body force with a phase shift
 

Hello,
I would like to add body force to my 2D equation:
F(x,z,t)= F0(x,z)*cos(wt- z/d)^2, where
F0(x,z) - the matrix with constant coefficients, which is reading from file,
w - constant frequency, d - constant,
and x,z - coordinates.
I have some trouble with phase shift term in cos(wt- z/d).
How I can get z - coordinate?

Without the term responsible for the phase shift I have next code, It's works:

volVectorField F
(
IOobject
(
"F",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);


volVectorField F1
(
IOobject
(
"F1",
runTime.timeName(),
mesh,
IOobject::NO_READ,
IOobject::AUTO_WRITE
),
F*pow((Foam::cos(2*M_PI*5*runTime.value())),2)
);