CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   FLOW-3D (https://www.cfd-online.com/Forums/flow-3d/)
-   -   pressure iterations not converging (https://www.cfd-online.com/Forums/flow-3d/105819-pressure-iterations-not-converging.html)

VikramR August 9, 2012 12:54

pressure iterations not converging
 
Hello everyone, I am trying to model a reactor and I am having a few difficulties in doing so. The pressure iterations are not converging ( I tried setting max iterations to 5000, GMRES etc).
Are there any strategies to make it converge?
Please help.

Thanks in advance,
Vikram

dmilano August 13, 2012 18:10

Well, there are a lot of things that you can try... Check the troubleshooting section of the manual for suggestions. My recommendations:

1. Check that the initial and boundary conditions are reasonable and match reality.
2. Check any STL files for problems
3. Check your mesh. Cell aspect ratios should be less than ~3:1; ideally closer to 1:1. The cell size should not change by more than a factor of two between multi-block meshes and the grid lines should align.
4. Check that epsi/epsadj are reasonable
5. Try adding some fluid compressibility (rcsql/rcsqv)
6. Reduce the time step size
7. Increase GMRES subspace size (mrstrt)
8. Try SOR with omega<1 and itmax ~5000

As a side note, using itmax=5000 with GMRES usually doesn't work well. If the problem doesn't converge with the default settings it is usually an indicator of some other problem.

VikramR August 13, 2012 18:13

Thank you very.
I figured it out, the problem was with my initial conditions.
Thanks again Mr. dmilano


All times are GMT -4. The time now is 12:45.