outlet boundary conditions with pressure values. There is a valve in the flow field, the force at the valve is the most important output of the simulation.

In the first simulation the next settings were defined in Solver Control:

- Advection scheme: High resolution
- Length scale option: Conservative
- Time scale factor: 1

With these settings the force at the valve has not converged, it has flucuated between 18 and 20N. I tried to help the convergence by the next settings

- Advection scheme: Upwind
- Length scale option: Aggressive
- Time scale factor: 5

The simulation has converged, the force at the valve was constant 12N.

Finally I tried to go back to the original Solver Control settings. Naturally this definition file was initalized from the previous converged result. I thought that the convergence will be OK in this case, but unfortunately not. The force at the valve turned back between 18 and 20N and it has not converged...

What can be the reason of this problem?

Thanks
Roland

[ghorrocks]

http://www.cfd-online.com/Wiki/Ansys...gence_criteria