BrownianMotionForce.C

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#include "BrownianMotionForce.H"
#include "mathematicalConstants.H"
#include "fundamentalConstants.H"
#include "demandDrivenData.H"
#include "momentumTransportModel.H"
#include "standardNormal.H"
 
using namespace Foam::constant;
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
template<class CloudType>
Foam::BrownianMotionForce<CloudType>::BrownianMotionForce
(
    CloudType& owner,
    const fvMesh& mesh,
    const dictionary& dict
)
:
    ParticleForce<CloudType>(owner, mesh, dict, typeName, true),
    lambda_(this->coeffs().template lookup<scalar>("lambda"))
{}
 
 
template<class CloudType>
Foam::BrownianMotionForce<CloudType>::BrownianMotionForce
(
    const BrownianMotionForce& bmf
)
:
    ParticleForce<CloudType>(bmf),
    lambda_(bmf.lambda_)
{}
 
 
// * * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * //
 
template<class CloudType>
Foam::BrownianMotionForce<CloudType>::~BrownianMotionForce()
{}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
template<class CloudType>
Foam::forceSuSp Foam::BrownianMotionForce<CloudType>::calcCoupled
(
    const typename CloudType::parcelType& p,
    const typename CloudType::parcelType::trackingData& td,
    const scalar dt,
    const scalar mass,
    const scalar Re,
    const scalar muc
) const
{
    forceSuSp value(Zero, 0.0);
 
    const scalar dp = p.d();
    const scalar Tc = td.Tc();
 
    const scalar alpha = 2.0*lambda_/dp;
    const scalar cc = 1.0 + alpha*(1.257 + 0.4*exp(-1.1/alpha));
 
    // Boltzmann constant
    const scalar kb = physicoChemical::k.value();
 
    // Equation 25
    const scalar s0 =
        216*muc*kb*Tc/(sqr(mathematical::pi)*pow5(dp)*sqr(p.rho())*cc);
 
    // Equation 26
    const scalar f = mass*sqrt(mathematical::pi*s0/dt);
 
    randomGenerator& rndGen = this->owner().rndGen();
    distributions::standardNormal& stdNormal = this->owner().stdNormal();
 
    // To generate a cubic distribution (i.e., 3 independent directions):
    // value.Su() = f*stdNormal.sample<vector>();
 
    // To generate a spherical distribution:
    const scalar theta = rndGen.scalar01()*mathematical::twoPi;
    const scalar u = 2*rndGen.scalar01() - 1;
    const scalar a = sqrt(1 - sqr(u));
    const vector dir(a*cos(theta), a*sin(theta), u);
    value.Su() = f*mag(stdNormal.sample())*dir;
 
    return value;
}
 
 
// ************************************************************************* //