[paul_oborin]

Hello everyone,
I'm a new OpenFoam user.
I need to add into the Navier-Stokes equations the time-dependent force: f(t) = F*cos(w*t)^2, where t - time.

Here is the UEqn.H:

fvVectorMatrix UEqn
    (
        fvm::ddt(rho, U)
      + fvm::div(rhoPhi, U)
      + turbulence->divDevRhoReff(rho, U)
    );

    UEqn.relax();

    if (pimple.momentumPredictor())
    {
        solve
        (
            UEqn
         ==
           (rho*F) - fvc::reconstruct
            (
                (
                  - ghf*fvc::snGrad(rho)
                  - fvc::snGrad(p_rgh)
                ) * mesh.magSf()
            )
        );
    }

createFields.H

...
Info<< "Reading field F\n" << endl;
volVectorField F
(
IOobject
(
"F",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);
...

It's work for f=F without t, but I don't know how write t and F*cos(w*t)^2.
Could you tell me how to do it.