Dear All, I am also trying
 

Dear All,

I am also trying to change the value of the X,Y and Z of U. I add the code in icoFoam.C, but it does not work yet. Could you please help me?

Thanks a lot.
code:
forAll (centers, celli)
{
double angle = 45;
U.component(vector::X) = U.component(vector::X) * Foam::sin(angle);
U.component(vector::Y) = U.component(vector::Y) * Foam::cos(angle);
U.component(vector::Z) = U.component(vector::Z) * 0;
}