Incorrect lift force in simpleFoam airfoil simulation
 

Hi!

I'm trying to simulate a symmetric NACA-0015 airfoil in 3d using simpleFoam in order to derive forces acting on it.

At 18 degree angle towards wind the results look about right
(+25% for drag force and -25% for lift force) compared to tabular values.
But at 0 degree angle I get roughly equal lift and drag force (lift is Y and drag Z) while I expected to have no lift force at all.

"""
SIMPLE solution converged in 6.95 iterations

forces forces_on_object write:
sum of forces:
pressure : (-0.00244928 -10.9063 -9.32257)
viscous : (1.46895e-05 -0.00138044 -3.18357)
porous : (0 0 0)
"""

Pressure and velocity seem to be equal above and below the profile (see attached images).

Any pointer to what I might have missed is much appreciated!

Thanks,
Olov

Hi Olov, your mesh is not good enough. First, mesh needs to much finer. Second, boundary layer mesh is needed. Finally, you better use hex-dominate mesh. Also what turbulence model are you using?

Hi Hokhay!

Thanks for your reply, I'm using kEpsilon RAS and I use snappyHexmesh to generate the mesh. I'll try your suggestions and get back with the results.


"""
simulationType RAS;

RAS
{
RASModel kEpsilon;
turbulence on;
printCoeffs on;
}
"""