# pEqn and mixture density in cavitatingFoam and cavitatingDyMFoam

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 March 20, 2020, 06:49 pEqn and mixture density in cavitatingFoam and cavitatingDyMFoam #1 New Member   peyman havaej Join Date: Jan 2016 Posts: 8 Rep Power: 6 Dear All I use the cavitating flow solver in the OpenFOAM. The cavitatingFoam solver employes a Homogeneous Equilibrium Model (HEM), in which the pressure equation depends on the compressibility of each phase and the density of the mixture is calculated according to an equilibrium barotropic equation. In the OpenFOAM v-6, there are minor differences in the pressure and density equation between cavitatingFoam and cavitatingDyMFoam (mesh motion). For example, in pEqn: cavitatingFoam: Code: ```fvScalarMatrix pEqn ( fvm::ddt(psi, p) - (rhol0 + (psil - psiv)*pSat)*fvc::ddt(alphav) - pSat*fvc::ddt(psi) + fvc::div(phi, rho) + fvc::div(phiGradp) - fvm::laplacian(rhorAUf, p) );``` cavitatingDyMFoam: Code: ```fvScalarMatrix pEqn ( fvc::ddt(rho) + psi*correction(fvm::ddt(p)) + fvc::div(phi, rho) + fvc::div(phiGradp) - fvm::laplacian(rhorAUf, p) );``` for the density of mixture: cavitatingFoam: Code: ``` rho == max ( psi*p + alphal*rhol0 + ((alphav*psiv + alphal*psil) - psi)*pSat, rhoMin );``` cavitatingDyMFoam: Code: ``` volScalarField rho0(rho - psi*p); ... ... ... rho == max(rho0 + psi*p, rhoMin);``` While I can understand the implementation of both solvers, I think pEqn and density correction in the static and Dynamic mesh solvers are not the same. For clarification, Code: `psi*correction(fvm::ddt(p))` is not equal to the Code: ` fvm::ddt(psi, p)` Moreover, the density correction obviously is not the same. Please correct me if I am wrong. Do you know what is the main reason behind this difference in the implementation of cavitatingFoam and cavitatingDyMFoam? Thanks. Whit Kind Regards, Peyman