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Nico A. July 5, 2011 12:21

Drag coefficient for a sphere
 
Hello to all,

I am doing simulations on a sphere at high Re ( 1*e5 - 1*e7 ) using the k-omega-SST turbulence model. Unfortunatly I got the same drag coefficient (Cd) for the different Re and also flow behavior looks the same.
Code:

FoamFile
{
    version    2.0;
    format      ascii;
    class      dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application    simpleFoam;

startFrom      startTime;

startTime      0;

stopAt          endTime;

endTime        1200;

deltaT          1;

writeControl    timeStep;

writeInterval  50;

purgeWrite      0;

writeFormat    ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision  6;

runTimeModifiable yes;

functions
{
        forces
        {
                type forces;
                functionObjectLibs ( "libforces.so" );               
                outputControl timeStep;
                outputInterval 1;
                patches
                (
                sphere                                       
                );
                                                               
                rhoName rhoInf;
                log true;                                       
                rhoInf 1.2041;
                CofR ( 0 0 0 );
        }
        forcesCoeffs
        {
                type forceCoeffs;
                functionObjectLibs ( "libforces.so" );               
                outputControl timeStep;
                outputInterval 1;
                patches
                (
                sphere                                       
                );
                                                               
                rhoName rhoInf;
                log true;                                       
                rhoInf 1.2041;
                CofR ( 0 0 0 );
                liftDir ( 0 1 0 );
                dragDir ( 1 0 0 );
                pitchAxis ( 0 0 0 );
                magUInf 15;
                lRef 0.4;
                Aref 0.125662;
        }
}

I allways adjusted the values for k and omega the different velocities at the inlet (and also at the sphere/wall). I am not sure which values can be changed and which must not be changed. Does anyone have some advices?

Best regards Nico


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