| CFD-Lover |
July 1, 2017 16:33 |
drag and lift coefficients in axisymmetric and 3D simulations!
Hi All,
I am working on verifying the drag and lift coefficients using two different simulations (axisymmetric vs. 3D) of the flow over a C-D nozzle. Both simulations converged with four orders of magnitude. In both simulations, I have used the following force function;
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
forces
{
type forces;
functionObjectLibs ("libforces.so");
outputControl timeStep;
outputInterval 1;
patches ( "CDNozzle.*" );
pName p;
UName U;
rhoName rhoInf; // reference density
log true;
CofR (0 0 0); // Center of rotation
rhoInf 1;
}
forceCoeffs
{
type forceCoeffs;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;
patches ( "CDNozzle.*" );
pName p;
UName U;
rhoName rhoInf;
log true;
liftDir (0 1 0); // Direction of lift coefficient
dragDir (1 0 0); // Direction of drag coefficient
CofR (0 0 0);
pitchAxis (0 0 1); //Pitching moment axis
magUInf 8; // Free stream velocity magnitude
rhoInf 1;
lRef 1; //Reference lenght
Aref 1; // Reference area
}
// ************************************************************************* //
After converging, I have got the following values;
3D
Cd Cl
2.139615e-01 -1.042097e-03
Axisymmetric
Cd Cl
2.887599e-03 -3.213962e-03
In the axismmetric results for the drag, I did the following calculations;
Cd = 2.887599e-03*360/5 = 2.07907128e-01 (~3% error), where the value 5 is the wedge angle.
However, the lift coefficient doesn't seem to be right in the axismmetric results :confused:. I am not quite sure what could be the issue here? Anyone has done similar simulation could guide us?
Thanks for your time, |
