# flow around 2-Dimension cylinder

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 July 8, 2009, 09:53 flow around 2-Dimension cylinder #1 New Member   qqj Join Date: Jun 2009 Posts: 12 Rep Power: 8 Hi, I am calculating flow around 2-D cylinder at Re=200 with OpenFOAM. The radius of the cylinder is 0.5m. The velocity of incoming flow is 1m/s. Mu equals to 0.005. The full grid is shown here: grid I used the following schemes: ddtSchemes { default CrankNicholson 0.5; } gradSchemes { default Gauss linear; grad(p) Gauss linear; } divSchemes { default none; div(phi,U) Gauss linear; } laplacianSchemes { default none; laplacian(nu,U) Gauss linear corrected; laplacian(1|A(U),p) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(HbyA) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } The standard ICCG and BICCG solvers are used untill convergence to resectively 1e-6 and 1e-5 is obtained. The time step was chosen to be 0.01. Also the standard boundary conditions are applied: inlet: U fixed and zeroGradient for p outlet: p fixed and zeroGradient for U upper/lower boundary: zeroGradient for p and for U forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); patches (circle); //change to your patch name rhoInf 1; CofR (0 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 0); magUInf 1; lRef 1; Aref 1.0; } BrazaM (1985 N um )' result: time average of cd=1. 31; amplitude of cl=0. 65; st=0. 194. my result: time average of Cd is about 1.9, larger than 1.31; the amplitude of Cl is about 1.0 , more than 0.65; but the st number equals to 0.196 close to the result. Is someone having any ideas on what's wrong with it? Do I use the proper schemes? Are the bounday conditions correct? Thanks, Ranas

 July 9, 2009, 03:46 need your help, thanks #2 New Member   qqj Join Date: Jun 2009 Posts: 12 Rep Power: 8 I am calculating flow around 2-D cylinder at Re=200 with OpenFOAM. The radius of the cylinder is 0.5m. The velocity of incoming flow is 1m/s. Mu equals to 0.005. The full grid is shown here: grid I used the following schemes: ddtSchemes { default CrankNicholson 0.5; } gradSchemes { default Gauss linear; grad(p) Gauss linear; } divSchemes { default none; div(phi,U) Gauss linear; } laplacianSchemes { default none; laplacian(nu,U) Gauss linear corrected; laplacian(1|A(U),p) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(HbyA) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } The standard ICCG and BICCG solvers are used untill convergence to resectively 1e-6 and 1e-5 is obtained. The time step was chosen to be 0.01. Also the standard boundary conditions are applied: inlet: U fixed and zeroGradient for p outlet: p fixed and zeroGradient for U upper/lower boundary: zeroGradient for p and for U forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); patches (circle); //change to your patch name rhoInf 1; CofR (0 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 0); magUInf 1; lRef 1; Aref 1.0; } BrazaM (1985 N um )' result: time average of cd=1. 31; amplitude of cl=0. 65; st=0. 194. my result: time average of Cd is about 1.9, larger than 1.31; the amplitude of Cl is about 1.0 , more than 0.65; but the st number equals to 0.196 close to the result. Is someone having any ideas on what's wrong with it? Do I use the proper schemes? Are the bounday conditions correct? Thanks, Ranas

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