[mqsim]

Hi everyone,

I am confused with the density used in simpleFoam. I need to determine precisely the lift of a building.

I am trying to understand how drag and lift coefficients are calculated using forceCoeffs. In forceCoeffs.C, rhoRef is used instead of rhoInf and rhoRef is not a constant defined in the forceCoeffs file.

My kinematic viscosity is 1.4607e-05 m2/s which gives me a density of 1.225 kg/m3. Then, the lift coefficient given by OpenFoam is 2.30356. But when I use the pressure and viscous force values to determine the lift coefficient by myself I find 1.880459=2.30356/1.225. When I put rhoInf=1.225 tor rhoInf=1.00 here is no modification.

It seems the division by the density in the lift coefficient calculation is not done. Does anyone have this problem?

Furthermore, my stagnation pressure obtained after calculation seems to be the pressure and not the pressure divided by the density. I know that the pressure in simpleFoam is P/rho, so I don't understand why I have this pressure in my case.

Regards,

mqsim