foam-extend4.1-coherent-io/applications/solvers/coupled/pUCoupledFoam/UEqn.H

{
    // Momentum equation
    fvVectorMatrix UEqn
    (
        fvm::ddt(U)
      + fvm::div(phi, U)
      + turbulence->divDevReff()
    );

    rAU = 1.0/UEqn.A();

    if (gMin(rAU) < 0)
    {
        WarningIn(args.executable())
            << "Negative rAU detected.  Check mesh and discretisation"
            << endl;
    }
    
    // Under-relax momentum. Note this will destroy the H and A
    UEqn.relax();

    // Insert momentum equation
    UpEqn.insertEquation(0, UEqn);

#   include "addBlockCoupledBC.H"
}