void KochHillDrag::setForce
(
    double** const& mask,
    double**& impForces,
    double**& expForces,
    double**& DEMForces
) const
{
    // get viscosity field
    #ifdef comp
        const volScalarField nufField = particleCloud_.turbulence().mu()/rho_;
    #else
        const volScalarField& nufField = particleCloud_.turbulence().nu();
    #endif

    vector position(0,0,0);
    scalar voidfraction(1);
    vector Ufluid(0,0,0);
    vector drag(0,0,0);
    label cellI=0;

    vector Us(0,0,0);
    vector Ur(0,0,0);
    scalar ds(0);
    scalar nuf(0);
    scalar rho(0);
    scalar magUr(0);
    scalar Rep(0);
	scalar Vs(0);
	scalar volumefraction(0);

    interpolationCellPoint<scalar> voidfractionInterpolator_(voidfraction_);
    interpolationCellPoint<vector> UInterpolator_(U_);

    for(int index = 0;index <  particleCloud_.numberOfParticles(); index++)
    {
        if(mask[index][0])
        {

            cellI = particleCloud_.cellIDs()[index][0];
            drag = vector(0,0,0);

            if (cellI > -1) // particle Found
            {
                if(interpolation_)
                {
	                position = particleCloud_.position(index);
                    voidfraction = voidfractionInterpolator_.interpolate(position,cellI);
                    Ufluid = UInterpolator_.interpolate(position,cellI);
                }else
                {
					voidfraction = particleCloud_.voidfraction(index);
                    Ufluid = U_[cellI];
                }

                Us = particleCloud_.velocity(index);
                Ur = Ufluid-Us;
                ds = 2*particleCloud_.radius(index);
                nuf = nufField[cellI];
                rho = rho_[cellI];
                magUr = mag(Ur);
				Rep = 0;
                Vs = ds*ds*ds*M_PI/6;
                volumefraction = 1-voidfraction+SMALL;

                if (magUr > 0)
                {
                    // calc particle Re Nr
                    Rep = ds/scale_*voidfraction*magUr/(nuf+SMALL);

                    // calc model coefficient F0
                    scalar F0=0.;
                    if(volumefraction < 0.4)
                    {
                        F0 = (1+3*sqrt((volumefraction)/2)+135/64*volumefraction*log(volumefraction)+16.14*volumefraction)/
                             (1+0.681*volumefraction-8.48*sqr(volumefraction)+8.16*volumefraction*volumefraction*volumefraction);
                    } else {
                        F0 = 10*volumefraction/(voidfraction*voidfraction*voidfraction);
                    }

                    // calc model coefficient F3
                    scalar F3 = 0.0673+0.212*volumefraction+0.0232/pow(voidfraction,5);

                    // calc model coefficient beta
                    scalar beta = 18*nuf*rho*voidfraction*voidfraction*volumefraction/(ds/scale_*ds/scale_)*
                                  (F0 + 0.5*F3*Rep);

                    // calc particle's drag
                    drag = Vs*beta/volumefraction*Ur;

                    if (modelType_=="B")
                        drag /= voidfraction;
                }

                if(verbose_ && index >=0 && index <2)
                {
                    Info << "index = " << index << endl;
                    Info << "Us = " << Us << endl;
                    Info << "Ur = " << Ur << endl;
                    Info << "ds = " << ds << endl;
                    Info << "ds/scale = " << ds/scale_ << endl;
                    Info << "rho = " << rho << endl;
                    Info << "nuf = " << nuf << endl;
                    Info << "voidfraction = " << voidfraction << endl;
                    Info << "Rep = " << Rep << endl;
                    Info << "drag = " << drag << endl;
                }
            }
            // set force on particle
            if(treatExplicit_) for(int j=0;j<3;j++) expForces[index][j] += drag[j];
            else  for(int j=0;j<3;j++) impForces[index][j] += drag[j];
        }
    }
}
void KochHillDrag::setForce() const
{
    const volScalarField& nufField = forceSubM(0).nuField();
    const volScalarField& rhoField = forceSubM(0).rhoField();


