[immortality]

its the momemntum equation in rhoCentralFoam.
what are equivalents for its terms in CFD form?

solve
            (
                fvm::ddt(rho, U) - fvc::ddt(rho, U)
              - fvm::laplacian(muEff, U)
              - fvc::div(tauMC)
            );

in rhoPimpleFoam its so:

tmp<fvVectorMatrix> UEqn
(
    fvm::ddt(rho, U)
  + fvm::div(phi, U)
  + turbulence->divDevRhoReff(U)
 ==
    fvOptions(rho, U)
);

UEqn().relax();

fvOptions.constrain(UEqn());

if (pimple.momentumPredictor())
{
    solve(UEqn() == -fvc::grad(p));

    fvOptions.correct(U);
    K = 0.5*magSqr(U);
}

that the temporal,convection and diffusion and source terms are more clear than in rhoCentralFoam.