Flow around cylinder, forcing term
Hi everyone,
I am a new FOAM user and I am trying to model an oscillating (sinusoidal) flow around a free circular cylinder in 2D. I have some trouble, trying to add a forcing term to the UEqn. (I use a pimpleFoam solver). The UEqn looks like this: ================================================== ====== dimensionedVector forcing( "forcing", dimensionSet(0,1,-2,0,0,0,0), (Um1*omega*Foam::cos(omega*runTime.value()) + slope)*forceDir ); fvVectorMatrix UEqn ( fvm::ddt(U) + fvm::div(phi, U) + turbulence->divDevReff(U) - forcing ); if (ocorr != nOuterCorr-1) { UEqn.relax(); } if (momentumPredictor) { solve(UEqn == -fvc::grad(p)); // forcing is included in UEqn } ================================================== ====== It all runs fine with no errors, however the velcity accelerates. This means that if Um1 is eg. 0.2 m/s, then in the beginning Ux oscillates between (-0.2 ; 0.2). But after some time it increases/decreases to oscillate between eg. (0 ; 0.4), (0.2 ;0.6), (0.4 ; 0.8) etc. I'm thinking, that a pressure gradient is developing, but I don't know why.. I have zeroGradient conditions for both velocity and pressure at inlet+outlet. The top and bottom boundaries are both slip. Does anyone have an idea of, what I have done wrong? (I use OpenFoam 1.6-ext). Thanks in advance :) |
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