    //update force submodels to prepare for loop
    for (int iFSub=0;iFSub<nrForceSubModels();iFSub++)
        forceSubM(iFSub).preParticleLoop(forceSubM(iFSub).verbose());


    vector position(0,0,0);
    scalar voidfraction(1);
    vector Ufluid(0,0,0);
    vector drag(0,0,0);
    vector dragExplicit(0,0,0);
    scalar dragCoefficient(0);
    label cellI=0;

    vector Us(0,0,0);
    vector Ur(0,0,0);
    scalar ds(0);
    scalar dParcel(0);
    scalar nuf(0);
    scalar rho(0);
    scalar magUr(0);
    scalar Rep(0);
	scalar Vs(0);
	scalar volumefraction(0);
    scalar betaP(0);

    scalar piBySix(M_PI/6);


    int couplingInterval(particleCloud_.dataExchangeM().couplingInterval());

    #include "resetVoidfractionInterpolator.H"
    #include "resetUInterpolator.H"
    #include "setupProbeModel.H"

    for(int index = 0;index <  particleCloud_.numberOfParticles(); index++)
    {
            cellI = particleCloud_.cellIDs()[index][0];
            drag = vector(0,0,0);
            dragExplicit = vector(0,0,0);
            dragCoefficient=0;
            betaP = 0;
            Vs = 0;
            Ufluid =vector(0,0,0);
            voidfraction=0;

            if (cellI > -1) // particle Found
            {
                if(forceSubM(0).interpolation())
                {
	                position = particleCloud_.position(index);
                    voidfraction = voidfractionInterpolator_().interpolate(position,cellI);
                    Ufluid = UInterpolator_().interpolate(position,cellI);

                    //Ensure interpolated void fraction to be meaningful
                    // Info << " --> voidfraction: " << voidfraction << endl;
                    if(voidfraction>1.00) voidfraction = 1.00;
                    if(voidfraction<0.40) voidfraction = 0.40;
                }else
                {
					voidfraction = voidfraction_[cellI];
                    Ufluid = U_[cellI];
                }

                ds = particleCloud_.d(index);
                dParcel = ds;
                forceSubM(0).scaleDia(ds); //caution: this fct will scale ds!
                nuf = nufField[cellI];
                rho = rhoField[cellI];

                Us = particleCloud_.velocity(index);

                //Update any scalar or vector quantity
                for (int iFSub=0;iFSub<nrForceSubModels();iFSub++)
                      forceSubM(iFSub).update(  index,
                                                cellI,
                                                ds,
                                                Ufluid, 
                                                Us, 
                                                nuf,
                                                rho,
                                                forceSubM(0).verbose()
                                             );

                Ur = Ufluid-Us;
                magUr = mag(Ur);
				Rep = 0;

                Vs = ds*ds*ds*piBySix;

                volumefraction = max(SMALL,min(1-SMALL,1-voidfraction));

                if (magUr > 0)
                {
                    // calc particle Re Nr
                    Rep = ds*voidfraction*magUr/(nuf+SMALL);

                    // calc model coefficient F0
                    scalar F0=0.;
                    if(volumefraction < 0.4)
                    {
                        F0 = (1. + 3.*sqrt((volumefraction)/2.) + (135./64.)*volumefraction*log(volumefraction)
                              + 16.14*volumefraction
                             )/
                             (1+0.681*volumefraction-8.48*sqr(volumefraction)
                              +8.16*volumefraction*volumefraction*volumefraction
                             );
                    } else {
                        F0 = 10*volumefraction/(voidfraction*voidfraction*voidfraction);
                    }

                    // calc model coefficient F3
                    scalar F3 = 0.0673+0.212*volumefraction+0.0232/pow(voidfraction,5);

                    //Calculate F (the factor 0.5 is introduced, since Koch and Hill, ARFM 33:619–47, use the radius
                    //to define Rep, and we use the particle diameter, see vanBuijtenen et al., CES 66:2368–2376.
                    scalar F = voidfraction * (F0 + 0.5*F3*Rep);

