a problem in drag coefficient calculating
 

Hello foamers;
I want to calculate drag coefficient on each walls of a cube with unit dimension which is located in a flat plate. The inlet velocity components are (1,0,0) and the density of fluid is 0.1; I add the following code to controlDict :
functions
{ forces
{
type forceCoeffs;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;
patches
(
top
);
pName p;
UName U;
log true;
rhoInf 0.1;
CofR (0 0 0 );
liftDir ( 0 0 0 );
dragDir ( 1 0 0 );
pitchAxis ( 0 0 0 );
magUInf 1;
lRef 1;
Aref 1;
}
}
But the result isn't true. Would you tell me the mistake?
Thanks;

Cd calculation
 

Hi
Do you use OpenFoam software for your simulation?