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getting wrong forces and force coefficients in openfoam |
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January 21, 2019, 07:08 |
getting wrong forces and force coefficients in openfoam
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#1 |
Member
madz
Join Date: Sep 2018
Posts: 34
Rep Power: 7 |
hello everyone,
I'm running a 2D compressible naca0012 airfoil simulation at velocity 165m/s using rhoSimpleFoam solver. The simulation ran fine and i got accurate pressure and velocity contours as well as able to plot Cp vs x/c using paraview. But the values of the coefficients are way off than the standard results. Cl values are coming in the range of e-24 and same goes for the forces. To calculate forces and force coefficients i used the following code in the controlDict: function ( forces { type forces; // use the forces class functionObjectLibs ("libforces.so"); // "plugin" library to load patches (aerofoil_wall); // Name of patches to integrate forces //outputControl outputTime; // When to write the output rhoName rhoInf; // Name of the reference density rhoInf 0.000518; // Reference density for fluid CofR (0.33333 0 0); // Origin for moment calculations outputControl timeStep; outputInterval 1; } forceCoeffs_object { type forceCoeffs; // compute force-coefficients functionObjectLibs ("libforces.so"); patches (aerofoil_wall); //outputControl outputTime; rhoName rhoInf; rhoInf 0.000518; log true; CofR (0.33333 0 0); liftDir (0 1 0); // lift direction (parallel to U_inf) dragDir (1 0 0); // drag direction (normal to U_inf) pitchAxis (0 0 1); // rotational moment axis magUInf 165; // magnitude of U_inf (for normalization) lRef 1.0; // reference length Aref 1.0; // reference area outputControl timeStep; outputInterval 1; } ); I have attached the force and force coefficient. forceCoeffs.txt forces.txt Can someone please tell me the reason for error or what am i doing wrong. Thank you |
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January 22, 2019, 08:26 |
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#2 |
Senior Member
Zander Meiring
Join Date: Jul 2018
Posts: 125
Rep Power: 7 |
What fluid are you using to have such a low (5e-5) density value? air is around 1.2, which is what I assume you are simulating.
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January 23, 2019, 01:09 |
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#3 |
Member
madz
Join Date: Sep 2018
Posts: 34
Rep Power: 7 |
now when i tried this same setup in another system having openfoam and calculated the forces i got correct values.
so it means that there is no problem in the above code or setup but something the way openfoam is calculating in the previous system. I am no expert so someone help me why is it happening |
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