Program Listing for File Viscosity_XSPH.cpp

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#include "Viscosity_XSPH.h"
#include "SPlisHSPlasH/TimeManager.h"
#include "../Simulation.h"
#include "SPlisHSPlasH/BoundaryModel_Akinci2012.h"
#include "SPlisHSPlasH/BoundaryModel_Koschier2017.h"
#include "SPlisHSPlasH/BoundaryModel_Bender2019.h"

using namespace SPH;
using namespace GenParam;

int Viscosity_XSPH::VISCOSITY_COEFFICIENT_BOUNDARY = -1;


Viscosity_XSPH::Viscosity_XSPH(FluidModel *model) :
    ViscosityBase(model)
{
    m_boundaryViscosity = 0.0;
}

Viscosity_XSPH::~Viscosity_XSPH(void)
{
}

void Viscosity_XSPH::initParameters()
{
    ViscosityBase::initParameters();

    VISCOSITY_COEFFICIENT_BOUNDARY = createNumericParameter("viscosityBoundary", "Viscosity coefficient (Boundary)", &m_boundaryViscosity);
    setGroup(VISCOSITY_COEFFICIENT_BOUNDARY, "Viscosity");
    setDescription(VISCOSITY_COEFFICIENT_BOUNDARY, "Coefficient for the viscosity force computation at the boundary.");
    RealParameter* rparam = static_cast<RealParameter*>(getParameter(VISCOSITY_COEFFICIENT_BOUNDARY));
    rparam->setMinValue(0.0);
}

void Viscosity_XSPH::step()
{
    Simulation *sim = Simulation::getCurrent();
    const unsigned int nFluids = sim->numberOfFluidModels();
    const unsigned int nBoundaries = sim->numberOfBoundaryModels();
    const unsigned int fluidModelIndex = m_model->getPointSetIndex();
    const unsigned int numParticles = m_model->numActiveParticles();
    const Real density0 = m_model->getValue<Real>(FluidModel::DENSITY0);

    const Real h = TimeManager::getCurrent()->getTimeStepSize();
    const Real invH = (static_cast<Real>(1.0) / h);

    // Compute viscosity forces (XSPH)
    #pragma omp parallel default(shared)
    {
        #pragma omp for schedule(static)
        for (int i = 0; i < (int)numParticles; i++)
        {
            const Vector3r &xi = m_model->getPosition(i);
            const Vector3r &vi = m_model->getVelocity(i);
            Vector3r &ai = m_model->getAcceleration(i);
            const Real density_i = m_model->getDensity(i);

            // Fluid
            forall_fluid_neighbors(
                const Vector3r &vj = fm_neighbor->getVelocity(neighborIndex);

                // Viscosity
                const Real density_j = fm_neighbor->getDensity(neighborIndex);
                ai -= invH * m_viscosity * (fm_neighbor->getMass(neighborIndex) / density_j) * (vi - vj) * sim->W(xi - xj);
            );

            // Boundary
            if (m_boundaryViscosity != 0.0)
            {
                if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
                {
                    forall_boundary_neighbors(
                        const Vector3r &vj = bm_neighbor->getVelocity(neighborIndex);
                        const Vector3r a = -invH * m_boundaryViscosity * (density0 * bm_neighbor->getVolume(neighborIndex) / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                {
                    forall_density_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xi, vj);
                        const Vector3r a = -invH * m_boundaryViscosity * (density0 / density_i) * (vi-vj)* rho;
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                {
                    forall_volume_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xj, vj);
                        const Vector3r a = -invH * m_boundaryViscosity * (density0 * Vj / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
            }
        }
    }
}


void Viscosity_XSPH::reset()
{
}