Maybe a bug in twoLiquidMixingFoam?

sharonyue · March 6, 2016, 03:40

Hi guys,

In twoLiquidMixingFoam, at first we solve alpha by MULES, then rhoPhi is calculated by the following:

Code:

rhoPhi = alphaPhi*(rho1 - rho2) + phi*rho2;

This makes sense. Then alpha is solved in alphaDissEqn.H, rhoPhi is updated as following:

Code:

rhoPhi += alpha1Eqn.flux()*(rho1 - rho2);

If we put them together, finally, rhoPhi will be:

rhoPhi = (alphaPhi + alpha1Eqn.flux())*(rho1 - rho2) + phi*rho2;

I think we need to delete the old alphaPhi in the code above, so in the alphaDissEqn.H, it should be:

Code:

rhoPhi = alpha1Eqn.flux()*(rho1 - rho2) + phi*rho2;

Am I right?

kaaja · March 29, 2018, 09:36

Did you solve this?

I am a little bit confused about the whole solver.
Rho works differently in the inertia term in Ueqn compared to the other terms, since it is rhoPhi*U that is used instead of alpha*rho*u*u.

Maybe the plus you mention is there because one wants both contribution from diffusion (alphaDiffusion) and the contribution from convection (standard VOF I believe)?

March 6, 2016, 03:40	Maybe a bug in twoLiquidMixingFoam?	#1
sharonyue Senior Member Dongyue Li Join Date: Jun 2012 Location: Beijing, China Posts: 838 Rep Power: 17	Hi guys, In twoLiquidMixingFoam, at first we solve alpha by MULES, then rhoPhi is calculated by the following: Code: rhoPhi = alphaPhi(rho1 - rho2) + phirho2; This makes sense. Then alpha is solved in alphaDissEqn.H, rhoPhi is updated as following: Code: rhoPhi += alpha1Eqn.flux()(rho1 - rho2); If we put them together, finally, rhoPhi will be: rhoPhi = (alphaPhi + alpha1Eqn.flux())(rho1 - rho2) + phirho2; I think we need to delete the old alphaPhi in the code above, so in the alphaDissEqn.H, it should be: Code: rhoPhi = alpha1Eqn.flux()(rho1 - rho2) + phi*rho2; Am I right? __________________ My OpenFOAM algorithm website: http://dyfluid.com By far the largest Chinese CFD-based forum: http://www.cfd-china.com/category/6/openfoam We provide lots of clusters to Chinese customers, and we are considering to do business overseas: http://dyfluid.com/DMCmodel.html

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March 29, 2018, 09:36		#2
kaaja Member Join Date: Apr 2017 Posts: 68 Rep Power: 9	Did you solve this? I am a little bit confused about the whole solver. Rho works differently in the inertia term in Ueqn compared to the other terms, since it is rhoPhiU that is used instead of alpharhouu. Maybe the plus you mention is there because one wants both contribution from diffusion (alphaDiffusion) and the contribution from convection (standard VOF I believe)?