Drag/lift force on rising droplet
 

Hello,

I am new and I need to simulate a rising droplet with openfoam (interFoam), it run fine, but I faced a problem when I want to calculate the drag or lift force on the droplet, can anyone help me here please?

I searched the forum but couldn't find the answer (or did I miss it?), anyway I tried to add this code and it worked but as I understand, it is only using for patches (fix/solid boundaries?) and not for a moving droplet:

forces
{
type forces;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;

//patches ( "regions.*" );
patches
(
atmosphere
left
right
wall
);
pName p;
UName U;
rhoName rhoInf;
log true;
rhoInf 1000;
CofR (0.1 0.1 0);
pitchAxis (0 1 0);
}


forcesCoeffs
{
type forceCoeffs;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;

patches
(
atmosphere
left
right
wall
);
pName p;
UName U;
rhoName rhoInf;
log true;
rhoInf 1000;
liftDir (0 1 0); //2D
dragDir (1 0 0);
CofR (0.1 0.1 0);
pitchAxis (0 1 0);
magUInf 0.1;
lRef 1;
Aref 1;
}


So anyone have success with this job or have any idea please shed me a light? It would be really appreciated :)