turbGen.C

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/*---------------------------------------------------------------------------*\
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#include <randomProcesses/fft.H>
#include "turbGen.H"
#include <randomProcesses/Kmesh.H>
#include <OpenFOAM/primitiveFields.H>
#include "Ek.H"
#include <OpenFOAM/mathematicalConstants.H>

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{

// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

// from components
turbGen::turbGen(const Kmesh& k, const scalar EA, const scalar K0)
:
    K(k),
    Ea(EA),
    k0(K0),
    RanGen(label(0))
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

// generate and return a velocity field
vectorField turbGen::U()
{
    scalar pi2=2*mathematicalConstant::pi;

    vectorField s(K.size());
    scalarField rndPhases(K.size());

    forAll(K, i)
    {
        s[i] = RanGen.vector01();
        rndPhases[i] = RanGen.scalar01();
    }

    s = K ^ s;
    s = s/(mag(s) + 1.0e-20);

    s = Ek(Ea, k0, mag(K))*s;

    complexVectorField up = fft::reverseTransform
    (
        ComplexField(cos(pi2*rndPhases)*s, sin(pi2*rndPhases)*s),
        K.nn()
    );

    return ReImSum(up);
}


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace Foam

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