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 August 6, 2007, 12:20 Hi Hrvoje, Sorry to not rep #1 Member   Hoang-Lam Join Date: Mar 2009 Location: Lausanne, Switzerland Posts: 60 Rep Power: 9 Hi Hrvoje, Sorry to not replying you for the last time (about a_N coefficients. I re-read your thesys, but it stil not ok for me), but in emmergency, I want to know where I'm wrong in the implementation of a Stokes solver: I begin with the simpleFOam.C file: so I just removed the div(phi,U) and changed some "minus" by "plus", according to he discretisation of Navier-Stokes, explained in your thesys. (in my simulation, I put turbulence OFF) **************************** tmp UEqn (turbulence->divR(U)); UEqn().relax(); solve(UEqn() == -fvc::grad(p)); p.boundaryField().updateCoeffs(); volScalarField AU = UEqn().A(); U = UEqn().H()/AU; UEqn.clear(); phi = fvc::interpolate(U) & mesh.Sf(); adjustPhi(phi, U, p); for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++) { fvScalarMatrix pEqn ( // I put a "minus" here, because now: Up=[H(U)+grad(p)]/ap, so the discretisation of div(U)=0 gives me the equation of pressure below: fvm::laplacian(1.0/AU, p) == -fvc::div(phi)); pEqn.setReference(pRefCell, pRefValue); pEqn.solve(); if (nonOrth == nNonOrthCorr) { // "+=" instead of "-=" because F = S.Uf = S.[H(U)/ap]f + S.[grad(p)/ap]f phi += pEqn.flux(); } } # include "continuityErrs.H" p.relax(); // "+=" instead of "-=" because Up=[H(U)+grad(p)]/ap U += fvc::grad(p)/AU; U.correctBoundaryConditions(); } ******************** the end of the program is the same. It seems so easy, but I can't get by myself. I just need your patience to tell me where I'm wrong. Thanks in advance, Lam

 August 7, 2007, 12:15 just take a little look please #2 Member   Hoang-Lam Join Date: Mar 2009 Location: Lausanne, Switzerland Posts: 60 Rep Power: 9 just take a little look please

 August 7, 2007, 13:06 ? You have messed up the signs #3 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,783 Rep Power: 22 ? You have messed up the signs: just delete the convection terms and use a symmetric solver for the momentum equation. I haven't got time to go through this in detail, but it should really be as simple as that. Hrv __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 August 8, 2007, 03:56 Hi Hrvoje, Thanks to reply #4 Member   Hoang-Lam Join Date: Mar 2009 Location: Lausanne, Switzerland Posts: 60 Rep Power: 9 Hi Hrvoje, Thanks to reply me. Ok, I'm going to delete the convection term... even if I don't understand why the signs are wrong. Hope that you will explain me when you get more time. Cheers, Lam

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