data/tutorials/shockFluid/diffuserIntake/system/skinFrictionCoeff

// Description
//   Calculates skin friction coefficient (Cf) from the wallShearStress

libs     ("libutilityFunctionObjects.so");
type     coded;
writeControl writeTime;

magU      ${${FOAM_CASE}/0/U!Uinlet};
M         ${${FOAM_CASE}/constant/physicalProperties!mixture/specie/molWeight};
pInf      ${${FOAM_CASE}/0/p!pInlet};
TInf      ${${FOAM_CASE}/0/T!Tinlet};

codeInclude
#{
    #include "constants.H"
    using namespace Foam::constant::thermodynamic;
#};

codeOptions
#{
    -I$(LIB_SRC)/finiteVolume/lnInclude
#};

codeFields
#{
    fields.append("wallShearStress");
#};

codeWrite
#{
    const scalar R = RR / $M;
    const scalar rhoInf = $pInf / (R*$TInf);

    const volVectorField& wallShearStress =
        mesh().lookupObject<volVectorField>("wallShearStress");

    volScalarField Cf
    (
        "Cf",
        (wallShearStress & vector(-1, 0, 0))
       /dimensionedScalar(wallShearStress.dimensions(), 0.5*rhoInf*sqr($magU))
    );

    Cf.write();
#};