# Question about the packingLimter.H and alpha.H in twoPhaseEulerFoam

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 November 21, 2011, 11:05 Question about the packingLimter.H and alpha.H in twoPhaseEulerFoam #1 Member   Charlie Join Date: Dec 2010 Location: 415 Kinross Dr. Newark, DE 19711 Posts: 78 Rep Power: 6 Hi All, I'm running a twoPhaseEulerFoam case using 1DV ( just 1 grid in x and z direction, but in y direction I'm using 200 grids) and find something interesting: The mass of particle phase is not conserved basically. After Initialization, the volume averaged fraction is 0.198, after 400s' running, the volume averaged fraction becomes about 0.244, apparently, the mass of dispersed phase is not conserved. In the above case, I'm using OF-1.7.1, I've turned on the PackingLimter, and the alphaEx=0.62, I've set g0=0, and turned the kinetic theory on. I guess my question is what do you think the problem is? Could somebody explain something about the packingLimiter? Thanks a lot! Zhen

November 27, 2011, 19:12
#2
Member

Kai
Join Date: May 2010
Location: Stockholm
Posts: 40
Rep Power: 7
Quote:
 Originally Posted by cheng1988sjtu Hi All, I'm running a twoPhaseEulerFoam case using 1DV ( just 1 grid in x and z direction, but in y direction I'm using 200 grids) and find something interesting: The mass of particle phase is not conserved basically. After Initialization, the volume averaged fraction is 0.198, after 400s' running, the volume averaged fraction becomes about 0.244, apparently, the mass of dispersed phase is not conserved.
Of course the void fraction is not conserved unless it goes into steady state.

Quote:
 Originally Posted by cheng1988sjtu In the above case, I'm using OF-1.7.1, I've turned on the PackingLimter, and the alphaEx=0.62, I've set g0=0, and turned the kinetic theory on. I guess my question is what do you think the problem is? Could somebody explain something about the packingLimiter?
Physically, the PackingLimter means nothing and we should not have PackingLimter. The value alpha should only updated by its transport eqn. Technically, since there might exist a serious problem when alpha goes too high, we may want to keep alpha roughly below a value (but cannot promise alpha<alphaMax strictly). Future model together with mass transport eqn should be developed in order to keep/promise a reasonable alpha.
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Kai

November 28, 2011, 17:17
#3
Member

Charlie
Join Date: Dec 2010
Location: 415 Kinross Dr. Newark, DE 19711
Posts: 78
Rep Power: 6
Thanks, at first I thought it was due to the artificial redistribution of alpha in packingLimiter.H, however, investigation of the code just proved me wrong, there is no problem with the packingLimiter.H

Maybe that's because I'm just using 1 grid in x and z direction. since when I change it to 2D, there seems to be no such problem.

Zhen

Quote:
 Originally Posted by kaifu Of course the void fraction is not conserved unless it goes into steady state. Physically, the PackingLimter means nothing and we should not have PackingLimter. The value alpha should only updated by its transport eqn. Technically, since there might exist a serious problem when alpha goes too high, we may want to keep alpha roughly below a value (but cannot promise alpha

 Tags alphaeqn, packinglimiter, twophaseeulerfoam

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