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- - **SIMPLE loop in interTrackFoam**
(*https://www.cfd-online.com/Forums/openfoam-solving/57817-simple-loop-intertrackfoam.html*)

Hello,
I have a question cHello,
I have a question concerning the SIMPLE loop in interTrackFoam, especially about the velocity equation. In interTrackFoam, UEqn is implemented this way: tmp<fvvectormatrix> UEqn ( fvm::ddt(rho, U) + fvm::div(phiNet, U) - fvm::laplacian(mu, U) ); UEqn().relax(); solve(UEqn() == - fvc::grad(p)); whereas in other solvers using the SIMPLE algorithm, it is implemented this way: tmp<fvvectormatrix> UEqn ( fvm::ddt(U) +fvm::div(phi,U) -fvm::laplacian(nu,U) ); UEqn.relax(); solve (UEqn == -fvc::grad(p)); I understand that the difference is that the interTrackFoam equation is the second one multiplied by rho, but in that case, should the second term -fvc::grad(p) not be multiplied by rho as well? so that the equation should become something like: tmp<fvvectormatrix> UEqn ( fvm::ddt(rho, U) + fvm::div(phiNet, U) - fvm::laplacian(mu, U) ); UEqn().relax(); solve(UEqn() == - rho()*fvc::grad(p)); or something like that? If what I said is wrong, is there something that I misunderstood in the equation solving in OpenFOAM? Otherwise, how should I write the equivalent of the line solve(UEqn() == - rho()*fvc::grad(p)); ? Thank you in advance |

Hi Virginie
If you look at Hi Virginie
If you look at 0/p in the hydroFoil test case, then you will see that the pressure has dimensions which differ from those in for instance simpleFoam-tutorials. Thus rho is incorporated in p. I hope it did clarify you doubts. Best regards, Niels |

Thank you Niels.
Indeed, I had not pointed out that the p dimensions was different. Thank you for your answer, it helped a lot! Virginie |

Hi,
just a quick message to say that I resolved my problems. This high pressure is not a divergence, it is the real result. My problems come from the fact that the cells of my mesh become very flat. Virginie |

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