foam-extend4.1-coherent-io/applications/solvers/incompressible/simpleFoam/UEqn.H

    // Solve the momentum equation

    tmp<fvVectorMatrix> UEqn
    (
        fvm::div(phi, U)
      + turbulence->divDevReff(U)
    );

    UEqn().relax();

    eqnResidual = solve
    (
        UEqn() == -fvc::grad(p)
    ).initialResidual();

    maxResidual = max(eqnResidual, maxResidual);