                    // calc drag model coefficient betaP
                    betaP = 18.*nuf*rho/(ds*ds)*voidfraction*F;

                    // calc particle's drag
                    dragCoefficient = Vs*betaP;
                    if (modelType_=="B")
                        dragCoefficient /= voidfraction;

                    forceSubM(0).scaleCoeff(dragCoefficient,dParcel);

                    if(forceSubM(0).switches()[7]) // implForceDEMaccumulated=true
                    {
		                //get drag from the particle itself
		                for (int j=0 ; j<3 ; j++) drag[j] = particleCloud_.fAccs()[index][j]/couplingInterval;
                    }else
                    {
                        drag = dragCoefficient * Ur;

                        // explicitCorr
                        for (int iFSub=0;iFSub<nrForceSubModels();iFSub++)
                            forceSubM(iFSub).explicitCorr( drag, 
                                                           dragExplicit,
                                                           dragCoefficient,
                                                           Ufluid, U_[cellI], Us, UsField_[cellI],
                                                           forceSubM(iFSub).verbose()
                                                         );
                    }
                }

                if(forceSubM(0).verbose() && index >=0 && index <2)
                {
                    Pout << "cellI = " << cellI << endl;
                    Pout << "index = " << index << endl;
                    Pout << "Us = " << Us << endl;
                    Pout << "Ur = " << Ur << endl;
                    Pout << "dprim = " << ds << endl;
                    Pout << "rho = " << rho << endl;
                    Pout << "nuf = " << nuf << endl;
                    Pout << "voidfraction = " << voidfraction << endl;
                    Pout << "Rep = " << Rep << endl;
                    Pout << "betaP = " << betaP << endl;
                    Pout << "drag = " << drag << endl;
                }

                //Set value fields and write the probe
                if(probeIt_)
                {
                    #include "setupProbeModelfields.H"
                    // Note: for other than ext one could use vValues.append(x)
                    // instead of setSize
                    vValues.setSize(vValues.size()+1, drag);           //first entry must the be the force
                    vValues.setSize(vValues.size()+1, Ur);
                    sValues.setSize(sValues.size()+1, Rep); 
                    sValues.setSize(sValues.size()+1, betaP);
                    sValues.setSize(sValues.size()+1, voidfraction);
                    particleCloud_.probeM().writeProbe(index, sValues, vValues);
                }    
            }

            // write particle based data to global array
            forceSubM(0).partToArray(index,drag,dragExplicit,Ufluid,dragCoefficient);
    }
}
void KochHillDrag::setForce() const
{
    if (scaleDia_ > 1)
        Info << "KochHill using scale = " << scaleDia_ << endl;
    else if (particleCloud_.cg() > 1){
        scaleDia_=particleCloud_.cg();
        Info << "KochHill using scale from liggghts cg = " << scaleDia_ << endl;
    }

    // get viscosity field
    #ifdef comp
        const volScalarField nufField = particleCloud_.turbulence().mu()/rho_;
    #else
        const volScalarField& nufField = particleCloud_.turbulence().nu();
    #endif

    vector position(0,0,0);
    scalar voidfraction(1);
    vector Ufluid(0,0,0);
    vector drag(0,0,0);
    label cellI=0;

    vector Us(0,0,0);
    vector Ur(0,0,0);
    scalar ds(0);
    scalar nuf(0);
    scalar rho(0);
    scalar magUr(0);
    scalar Rep(0);
	scalar Vs(0);
	scalar volumefraction(0);
    scalar betaP(0);

    interpolationCellPoint<scalar> voidfractionInterpolator_(voidfraction_);
    interpolationCellPoint<vector> UInterpolator_(U_);

