MRFInterFoam: Trouble with direction of gravity / Continuity error cannot be removed

bengt · May 28, 2010, 12:15

Dear Foamers,

I've modified the mixerVessel2D in order to simulate a rotating shaft (cylinder) within a circular housing using MRFInterFoam. The housing is filled with oil up to the centre (fluid fraction 50%), and, accordingly, gravity is set to the -y direction.
The problem I'm facing now is that I can't get the solver running due to the following error: FOAM FATAL ERROR: Continuity error cannot be removed by adjusting the outflow.
Without gravity or with gravity acting in -z-direction (parallel to the rotational axis), there is no problem. Boundary conditions are set according to the tutorial case. Changing the pressure bc to buoyantPressure doesn't have any effect.

What am I doing wrong???

Any ideas or help are greatly appreciated!!
Kind regards, have a nice weekend
Bengt

nimasam · May 28, 2010, 15:23

hi friend
i suggest change mesh size or time step , some times its helpful.

bengt · May 28, 2010, 15:45

Hi nima,

thanks a lot for your reply!! Indeed, reducing the timestep/maxCo gets the solver working with the fluid fraction remaining constant - however, after 2 seconds it crashes giving the same error message...do you have any recommendations regarding the boundary conditions and discretization schemes / solver controls for such a case?

Kind regards
bengt

May 28, 2010, 12:15	MRFInterFoam: Trouble with direction of gravity / Continuity error cannot be removed	#1
bengt New Member Join Date: Mar 2009 Location: Germany Posts: 4 Rep Power: 17	Dear Foamers, I've modified the mixerVessel2D in order to simulate a rotating shaft (cylinder) within a circular housing using MRFInterFoam. The housing is filled with oil up to the centre (fluid fraction 50%), and, accordingly, gravity is set to the -y direction. The problem I'm facing now is that I can't get the solver running due to the following error: FOAM FATAL ERROR: Continuity error cannot be removed by adjusting the outflow. Without gravity or with gravity acting in -z-direction (parallel to the rotational axis), there is no problem. Boundary conditions are set according to the tutorial case. Changing the pressure bc to buoyantPressure doesn't have any effect. What am I doing wrong??? Any ideas or help are greatly appreciated!! Kind regards, have a nice weekend Bengt

May 28, 2010, 15:45	problem persists	#3
bengt New Member Join Date: Mar 2009 Location: Germany Posts: 4 Rep Power: 17	Hi nima, thanks a lot for your reply!! Indeed, reducing the timestep/maxCo gets the solver working with the fluid fraction remaining constant - however, after 2 seconds it crashes giving the same error message...do you have any recommendations regarding the boundary conditions and discretization schemes / solver controls for such a case? Kind regards bengt

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May 28, 2010, 15:23		#2
nimasam Senior Member Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,267 Blog Entries: 1 Rep Power: 25	hi friend i suggest change mesh size or time step , some times its helpful.