# A question about UEqn.H in smallpoolfire2D

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 August 14, 2013, 01:12 A question about UEqn.H in smallpoolfire2D #1 Member   赵庆良 Join Date: Aug 2013 Posts: 56 Rep Power: 6 Hi Foamers: According to the following codes in UEqn.H: fvVectorMatrix UEqn ( fvm::ddt(rho, U) + fvm::div(phi, U) + turbulence->divDevRhoReff(U) == parcels.SU(U) ); UEqn.relax(); if (pimple.momentumPredictor()) { solve ( UEqn == fvc::reconstruct ( ( - ghf*fvc::snGrad(rho) - fvc::snGrad(p_rgh) )*mesh.magSf() ) ); } The momentum equation that the smallpoolFire2D sloves is fvm::ddt(rho, U)+ fvm::div(phi, U)+ turbulence->divDevRhoReff(U) ==parcels.SU(U)+fvc::reconstruct((- ghf*fvc::snGrad(rho)- fvc::snGrad(p_rgh))*mesh.magSf()). I understand all term in the equation except the term of "parcels.SU(U)". In many example in OF,there is no term of "parcels.SU(U)" in UEqn.H.How can understand the term?Is there any theory about the term? please some foamers know tell me.I really need help! Thank you!

 August 14, 2013, 14:33 #2 Senior Member     Matvey Kraposhin Join Date: Mar 2009 Location: Moscow, Russian Federation Posts: 330 Rep Power: 12 I'm not an expert in the fire simulation, but from the source which you provided (fireFoam) i understand that term parcels.SU(U) is an explicit contribution to the moment conservation of the fluid from parcels. This parcels (i guess!!!) are moving in the main fluid and term parcels.SU(U) used to include their drag and other forces. To obtain more information, you have to make a more deep look at the fireFoam solver source code

 August 15, 2013, 22:16 #3 Member   赵庆良 Join Date: Aug 2013 Posts: 56 Rep Power: 6 Thank you for your reply,now I make a more deep look at the fireFoam solver first!

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