Program Listing for File Viscosity_Standard.cpp

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#include "Viscosity_Standard.h"
#include "SPlisHSPlasH/TimeManager.h"
#include "../Simulation.h"
#include "SPlisHSPlasH/BoundaryModel_Akinci2012.h"
#include "SPlisHSPlasH/BoundaryModel_Koschier2017.h"
#include "SPlisHSPlasH/BoundaryModel_Bender2019.h"
#include "SPlisHSPlasH/Utilities/MathFunctions.h"


using namespace SPH;
using namespace GenParam;

int Viscosity_Standard::VISCOSITY_COEFFICIENT_BOUNDARY = -1;


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

Viscosity_Standard::~Viscosity_Standard(void)
{
}

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

    VISCOSITY_COEFFICIENT_BOUNDARY = createNumericParameter("viscosityBoundary", "Viscosity coefficient (Boundary)", &m_boundaryViscosity);
    setGroup(VISCOSITY_COEFFICIENT_BOUNDARY, "Fluid Model|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);
}

#ifdef USE_AVX

void Viscosity_Standard::step()
{
    Simulation *sim = Simulation::getCurrent();
    const unsigned int numParticles = m_model->numActiveParticles();
    const Real h = sim->getSupportRadius();
    const Real h2 = h*h;
    const Real sphereVolume = static_cast<Real>(4.0 / 3.0 * M_PI) * h2*h;
    const unsigned int nFluids = sim->numberOfFluidModels();
    const unsigned int nBoundaries = sim->numberOfBoundaryModels();
    const unsigned int fluidModelIndex = m_model->getPointSetIndex();
    const Real density0 = m_model->getDensity0();
    FluidModel *model = m_model;
    Real d = 10.0;
    if (sim->is2DSimulation())
        d = 8.0;

    const Scalarf8 dvisc(d * m_viscosity * density0);
    const Scalarf8 dbvisc(d * m_boundaryViscosity);
    const Scalarf8 h2_avx(0.01f*h2);
    const Scalarf8 density0_avx(density0);

    #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);

            const Vector3f8 xi_avx(xi);
            const Vector3f8 vi_avx(vi);
            const Scalarf8 mi_avx(m_model->getMass(i));
            const Scalarf8 density_i_avx(density_i);

            Vector3f8 delta_ai;
            delta_ai.setZero();

            // Fluid
            forall_fluid_neighbors_in_same_phase_avx(
                compute_Vj(model);
                compute_Vj_gradW_samephase();
                const Vector3f8 vj_avx = convertVec_zero(&sim->getNeighborList(fluidModelIndex, fluidModelIndex, i)[j], &model->getVelocity(0), count);

                // Viscosity
                const Scalarf8 density_j_avx = convert_one(&sim->getNeighborList(fluidModelIndex, fluidModelIndex, i)[j], &model->getDensity(0), count);
                const Vector3f8 xixj = xi_avx - xj_avx;
                delta_ai += V_gradW * ((dvisc / density_j_avx) * (vi_avx - vj_avx).dot(xixj) / (xixj.squaredNorm() + h2_avx));
            );

            // Boundary
            if (m_boundaryViscosity != 0.0)
            {
                if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
                {
                    forall_boundary_neighbors_avx(
                        const Vector3f8 vj_avx = convertVec_zero(&sim->getNeighborList(fluidModelIndex, pid, i)[j], &bm_neighbor->getVelocity(0), count);
                        const Scalarf8 Vj_avx = convert_zero(&sim->getNeighborList(fluidModelIndex, pid, i)[j], &bm_neighbor->getVolume(0), count);
                        const Vector3f8 xixj = xi_avx - xj_avx;
                        const Vector3f8 delta_a = CubicKernel_AVX::gradW(xixj) * (dbvisc * (density0_avx * Vj_avx / density_i_avx) * (vi_avx - vj_avx).dot(xixj) / (xixj.squaredNorm() + h2_avx));
                        delta_ai += delta_a;
                        bm_neighbor->addForce(xj_avx, -delta_a * mi_avx, count);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                {
                    forall_density_maps(
                        const Vector3r xixj = xi - xj;
                        Vector3r normal = -xixj;
                        const Real nl = normal.norm();
                        if (nl > static_cast<Real>(0.0001))
                        {
                            normal /= nl;

