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High drag coefficient Cd values

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Old   December 5, 2015, 22:49
Default High drag coefficient Cd values
Join Date: Sep 2015
Posts: 30
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czhongrong is on a distinguished road
I've run my simulations and I want to extract the Cd values for my cylinder.

1) I added the following function block in my controlDict (same template which I found online).
type forces;
functionObjectLibs (""); //Lib to load
patches (cylinder);
pName p;
UName U;
log true;
rhoName rhoInf;
rhoInf 1; //Reference density for fluid
CofR (0 0 0);
outputControl timeStep;
outputInterval 1;

type forceCoeffs;
functionObjectLibs ("");
outputControl timeStep;
outputInterval 1;
patches (cylinder);
pName p;
UName U;
log true;
rhoName rhoInf;
rhoInf 1;
CofR (0 0 0);
liftDir (0 1 0);
dragDir (1 0 0);
pitchAxis (0 1 0);
magUInf 1;//reference velocity
lRef 1;//reference length to calculate moment coefficient
Aref 1;//*****Modification is required when the mesh is changed.
2) I open the forceCoeffs.dat file and extract the long list of Cd values.

3) I took the average of all the values and I am getting Cd values in the range of 16-20.

May I know what is wrong? Or that shouldn't be the way I should be doing. Are there parameters I should change in the forceCoeffs block that are specific to the case that I am running? HELP!
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