scalar uStar = (kappa * U) / Foam::log(z1 / z0);

//     Info << "planarAverage" << endl;
        Rw[facei].xx() = 0.0;
        Rw[facei].xy() = 0.0;
        Rw[facei].xz() = -sqr(uStar[facei]) * (UParallel[facei].x() / max(UParallelMeanMag, 1.0E-5));
        Rw[facei].yy() = 0.0;
        Rw[facei].yz() = -sqr(uStar[facei]) * (UParallel[facei].y() / max(UParallelMeanMag, 1.0E-5));
        Rw[facei].zz() = 0.0;