                            Vector3r t1;
                            Vector3r t2;
                            MathFunctions::getOrthogonalVectors(normal, t1, t2);

                            const Real dist = (static_cast<Real>(1.0) - nl / h) * h;
                            //const Real dist = 0.5*h;
                            const Vector3r x1 = xj - t1*dist;
                            const Vector3r x2 = xj + t1*dist;
                            const Vector3r x3 = xj - t2*dist;
                            const Vector3r x4 = xj + t2*dist;

                            const Vector3r xix1 = xi - x1;
                            const Vector3r xix2 = xi - x2;
                            const Vector3r xix3 = xi - x3;
                            const Vector3r xix4 = xi - x4;

                            const Vector3r gradW1 = sim->gradW(xix1);
                            const Vector3r gradW2 = sim->gradW(xix2);
                            const Vector3r gradW3 = sim->gradW(xix3);
                            const Vector3r gradW4 = sim->gradW(xix4);

                            // each sample point represents the quarter of the volume inside of the boundary
                            const Real vol = static_cast<Real>(0.25) * rho * sphereVolume;

                            Vector3r v1;
                            Vector3r v2;
                            Vector3r v3;
                            Vector3r v4;
                            bm_neighbor->getPointVelocity(x1, v1);
                            bm_neighbor->getPointVelocity(x2, v2);
                            bm_neighbor->getPointVelocity(x3, v3);
                            bm_neighbor->getPointVelocity(x4, v4);

                            // compute forces for both sample point
                            const Vector3r a1 = (d * m_boundaryViscosity * vol * (vi - v1).dot(xix1) / (xix1.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW1;
                            const Vector3r a2 = (d * m_boundaryViscosity * vol * (vi - v2).dot(xix2) / (xix2.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW2;
                            const Vector3r a3 = (d * m_boundaryViscosity * vol * (vi - v3).dot(xix3) / (xix3.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW3;
                            const Vector3r a4 = (d * m_boundaryViscosity * vol * (vi - v4).dot(xix4) / (xix4.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW4;
                            ai += a1 + a2 + a3 + a4;

                            bm_neighbor->addForce(x1, -m_model->getMass(i) * a1);
                            bm_neighbor->addForce(x2, -m_model->getMass(i) * a2);
                            bm_neighbor->addForce(x3, -m_model->getMass(i) * a3);
                            bm_neighbor->addForce(x4, -m_model->getMass(i) * a4);
                        }
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                {
                    forall_volume_maps(
                        const Vector3r xixj = xi - xj;
                        Vector3r normal = -xixj;
                        const Real nl = normal.norm();
                        if (nl > static_cast<Real>(0.0001))
                        {
                            normal /= nl;

                            Vector3r t1;
                            Vector3r t2;
                            MathFunctions::getOrthogonalVectors(normal, t1, t2);

                            const Real dist = (static_cast<Real>(1.0) - nl / h) * h;
                            //const Real dist = 0.5*h;
                            const Vector3r x1 = xj - t1*dist;
                            const Vector3r x2 = xj + t1*dist;
                            const Vector3r x3 = xj - t2*dist;
                            const Vector3r x4 = xj + t2*dist;

                            const Vector3r xix1 = xi - x1;
                            const Vector3r xix2 = xi - x2;
                            const Vector3r xix3 = xi - x3;
                            const Vector3r xix4 = xi - x4;

                            const Vector3r gradW1 = sim->gradW(xix1);
                            const Vector3r gradW2 = sim->gradW(xix2);
                            const Vector3r gradW3 = sim->gradW(xix3);
                            const Vector3r gradW4 = sim->gradW(xix4);

                            // each sample point represents the quarter of the volume inside of the boundary
                            const Real vol = static_cast<Real>(0.25) * Vj;

                            Vector3r v1;
                            Vector3r v2;
                            Vector3r v3;
                            Vector3r v4;
                            bm_neighbor->getPointVelocity(x1, v1);
                            bm_neighbor->getPointVelocity(x2, v2);
                            bm_neighbor->getPointVelocity(x3, v3);
                            bm_neighbor->getPointVelocity(x4, v4);

