turbGen.C

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/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
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-------------------------------------------------------------------------------
    Copyright (C) 2011 OpenFOAM Foundation
    Copyright (C) 2018 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
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\*---------------------------------------------------------------------------*/
 
#include "fft.H"
#include "turbGen.H"
#include "Kmesh.H"
#include "primitiveFields.H"
#include "Ek.H"
#include "mathematicalConstants.H"
 
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
Foam::turbGen::turbGen(const Kmesh& k, const scalar EA, const scalar K0)
:
    K(k),
    Ea(EA),
    k0(K0),
    RanGen(label(0))
{}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
Foam::vectorField Foam::turbGen::U()
{
    vectorField s(K.size());
    scalarField rndPhases(K.size());
 
    forAll(K, i)
    {
        s[i] = RanGen.sample01<vector>();
        rndPhases[i] = RanGen.sample01<scalar>();
    }
 
    s = K ^ s;
    s = s/(mag(s) + 1.0e-20);
 
    s = Ek(Ea, k0, mag(K))*s;
 
    label ntot = 1;
    forAll(K.nn(), idim)
    {
        ntot *= K.nn()[idim];
    }
    const scalar recRootN = 1.0/sqrt(scalar(ntot));
 
    complexVectorField up
    (
        fft::reverseTransform
        (
            ComplexField
            (
                cos(constant::mathematical::twoPi*rndPhases)*s,
                sin(constant::mathematical::twoPi*rndPhases)*s
            ),
            K.nn()
        )*recRootN
    );
 
    return ReImSum(up);
}
 
 
// ************************************************************************* //