Blowing up epsilon using wall BC interfoam

josee · May 12, 2017, 18:14

Hello FOAM users

Currently I'm facing some difficulties in the solution of a simple case of a 3d rectangular duct spillway simulation. I am using interFoam with an initial volume of fluid after running the setFields utility. I have run the case with the following BC:

The results are OK when defining the side walls as symmetry but if I turn them into a wall BC, the bounds for epsilon after 1/3 of the simulation time (30s) blows up and the automatic adjusted timestep get as low as 1e-34. I have done a bigger model in the Y direction and also I have done a more refined mesh, in order to see if the thin model is the cause of the problem, but I'm still having the same error in the execution when changing the symmetry BC to wall BC. Does anybody have any idea of this behavior?

Thanks in advance

piu58 · May 13, 2017, 02:04

If your image shows the actual geometry: You have only 2 cells in spanwise direction. Every cell has to fulfill a b.c. then. I recommend to use more cells, at least 6, better 8.

josee · May 14, 2017, 21:47

Thank you for your response Mr. Pilz
I have run other geometries longer in the spanwise direction and also with dense meshes, about 100 divisions in the spanwise direction, and I keep having trouble in the solution. Epsilon keeps blowing up and the timestep getting small on each iteration.

piu58 · May 15, 2017, 01:39

May you provide an example, for I may look at the case by myself? Of course I prefer a simple one, which shows the effect.

May 13, 2017, 02:04		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	If your image shows the actual geometry: You have only 2 cells in spanwise direction. Every cell has to fulfill a b.c. then. I recommend to use more cells, at least 6, better 8. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

May 15, 2017, 01:39		#4
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	May you provide an example, for I may look at the case by myself? Of course I prefer a simple one, which shows the effect. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

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May 14, 2017, 21:47		#3
josee New Member Jose Join Date: May 2009 Location: Tokyo Posts: 4 Rep Power: 17	Thank you for your response Mr. Pilz I have run other geometries longer in the spanwise direction and also with dense meshes, about 100 divisions in the spanwise direction, and I keep having trouble in the solution. Epsilon keeps blowing up and the timestep getting small on each iteration.