                            // compute forces for both sample point
                            const Vector3r a1 = (d * m_boundaryViscosity * vol * (vi - v1).dot(xix1) / (xix1.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW1;
                            const Vector3r a2 = (d * m_boundaryViscosity * vol * (vi - v2).dot(xix2) / (xix2.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW2;
                            const Vector3r a3 = (d * m_boundaryViscosity * vol * (vi - v3).dot(xix3) / (xix3.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW3;
                            const Vector3r a4 = (d * m_boundaryViscosity * vol * (vi - v4).dot(xix4) / (xix4.squaredNorm() + static_cast<Real>(0.01)*h2)) * gradW4;
                            ai += a1 + a2 + a3 + a4;

                            bm_neighbor->addForce(x1, -m_model->getMass(i) * a1);
                            bm_neighbor->addForce(x2, -m_model->getMass(i) * a2);
                            bm_neighbor->addForce(x3, -m_model->getMass(i) * a3);
                            bm_neighbor->addForce(x4, -m_model->getMass(i) * a4);
                        }
                    );
                }
            }

            ai[0] += delta_ai.x().reduce();
            ai[1] += delta_ai.y().reduce();
            ai[2] += delta_ai.z().reduce();
        }
    }
}

#else

void Viscosity_Standard::step()
{
    Simulation *sim = Simulation::getCurrent();
    const unsigned int numParticles = m_model->numActiveParticles();
    const Real h = sim->getSupportRadius();
    const Real h2 = h*h;
    const Real sphereVolume = static_cast<Real>(4.0 / 3.0 * M_PI) * h2*h;
    const unsigned int nFluids = sim->numberOfFluidModels();
    const unsigned int nBoundaries = sim->numberOfBoundaryModels();
    const unsigned int fluidModelIndex = m_model->getPointSetIndex();
    const Real density0 = m_model->getDensity0();
    FluidModel *model = m_model;
    Real d = 10.0;
    if (sim->is2DSimulation())
        d = 8.0;

    #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_in_same_phase(
                const Vector3r &vj = model->getVelocity(neighborIndex);

                // Viscosity
                const Real density_j = model->getDensity(neighborIndex);
                const Vector3r xixj = xi - xj;
                ai += d * m_viscosity * (model->getMass(neighborIndex) / density_j) * (vi - vj).dot(xixj) / (xixj.squaredNorm() + 0.01*h2) * sim->gradW(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 xixj = xi - xj;
                        const Vector3r a = d * m_boundaryViscosity * (density0 * bm_neighbor->getVolume(neighborIndex) / density_i) * (vi - vj).dot(xixj) / (xixj.squaredNorm() + 0.01*h2) * sim->gradW(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                {
                    forall_density_maps(
                        const Vector3r xixj = xi - xj;
                        Vector3r normal = -xixj;
                        const Real nl = normal.norm();
                        if (nl > static_cast<Real>(0.0001))
                        {
                            normal /= nl;

                            Vector3r t1;
                            Vector3r t2;
                            MathFunctions::getOrthogonalVectors(normal, t1, t2);

                            const Real dist = (static_cast<Real>(1.0) - nl / h) * h;
                            //const Real dist = 0.25*h;
                            const Vector3r x1 = xj - t1*dist;
                            const Vector3r x2 = xj + t1*dist;
                            const Vector3r x3 = xj - t2*dist;
                            const Vector3r x4 = xj + t2*dist;

                            const Vector3r xix1 = xi - x1;
                            const Vector3r xix2 = xi - x2;
                            const Vector3r xix3 = xi - x3;
                            const Vector3r xix4 = xi - x4;

                            const Vector3r gradW1 = sim->gradW(xix1);
                            const Vector3r gradW2 = sim->gradW(xix2);
                            const Vector3r gradW3 = sim->gradW(xix3);
                            const Vector3r gradW4 = sim->gradW(xix4);

                            // each sample point represents the quarter of the volume inside of the boundary
                            const Real vol = static_cast<Real>(0.25) * rho * sphereVolume;

                            Vector3r v1;
                            Vector3r v2;
                            Vector3r v3;
                            Vector3r v4;
                            bm_neighbor->getPointVelocity(x1, v1);
                            bm_neighbor->getPointVelocity(x2, v2);
                            bm_neighbor->getPointVelocity(x3, v3);
                            bm_neighbor->getPointVelocity(x4, v4);

