solvers/APESolver/RiemannSolvers/UpwindSolver.cpp

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///////////////////////////////////////////////////////////////////////////////
//
// File: UpwindSolver.cpp
//
// For more information, please see: http://www.nektar.info
//
// The MIT License
//
// Copyright (c) 2014 Kilian Lackhove
// Copyright (c) 2006 Division of Applied Mathematics, Brown University (USA),
// Department of Aeronautics, Imperial College London (UK), and Scientific
// Computing and Imaging Institute, University of Utah (USA).
//
// License for the specific language governing rights and limitations under
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// DEALINGS IN THE SOFTWARE.
//
// Description: Upwind Riemann solver for the APE equations.
//
///////////////////////////////////////////////////////////////////////////////

#include <APESolver/RiemannSolvers/UpwindSolver.h>

using namespace std;

namespace Nektar
{

std::string UpwindSolver::solverName = SolverUtils::GetRiemannSolverFactory().
        RegisterCreatorFunction("APEUpwind", UpwindSolver::create, "Upwind solver for the APE equation");

UpwindSolver::UpwindSolver() :
    APESolver()
{

}


/**
 * @brief Upwind Riemann solver
 *
 * @param pL     Perturbation pressure left state.
 * @param pR     Perturbation pressure right state.
 * @param uL     x perturbation verlocity component left state.
 * @param uR     x perturbation verlocity component right state.
 * @param vL     y perturbation verlocity component left state.
 * @param vR     y perturbation verlocity component right state.
 * @param wL     z perturbation verlocity component left state.
 * @param wR     z perturbation verlocity component right state.
 * @param p0     Base pressure.
 * @param u0     Base x verlocity component
 * @param v0     Base y verlocity component
 * @param w0     Base z verlocity component
 * @param pF     Computed Riemann flux for perturbation pressure.
 * @param uF     Computed Riemann flux for x perturbation verlocity component
 * @param vF     Computed Riemann flux for y perturbation verlocity component
 * @param wF     Computed Riemann flux for z perturbation verlocity component
 */
void UpwindSolver::v_PointSolve(
    NekDouble  pL, NekDouble  uL, NekDouble  vL, NekDouble  wL,
    NekDouble  pR, NekDouble  uR, NekDouble  vR, NekDouble  wR,
    NekDouble  p0, NekDouble  u0, NekDouble  v0, NekDouble  w0,
    NekDouble &pF, NekDouble &uF, NekDouble &vF, NekDouble &wF)
{
    // fetch params
    ASSERTL1(CheckParams("Gamma"), "Gamma not defined.");
    ASSERTL1(CheckParams("Rho"), "Rho not defined.");
    const NekDouble &gamma= m_params["Gamma"]();
    const NekDouble &rho = m_params["Rho"]();

    Array<OneD, NekDouble> characteristic(4);
    Array<OneD, NekDouble> W(2);
    Array<OneD, NekDouble> lambda(2);

    // compute the wave speeds
    lambda[0]=u0 + sqrt(p0*gamma*rho)/rho;
    lambda[1]=u0 - sqrt(p0*gamma*rho)/rho;

    // calculate the caracteristic variables
    //left characteristics
    characteristic[0] = pL/2 + uL*sqrt(p0*gamma*rho)/2;
    characteristic[1] = pL/2 - uL*sqrt(p0*gamma*rho)/2;
    //right characteristics
    characteristic[2] = pR/2 + uR*sqrt(p0*gamma*rho)/2;
    characteristic[3] = pR/2 - uR*sqrt(p0*gamma*rho)/2;

    //take left or right value of characteristic variable
    for (int j = 0; j < 2; j++)
    {
        if (lambda[j]>=0)
        {
            W[j]=characteristic[j];
        }
        if(lambda[j]<0)
        {
            W[j]=characteristic[j+2];
        }
    }

    //calculate conservative variables from characteristics
    NekDouble p = W[0]+W[1];
    NekDouble u = (W[0]-W[1])/sqrt(p0*gamma*rho);
    // do not divide by zero
    if (p0*gamma*rho == 0)
    {
        u = 0.0;
    }

    // assemble the fluxes
    pF = gamma*p0 * u + u0*p;
    uF = p/rho + u0*u + v0*vL + w0*wL;
    vF = 0.0;
    wF = 0.0;
}

}