indicator.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2020 - 2024 by the ryujin authors
//
 
#pragma once
 
#include "hyperbolic_system.h"
 
#include <compile_time_options.h>
#include <multicomponent_vector.h>
#include <simd.h>
 
#include <deal.II/base/parameter_acceptor.h>
#include <deal.II/base/vectorization.h>
 
 
namespace ryujin
{
  namespace Euler
  {
    template <typename ScalarNumber = double>
    class IndicatorParameters : public dealii::ParameterAcceptor
    {
    public:
      IndicatorParameters(const std::string &subsection = "/Indicator")
          : ParameterAcceptor(subsection)
      {
        evc_factor_ = ScalarNumber(1.);
        add_parameter("evc factor",
                      evc_factor_,
                      "Factor for scaling the entropy viscocity commuator");
      }
 
      ACCESSOR_READ_ONLY(evc_factor);
 
    private:
      ScalarNumber evc_factor_;
    };
 
 
    template <int dim, typename Number = double>
    class Indicator
    {
    public:
      using View = HyperbolicSystemView<dim, Number>;
 
      static constexpr unsigned int problem_dimension = View::problem_dimension;
 
      using precomputed_state_type = typename View::precomputed_state_type;
 
      static constexpr unsigned int n_precomputed_values =
          View::n_precomputed_values;
 
      using state_type = typename View::state_type;
 
      using flux_type = typename View::flux_type;
 
      using ScalarNumber = typename View::ScalarNumber;
 
      using Parameters = IndicatorParameters<ScalarNumber>;
 
 
      Indicator(const HyperbolicSystem &hyperbolic_system,
                const Parameters &parameters,
                const MultiComponentVector<ScalarNumber, n_precomputed_values>
                    &precomputed_values)
          : hyperbolic_system(hyperbolic_system)
          , parameters(parameters)
          , precomputed_values(precomputed_values)
      {
      }
 
      void reset(const unsigned int i, const state_type &U_i);
 
      void accumulate(const unsigned int *js,
                      const state_type &U_j,
                      const dealii::Tensor<1, dim, Number> &c_ij);
 
      Number alpha(const Number h_i) const;
 
 
    private:
 
      const HyperbolicSystem &hyperbolic_system;
      const Parameters &parameters;
 
      const MultiComponentVector<ScalarNumber, n_precomputed_values>
          &precomputed_values;
 
      Number rho_i_inverse = 0.;
      Number eta_i = 0.;
      flux_type f_i;
      state_type d_eta_i;
 
      Number left = 0.;
      state_type right;
 
    };
 
 
    /*
     * -------------------------------------------------------------------------
     * Inline definitions
     * -------------------------------------------------------------------------
     */
 
 
    template <int dim, typename Number>
    DEAL_II_ALWAYS_INLINE inline void
    Indicator<dim, Number>::reset(const unsigned int i, const state_type &U_i)
    {
      /* entropy viscosity commutator: */
 
      const auto view = hyperbolic_system.view<dim, Number>();
 
      const auto &[new_s_i, new_eta_i] =
          precomputed_values
              .template get_tensor<Number, precomputed_state_type>(i);
 
      const auto rho_i = view.density(U_i);
      rho_i_inverse = Number(1.) / rho_i;
      eta_i = new_eta_i;
 
      d_eta_i = view.harten_entropy_derivative(U_i);
      d_eta_i[0] -= eta_i * rho_i_inverse;
      f_i = view.f(U_i);
 
      left = 0.;
      right = 0.;
    }
 
 
    template <int dim, typename Number>
    DEAL_II_ALWAYS_INLINE inline void Indicator<dim, Number>::accumulate(
        const unsigned int *js,
        const state_type &U_j,
        const dealii::Tensor<1, dim, Number> &c_ij)
    {
      /* entropy viscosity commutator: */
 
      const auto view = hyperbolic_system.view<dim, Number>();
 
      const auto &[s_j, eta_j] =
          precomputed_values
              .template get_tensor<Number, precomputed_state_type>(js);
 
      const auto rho_j = view.density(U_j);
      const auto rho_j_inverse = Number(1.) / rho_j;
 
      const auto m_j = view.momentum(U_j);
      const auto f_j = view.f(U_j);
 
      left += (eta_j * rho_j_inverse - eta_i * rho_i_inverse) * (m_j * c_ij);
      for (unsigned int k = 0; k < problem_dimension; ++k)
        right[k] += (f_j[k] - f_i[k]) * c_ij;
    }
 
 
    template <int dim, typename Number>
    DEAL_II_ALWAYS_INLINE inline Number
    Indicator<dim, Number>::alpha(const Number hd_i) const
    {
      using ScalarNumber = typename get_value_type<Number>::type;
 
      Number numerator = left;
      Number denominator = std::abs(left);
      for (unsigned int k = 0; k < problem_dimension; ++k) {
        numerator -= d_eta_i[k] * right[k];
        denominator += std::abs(d_eta_i[k] * right[k]);
      }
 
      const auto quotient =
          std::abs(numerator) / (denominator + hd_i * std::abs(eta_i));
 
      return std::min(Number(1.), parameters.evc_factor() * quotient);
    }
  } // namespace Euler
} // namespace ryujin