Sources_helpers_Multiphase.h

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#ifndef Sources_helpers_Multiphase_included
#define Sources_helpers_Multiphase_included
 
#include <Milieu_composite.h>
#include <Pb_Multiphase.h>
 
#include <algorithm>
#include <cmath>
 
/*! @brief Shared helpers for multiphase source terms and correlations
 *         (surface tension indexing, liquid phase finder, drag, Eotvos, etc.)
 *         used across the CMFD module.
 */
 
/*! @brief Finds the liquid phase index in a multiphase problem.
 *         Prefers a phase named "liquide...continu" if available.
 */
inline int find_liquid_phase(const Pb_Multiphase& pbm, const Nom& class_name)
{
  if (pbm.nb_phases() == 1)
    Process::exit(class_name + " : not needed for single-phase flow!");
 
  int n_l = -1;
  for (int n = 0; n < pbm.nb_phases(); n++)
    if (pbm.nom_phase(n).debute_par("liquide")
        && (n_l < 0 || pbm.nom_phase(n).finit_par("continu")))
      n_l = n;
 
  if (n_l < 0)
    Process::exit(class_name + " : liquid phase not found!");
 
  return n_l;
}
 
/*! @brief Computes the upper-triangular pair index for phases (k, l)
 *         with k < l, used to index the sigma table.
 */
inline int sigma_pair_index(int k, int l, int N)
{
  const int lo = std::min(k, l), hi = std::max(k, l);
  return (lo * (N - 1) - (lo - 1) * lo / 2) + (hi - lo - 1);
}
 
/*! @brief Fills a (ne, nb_pairs) table with surface tension values
 *         for all phase pairs.
 */
inline void compute_sigma_table(const Milieu_composite& milc,
                                const DoubleTab& press, const DoubleTab& temp,
                                int ne, int N, DoubleTrav& Sigma_tab)
{
  const int Np = press.line_size();
  for (int k = 0; k < N; k++)
    for (int l = k + 1; l < N; l++)
      {
        const Interface_base& sat = milc.get_interface(k, l);
        const int idx = sigma_pair_index(k, l, N);
        for (int i = 0; i < ne; i++)
          Sigma_tab(i, idx) = sat.sigma(temp(i, k), press(i, k * (Np > 1)));
      }
}
 
/*! @brief Computes the norm of the relative velocity between phase k
 *         and the liquid phase n_l at element e.
 *         Velocity is a PolyMAC_MPFA face+elem field with element values
 *         stored at offset nf_tot.
 */
inline double relative_velocity_norm(const DoubleTab& vit, int nf_tot, int D,
                                     int e, int k, int n_l)
{
  double u_r_sq = 0.;
  for (int d = 0; d < D; d++)
    {
      const double dv = vit(nf_tot + D * e + d, k) - vit(nf_tot + D * e + d, n_l);
      u_r_sq += dv * dv;
    }
  return std::sqrt(u_r_sq);
}
 
/*! @brief Tomiyama (1998) drag coefficient correlation.
 *         Cd = clamp(16/Re*(1+0.15*Re^0.687), 8*Eo/(3*(Eo+4)), 48/Re)
 *         Returns 0 when u_r == 0 (i.e. Reb == 0).
 */
inline double Tomiyama_Cd(double Reb, double Eo)
{
  if (Reb == 0.)
    return 0.;
  return std::clamp(16. / Reb * (1 + 0.15 * std::pow(Reb, 0.687)),
                    8. * Eo / (3. * (Eo + 4.)),
                    48. / Reb);
}
 
/*! @brief Computes the Eotvos number: Eo = g * |rho_l - rho_k| * d^2 / sigma */
inline double eotvos_number(double g, double rho_l, double rho_k, double d_k, double sigma)
{
  return g * std::abs(rho_l - rho_k) * d_k * d_k / sigma;
}
 
#endif /* Sources_helpers_Multiphase_included */