[rdbisme]

Hello,

I'm working with reactingTwoPhaseEulerFoam for the simulation of slush flows (i.e. slurry flows in which the solid particulate is the same fluid as the carrier but solidified) and I would like to investigate the possibility of allowing melting phase change between the two phases.

I looked quite a bit into ThermalPhaseChangePhaseSystem and InterPhaseCompositionPhaseSystem but they require to have a phaseModel that returns mass fraction equations (returned by the multiComponentPhaseModel) and in particular the way they handle mass transfer doesn't translate into a change in the volumetric phase fraction (there is no source term in the phase fraction equations for what I understand).

The model I'd like to implement is:



where the mass source term is retrieved from the latent heat


And then there are source terms in the energy equation and momentum equation accordingly.

Do you have any hints or suggestions?

In particular do you know someone or some material I could look for this? Moreover do you have any reference for the ThermalPhaseChangePhaseSystem and InterphaseCompositionPhaseSystem code?

[rdbisme]

As reference, for what concerns the volume fraction source term, there's a clarifying explanation from the developers:

https://bugs.openfoam.org/view.php?id=1881

[openfoammaofnepo]

Dear Ruben,

Based on the link you gave, the source or sink term for the volume fraction is included into the tdgdt in fluid.solve() function. Did you find the relation between dmdt and divU as mentioned in that bug report?

Thanks.

[rdbisme]

Originally Posted by openfoammaofnepo

Dear Ruben,

Based on the link you gave, the source or sink term for the volume fraction is included into the tdgdt in fluid.solve() function. Did you find the relation between dmdt and divU as mentioned in that bug report?

Thanks.

Hi, yes. The divU term is created in the pressure equation pEqn.H (OpenFOAM 4.x)

// Set the phase dilatation rates
            if (phase1.compressible())
            {
                phase1.divU(-pEqnComp1 & p_rgh);
            }
            if (phase2.compressible())
            {
                phase2.divU(-pEqnComp2 & p_rgh);
            }

where the terms pEqnComp1/2 are always created in the same file for pressure equation

if (fluid.transfersMass())
    {
        if (pEqnComp1.valid())
        {
            pEqnComp1.ref() -= fluid.dmdt()/rho1;
        }
        else
        {
            pEqnComp1 = fvm::Su(-fluid.dmdt()/rho1, p_rgh);
        }

        if (pEqnComp2.valid())
        {
            pEqnComp2.ref() += fluid.dmdt()/rho2;
        }
        else
        {
            pEqnComp2 = fvm::Su(fluid.dmdt()/rho2, p_rgh);
        }
    }

Is this what you ask?

Moreover I would really like if someone has some reference that talks about this dilatation term. I cannot understand where it comes from, my compressible background is not incredible, I would like to read a bit about it.

[openfoammaofnepo]

Dear Ruben,

Thank you - This makes sense.

Recently I am using this solver and reading some of its source files. I think we can discuss when necessary.

Thank you so much!

[rdbisme]

Originally Posted by openfoammaofnepo

Dear Ruben,

Thank you - This makes sense.

Recently I am using this solver and reading some of its source files. I think we can discuss when necessary.

Thank you so much!

I already implemented a mockup code for the melting, it compiles but surely is gonna have some flaws. Did not have time to test it. As I'll have time I'll post it so we can work on it and the community can make comments to help. Feel free to comment if you need something.

[openfoammaofnepo]

Do you mean you have already implemented a mass transfer model (or also heat transfer model) for melting under /PhaseSystems?

[rdbisme]

Originally Posted by openfoammaofnepo

Do you mean you have already implemented a mass transfer model (or also heat transfer model) for melting under /PhaseSystems?

Yes, I created a MeltingPhaseSystem that provides the dmdt term computed as I wrote in the first post. It inherits from HeatAndMassTransferPhaseSystem that already handles the source terms in momentum. I took inspiration from the ThermalPhaseChangePhaseSystem and the InterphaseCompositionPhaseSystem.

I don't know by the way if that is the correct way to go. . And still untested, so maybe it's just bulls***.

[openfoammaofnepo]

Dear Ruben,

Thank you so much. I am working on implementing a pyrolysis model for the phase change. Is it possible for you to post that file so that I can make a reference for my implementation? Thanks!

[rdbisme]

Originally Posted by openfoammaofnepo

Dear Ruben,

Thank you so much. I am working on implementing a pyrolysis model for the phase change. Is it possible for you to post that file so that I can make a reference for my implementation? Thanks!

Did you check first the two other phase change PhaseSystems? I'm no expert about Pyrolisys, but I imagine you're working with multicomponent or reacting phases. If that is the case, the other two models would be a better starting point than mine.

I'll by the way post it as soon as I have something, at least, running...

[openfoammaofnepo]

OK, thank you so much for the suggestions!

[openfoammaofnepo]

Dear Ruben,

Thank you for your explanation. When solving the alpha equation, the source term is included into dgdt, as mentioned in the link you provided. So dgdt is related to divU(). Also, the dilatation rate divU() is updated in pEqn.H, which is computed from pEqnComp. pEqnComp includes the mass addition or loss effects. Is this line of reasoning right?

Thanks!

[rdbisme]

Originally Posted by openfoammaofnepo

Dear Ruben,

Thank you for your explanation. When solving the alpha equation, the source term is included into dgdt, as mentioned in the link you provided. So dgdt is related to divU(). Also, the dilatation rate divU() is updated in pEqn.H, which is computed from pEqnComp. pEqnComp includes the mass addition or loss effects. Is this line of reasoning right?

Thanks!

From my understanding, I would say yes.

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