    #include "setupProbeModel.H"

    for(int index = 0;index <  particleCloud_.numberOfParticles(); index++)
    {
        //if(mask[index][0])
        //{
            cellI = particleCloud_.cellIDs()[index][0];
            drag = vector(0,0,0);
            betaP = 0;
            Vs = 0;
            Ufluid =vector(0,0,0);
            voidfraction=0;

            if (cellI > -1) // particle Found
            {
                if(interpolation_)
                {
	                position = particleCloud_.position(index);
                    voidfraction = voidfractionInterpolator_.interpolate(position,cellI);
                    Ufluid = UInterpolator_.interpolate(position,cellI);
                    //Ensure interpolated void fraction to be meaningful
                    // Info << " --> voidfraction: " << voidfraction << endl;
                    if(voidfraction>1.00) voidfraction = 1.00;
                    if(voidfraction<0.40) voidfraction = 0.40;
                }else
                {
					voidfraction = voidfraction_[cellI];
                    Ufluid = U_[cellI];
                }

                Us = particleCloud_.velocity(index);
                Ur = Ufluid-Us;
                ds = particleCloud_.d(index);
                nuf = nufField[cellI];
                rho = rho_[cellI];
                magUr = mag(Ur);
				Rep = 0;
                Vs = ds*ds*ds*M_PI/6;
                volumefraction = 1-voidfraction+SMALL;

                if (magUr > 0)
                {
                    // calc particle Re Nr
                    Rep = ds/scaleDia_*voidfraction*magUr/(nuf+SMALL);

                    // calc model coefficient F0
                    scalar F0=0.;
                    if(volumefraction < 0.4)
                    {
                        F0 = (1+3*sqrt((volumefraction)/2)+135/64*volumefraction*log(volumefraction)
                              +16.14*volumefraction
                             )/
                             (1+0.681*volumefraction-8.48*sqr(volumefraction)
                              +8.16*volumefraction*volumefraction*volumefraction
                             );
                    } else {
                        F0 = 10*volumefraction/(voidfraction*voidfraction*voidfraction);
                    }

                    // calc model coefficient F3
                    scalar F3 = 0.0673+0.212*volumefraction+0.0232/pow(voidfraction,5);

                    //Calculate F
                    scalar F = voidfraction * (F0 + 0.5*F3*Rep);

                    // calc drag model coefficient betaP
                    betaP = 18.*nuf*rho/(ds/scaleDia_*ds/scaleDia_)*voidfraction*F;

                    // calc particle's drag
                    drag = Vs*betaP*Ur*scaleDrag_;

                    if (modelType_=="B")
                        drag /= voidfraction;
                }

                if(verbose_ && index >=0 && index <2)
                {
                    Pout << "cellI = " << cellI << endl;
                    Pout << "index = " << index << endl;
                    Pout << "Us = " << Us << endl;
                    Pout << "Ur = " << Ur << endl;
                    Pout << "ds = " << ds << endl;
                    Pout << "ds/scale = " << ds/scaleDia_ << endl;
                    Pout << "rho = " << rho << endl;
                    Pout << "nuf = " << nuf << endl;
                    Pout << "voidfraction = " << voidfraction << endl;
                    Pout << "Rep = " << Rep << endl;
                    Pout << "betaP = " << betaP << endl;
                    Pout << "drag = " << drag << endl;
                }

                //Set value fields and write the probe
                if(probeIt_)
                {
                    #include "setupProbeModelfields.H"
                    vValues.append(drag);           //first entry must the be the force
                    vValues.append(Ur);
                    sValues.append(Rep);
                    sValues.append(betaP);
                    sValues.append(voidfraction);
                    particleCloud_.probeM().writeProbe(index, sValues, vValues);
                }    
            }
            // set force on particle
            if(treatExplicit_) for(int j=0;j<3;j++) expForces()[index][j] += drag[j];
            else  for(int j=0;j<3;j++) impForces()[index][j] += drag[j];

            // set Cd
            if(implDEM_)
            {
                for(int j=0;j<3;j++) fluidVel()[index][j]=Ufluid[j];

                if (modelType_=="B" && cellI > -1)
                    Cds()[index][0] = Vs*betaP/voidfraction*scaleDrag_;
                else
                    Cds()[index][0] = Vs*betaP*scaleDrag_;

            }else{
                for(int j=0;j<3;j++) DEMForces()[index][j] += drag[j];
            }

        //}
    }
}