# Hi,I have a question about momentum equation in interFoam

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 January 11, 2013, 10:19 Hi,I have a question about momentum equation in interFoam #1 New Member   anonymous Join Date: Apr 2010 Posts: 14 Rep Power: 7 Dear Foamers: I have read Henrik Rusche's phd thesis.Now i meet a question in the momentum equation of interFoam. Mr. Rusche defined an 'H' operator AH=As-An*phi where 'As' means source vector.Does As include the item like -grad(p)-g*x*grad(rho)...?Or What included in As?Thank you very much！

 January 13, 2013, 06:59 #2 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 173 Rep Power: 8 Take a look at the interFoam/UEqn.H: Code: ``` fvVectorMatrix UEqn ( fvm::ddt(rho, U) + fvm::div(rhoPhi, U) + turbulence->divDevRhoReff(rho, U) == sources(rho, U) );``` In the case of UEqn.H(), 'H' operator is constructed from the above fvVectorMatrix UEqn. In the above definition of UEqn, there is no terms corresponding to grad(p) and g*x*grad(rho), so these terms are not included in the H operator in the interFoam solver. Fumiya

 January 14, 2013, 08:47 #3 New Member   anonymous Join Date: Apr 2010 Posts: 14 Rep Power: 7 Here's the UEqn.H in of 2.1.1 surfaceScalarField muEff ( "muEff", twoPhaseProperties.muf() + fvc::interpolate(rho*turbulence->nut()) ); fvVectorMatrix UEqn ( fvm::ddt(rho, U) + fvm::div(rhoPhi, U) - fvm::laplacian(muEff, U) - (fvc::grad(U) & fvc::grad(muEff)) //- fvc::div(muEff*(fvc::interpolate(dev(fvc::grad(U)) ) & mesh.Sf())) ); UEqn.relax(); if (pimple.momentumPredictor()) { solve ( UEqn == fvc::reconstruct ( ( fvc::interpolate(interface.sigmaK())*fvc::snGrad(a lpha1) - ghf*fvc::snGrad(rho) - fvc::snGrad(p_rgh) ) * mesh.magSf() ) ); } The H operator is constructed by : fvVectorMatrix UEqn ( fvm::ddt(rho, U) + fvm::div(rhoPhi, U) - fvm::laplacian(muEff, U) - (fvc::grad(U) & fvc::grad(muEff)) //- fvc::div(muEff*(fvc::interpolate(dev(fvc::grad(U)) ) & mesh.Sf())) ); Right?

 January 15, 2013, 08:26 #4 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 173 Rep Power: 8 I think so. Fumiya shchao likes this.

 January 28, 2013, 22:27 #5 Senior Member     Santiago Marquez Damian Join Date: Aug 2009 Location: Santa Fe, Santa Fe, Argentina Posts: 420 Rep Power: 15 Hi, the H operator gives which is defined in Hrv thesis for the implicit terms used in the fvVectorMatrix declaration. Regards. __________________ Santiago MÁRQUEZ DAMIÁN, Ph.D. Post-doctoral Fellow Research Center for Computational Mechanics (CIMEC) - CONICET/FICH-UNL T.E.: 54-342-4511594 Ext. 1005 Güemes 3450 - (3000) Santa Fe Santa Fe - Argentina http://www.cimec.org.ar

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