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note about convergence

Posted March 26, 2013 at 05:39 by skeptik

Quote:
Originally Posted by chegdan View Post
Nick,

There are some strategies that I would try to get these residuals down to something you would like.
  1. Lower your pressure relTol by an order of magnitude compared to U i.e. relTol = 0.001 for P and relTol = 0.01 for U.
  2. Without knowing the mesh you are using you may need to increase the nonorthogonal corrector by 1 or 2. if you are using a tet mesh...then there are many things you can do.
  3. Use first order schemes to start with (you will move to higher order ones later)
  4. Obtain an initital velocity field with potentialFoam
  5. Using simpleFoam, the intial condition from potentialFoam, and first order schemes...turn turbulence OFF and once convergence seems to bottom out, turn turbulence on while the simulation is running
  6. Once a steady-state is obtained, stop the simulation, switch to second order schemes and restart the simulation with turbulence on and see if that helps

There are a lot of other strategies that you can try, but this one might be sufficient. Without knowing more details like divergence schemes; mesh structure and checkmesh results; y+ values; and boundary conditions there is not much to add on my part.

I would look at the thread SimpleFoam convergence problems and then move on to a search of the forum. There are many threads about simpleFoam convergence...but my list of threads is not in front of me right now. good luck.
pretty interesting
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