[keepfit]

Hi Foamers,

I want to test the drag coefficient of regular (e.g. sphere) and irregular objects using the CFD method.

The problem is that how to calculate the fluid force acting the Object.

A still sphere is in the fluid and the velocity and pressure field are solved (currently pimpleFoam):



The resulting force would be: (assuming the sphere has N sub-surfaces, treated as wall)

F_fluild = Sum(Pi * Ai* n), i = 1, 2, .... N

where Pi/AI- pressure/area of ith surface of the sphere/obstacle, n the normal of ith surface .

If we subtract buoyancy force Fb from F_fluid,

F_(drag/life) = F_fluid - Fb

The issue is: how to loop on the certain boundary and access the pressure or velocity information on this boundary (object/obstacle).


Any tips or recommendation would be highly appreciated.

thanks in advance!

[tomf]

I would suggest to use the forces and forceCoeffs functionObjects. There are many threads on this forum that discuss it....

[keepfit]

Originally Posted by tomf

I would suggest to use the forces and forceCoeffs functionObjects. There are many threads on this forum that discuss it....

thanks tomf, I will give a try on the library fucntions.