                            // compute forces for both sample point
                            const Vector3r a1 = d * m_boundaryViscosity * vol * (vi - v1).dot(xix1) / (xix1.squaredNorm() + 0.01*h2) * gradW1;
                            const Vector3r a2 = d * m_boundaryViscosity * vol * (vi - v2).dot(xix2) / (xix2.squaredNorm() + 0.01*h2) * gradW2;
                            const Vector3r a3 = d * m_boundaryViscosity * vol * (vi - v3).dot(xix3) / (xix3.squaredNorm() + 0.01*h2) * gradW3;
                            const Vector3r a4 = d * m_boundaryViscosity * vol * (vi - v4).dot(xix4) / (xix4.squaredNorm() + 0.01*h2) * gradW4;
                            ai += a1 + a2 + a3 + a4;

                            bm_neighbor->addForce(x1, -m_model->getMass(i) * a1);
                            bm_neighbor->addForce(x2, -m_model->getMass(i) * a2);
                            bm_neighbor->addForce(x3, -m_model->getMass(i) * a3);
                            bm_neighbor->addForce(x4, -m_model->getMass(i) * a4);
                        }
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                {
                    forall_volume_maps(
                        const Vector3r xixj = xi - xj;
                        Vector3r normal = -xixj;
                        const Real nl = normal.norm();
                        if (nl > static_cast<Real>(0.0001))
                        {
                            normal /= nl;

                            Vector3r t1;
                            Vector3r t2;
                            MathFunctions::getOrthogonalVectors(normal, t1, t2);

                            const Real dist = (static_cast<Real>(1.0) - nl / h) * h;
                            //const Real dist = 0.25*h;
                            const Vector3r x1 = xj - t1*dist;
                            const Vector3r x2 = xj + t1*dist;
                            const Vector3r x3 = xj - t2*dist;
                            const Vector3r x4 = xj + t2*dist;

                            const Vector3r xix1 = xi - x1;
                            const Vector3r xix2 = xi - x2;
                            const Vector3r xix3 = xi - x3;
                            const Vector3r xix4 = xi - x4;

                            const Vector3r gradW1 = sim->gradW(xix1);
                            const Vector3r gradW2 = sim->gradW(xix2);
                            const Vector3r gradW3 = sim->gradW(xix3);
                            const Vector3r gradW4 = sim->gradW(xix4);

                            // each sample point represents the quarter of the volume inside of the boundary
                            const Real vol = static_cast<Real>(0.25) * Vj;

                            Vector3r v1;
                            Vector3r v2;
                            Vector3r v3;
                            Vector3r v4;
                            bm_neighbor->getPointVelocity(x1, v1);
                            bm_neighbor->getPointVelocity(x2, v2);
                            bm_neighbor->getPointVelocity(x3, v3);
                            bm_neighbor->getPointVelocity(x4, v4);

                            // compute forces for both sample point
                            const Vector3r a1 = d * m_boundaryViscosity * vol * (vi - v1).dot(xix1) / (xix1.squaredNorm() + 0.01*h2) * gradW1;
                            const Vector3r a2 = d * m_boundaryViscosity * vol * (vi - v2).dot(xix2) / (xix2.squaredNorm() + 0.01*h2) * gradW2;
                            const Vector3r a3 = d * m_boundaryViscosity * vol * (vi - v3).dot(xix3) / (xix3.squaredNorm() + 0.01*h2) * gradW3;
                            const Vector3r a4 = d * m_boundaryViscosity * vol * (vi - v4).dot(xix4) / (xix4.squaredNorm() + 0.01*h2) * gradW4;
                            ai += a1 + a2 + a3 + a4;

                            bm_neighbor->addForce(x1, -m_model->getMass(i) * a1);
                            bm_neighbor->addForce(x2, -m_model->getMass(i) * a2);
                            bm_neighbor->addForce(x3, -m_model->getMass(i) * a3);
                            bm_neighbor->addForce(x4, -m_model->getMass(i) * a4);
                        }
                    );
                }
            }
        }
    }
}

#endif

void Viscosity_Standard::reset()
{
}