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July 21, 2016, 08:11 |
Handling of drag in multiphase flow solvers
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#1 |
Senior Member
Dr. Fabian Schlegel
Join Date: Apr 2009
Location: Dresden, Germany
Posts: 222
Rep Power: 18 |
Dear Foamers,
hopefully, one can help me on a more ore less simple question: Why is the explicit part of the drag in twophaseEulerFoam, multiphaseEulerFoam, reactingMultiphaseEulerFoam and as well in the old bubbleFoam added to the pressure equation, in particular added to phiHbyA and HbyH? Code:
phiHbyAs[phasei] += fvc::interpolate(rAUs[phasei]*K)*MRF.absolute(phase2->phi()); HbyAs[phasei] += rAUs[phasei]*K*phase2->U(); Code:
forAllConstIter(phasePair, pair, iter) { const volVectorField& U = phase->U(); *eqns[phase->name()] -= fvm::Sp(K, U); Swap(phase, otherPhase); } Code:
K*otherphase->U() Best regards Fabian |
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February 16, 2017, 12:49 |
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#2 |
New Member
AHaley
Join Date: May 2015
Posts: 2
Rep Power: 0 |
Maybe you've already figured this out, but I think I know what the deal is there.
Since K is a sum of the drag coeffs between all the other phases and that phase, you can only include the implicit part there (ie. for phase 1 (Kd12+Kd13+Kd14)*U1). The individual explicit drag terms between each phase pair have to be calculated separately (ie. Kd12*U2+Kd13*U3+Kd14*U4 etc.), which should be done in the Peqn. |
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February 20, 2017, 06:46 |
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#3 |
Senior Member
Dr. Fabian Schlegel
Join Date: Apr 2009
Location: Dresden, Germany
Posts: 222
Rep Power: 18 |
I wouldn't agree with that. The pair includes all information about the other phase, so you can add Kd12*U2 piece by piece with a loop over the drag model table. I guess the reason is that one do not want to interpolate the explicit drag within the A matrix. One want to interpolate the drag separately, like the pressure in RhieChow algorithm.
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February 20, 2017, 06:58 |
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#4 |
New Member
AHaley
Join Date: May 2015
Posts: 2
Rep Power: 0 |
Yes it is set up so that you could calculate the explicit drag terms there, but that would be incorrect. The explicit part of the drag must be included in H, and therefore pEqn, as it is not a multiplier of the phase velocity in that cell or in any of the neighbours. The colocated grid is not the issue, in this case.
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February 20, 2017, 07:56 |
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#5 |
Senior Member
Dr. Fabian Schlegel
Join Date: Apr 2009
Location: Dresden, Germany
Posts: 222
Rep Power: 18 |
Ok, you are right, this was my mistake. The explicit part of the drag is added to H and not to A.
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