Confused about pEqn

xianqiejiao · December 26, 2014, 02:29

Hi everyone,

I am currently doing some work on the caveatingFoam. In which the pEqn is as following:

Code:

fvScalarMatrix pEqn
        (
            fvm::ddt(psi, p)
          - (rhol0 + (psil - psiv)*pSat)*fvc::ddt(alphav) - pSat*fvc::ddt(psi)
          + fvc::div(phiv, rho)
          + fvc::div(phiGradp)
          - fvm::laplacian(rhorAUf, p)
        );

According to the literature （Phd thesis by Fabian), the pEqn should be

Code:

fvm::ddt(psi, p)
          - (rhol0 + (psil - psiv)*pSat)*fvc::ddt(alphav) - pSat*fvc::ddt(psi)
          + fvc::div(phiv, rho)

is you write every term one by one.
so what is the last two terms mean? :

Code:

+ fvc::div(phiGradp)
          - fvm::laplacian(rhorAUf, p)

And I am also confused about the last step in pimple loop:

Code:

if (pimple.finalNonOrthogonalIter())
        {
            phiv += (phiGradp + pEqn.flux())/rhof;
        }

Can anyone give me some hint here? If they are for numerical reasons, where can I find information for them? I didn't see much about this in CFD books I have read. I assume they are very important as I can find the similar term in many other solvers.

Kind regards and Merry Christmas!

mg.mithun · February 29, 2016, 08:36

Hi xianqiejiao,
I hope you would have found answers for this question by now. If so can you please share it in the forum so that it will be useful for people like me who are struggling with similar problems. I appreciate your response

MG

December 26, 2014, 02:29	Confused about pEqn	#1
xianqiejiao New Member BO Join Date: Dec 2014 Posts: 21 Rep Power: 11	Hi everyone, I am currently doing some work on the caveatingFoam. In which the pEqn is as following: Code: fvScalarMatrix pEqn ( fvm::ddt(psi, p) - (rhol0 + (psil - psiv)pSat)fvc::ddt(alphav) - pSatfvc::ddt(psi) + fvc::div(phiv, rho) + fvc::div(phiGradp) - fvm::laplacian(rhorAUf, p) ); According to the literature （Phd thesis by Fabian), the pEqn should be Code: fvm::ddt(psi, p) - (rhol0 + (psil - psiv)pSat)fvc::ddt(alphav) - pSatfvc::ddt(psi) + fvc::div(phiv, rho) is you write every term one by one. so what is the last two terms mean? : Code: + fvc::div(phiGradp) - fvm::laplacian(rhorAUf, p) And I am also confused about the last step in pimple loop: Code: if (pimple.finalNonOrthogonalIter()) { phiv += (phiGradp + pEqn.flux())/rhof; } Can anyone give me some hint here? If they are for numerical reasons, where can I find information for them? I didn't see much about this in CFD books I have read. I assume they are very important as I can find the similar term in many other solvers. Kind regards and Merry Christmas! Last edited by xianqiejiao; December 26, 2014 at 07:40.

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February 29, 2016, 08:36		#2
mg.mithun New Member Myth Join Date: Jul 2011 Location: Unitek kingdom Posts: 17 Rep Power: 14	Hi xianqiejiao, I hope you would have found answers for this question by now. If so can you please share it in the forum so that it will be useful for people like me who are struggling with similar problems. I appreciate your response MG