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Misleading low Residuals long before Steady state solution is reached!

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Old   August 20, 2013, 06:16
Default Misleading low Residuals long before Steady state solution is reached!
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Hello dear Foamers,
I am doing a turbulent incompressible steady state Simulation involving a porous media using porousSimpleFoam.
While my pressure Residuals drop below 1e-3 after about 1000 iterations and then oscillate slightly around 5e-4 , I have obviously not reached my steady state solution at this point as can be seen in Uplot.png where the velocities at 4 points on the surface of the porous media are plotted against the iterations. Judging by the residuals alone I would have stopped the simulations way to early. I am wondering what could cause this situation where the residuals are a very bad measure of convergence?
I set a low relaxation factor for the velocity following these guidelines:

The realizable kepsilon model was switched on after 300 iterations.
I attached my checkMeshlog my fvSolution and fvSchemes file.

I have to do a parameter study and if possible I would like to reduce the necessary number of iterations before starting with it.

Thanks for any help and thoughts on this.

Best wishes,
Attached Images
File Type: png Uplot.png (22.7 KB, 8 views)
Attached Files
File Type: txt fvSolution.txt (1.9 KB, 3 views)
File Type: txt fvSchemes.txt (2.5 KB, 0 views)
File Type: txt logM.txt (3.3 KB, 2 views)
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