Schema_Backward_Differentiation_order_2.cpp

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#include <Schema_Backward_Differentiation_order_2.h>
 
#include <Equation_base.h>
#include <Probleme_base.h>
#include <Probleme_Couple.h>
#include <Milieu_base.h>
#include <Param.h>
 
#include <communications.h>
#include <Matrice_Morse.h>
 
Implemente_instanciable(Schema_Backward_Differentiation_order_2,"Schema_Backward_Differentiation_order_2",Schema_Backward_Differentiation_base);
// XD schema_backward_differentiation_order_2 schema_implicite_base schema_backward_differentiation_order_2 INHERITS_BRACE not_set
// XD attr facsec_max floattant facsec_max OPT Maximum ratio allowed between time step and stability time returned by
// XD_CONT CFL condition. The initial ratio given by facsec keyword is changed during the calculation with the implicit
// XD_CONT scheme but it couldn\'t be higher than facsec_max value.NL2 Warning: Some implicit schemes do not permit high
// XD_CONT facsec_max, example Schema_Adams_Moulton_order_3 needs facsec=facsec_max=1. NL2 Advice:NL2 The calculation
// XD_CONT may start with a facsec specified by the user and increased by the algorithm up to the facsec_max limit. But
// XD_CONT the user can also choose to specify a constant facsec (facsec_max will be set to facsec value then). Faster
// XD_CONT convergence has been seen and depends on the kind of calculation: NL2-Hydraulic only or thermal hydraulic
// XD_CONT with forced convection and low coupling between velocity and temperature (Boussinesq value beta low), facsec
// XD_CONT between 20-30NL2-Thermal hydraulic with forced convection and strong coupling between velocity and
// XD_CONT temperature (Boussinesq value beta high), facsec between 90-100 NL2-Thermohydralic with natural convection,
// XD_CONT facsec around 300NL2 -Conduction only, facsec can be set to a very high value (1e8) as if the scheme was
// XD_CONT unconditionally stableNL2These values can also be used as rule of thumb for initial facsec with a facsec_max
// XD_CONT limit higher.
 
 
 
/*! @brief Simple appel a: Schema_Temps_base::printOn(Sortie& ) Ecrit le schema en temps sur un flot de sortie.
 *
 * @param (Sortie& s) un flot de sortie
 * @return (Sortie&) le flot de sortie modifie
 */
Sortie& Schema_Backward_Differentiation_order_2::printOn(Sortie& s) const
{
  return  Schema_Backward_Differentiation_base::printOn(s);
}
 
 
/*! @brief Lit le schema en temps a partir d'un flot d'entree.
 *
 * Simple appel a: Schema_Temps_base::readOn(Entree& )
 *
 * @param (Entree& s) un flot d'entree
 * @return (Entree&) le flot d'entree modifie
 */
Entree& Schema_Backward_Differentiation_order_2::readOn(Entree& s)
{
  return Schema_Backward_Differentiation_base::readOn(s);
}
 
////////////////////////////////
//                            //
// Caracteristiques du schema //
//                            //
////////////////////////////////
 
 
/*! @brief Renvoie le nombre de valeurs temporelles a conserver.
 *
 * Ici : n-1, n et n+1 donc 3.
 *
 */
int Schema_Backward_Differentiation_order_2::nb_valeurs_temporelles() const
{
  return 4 ;
}
 
int Schema_Backward_Differentiation_order_2::nb_valeurs_passees() const
{
  return 1;
}
 
int Schema_Backward_Differentiation_order_2::nb_pas_dt_seuil() const
{
  return 1;
}
 
/////////////////////////////////////////
//                                     //
// Fin des caracteristiques du schema  //
//                                     //
/////////////////////////////////////////
 
void Schema_Backward_Differentiation_order_2::compute_backward_differentiation_coefficients(double time_step, const DoubleTab& times) const
{
  assert(times.size_array() == 3); //past, present and future times, stored in ascending order inside "times" table
 
  if (backward_differentiation_coefficients_.size_array() != 3)
    {
      backward_differentiation_coefficients_.resize(3,RESIZE_OPTIONS::NOCOPY_NOINIT);
    }
 
  double alpha_0 = time_step/(times[2]-times[0]); // for times[0] which means past time
  double alpha_1 = 1.;                            // for times[1] which means present time
 
  backward_differentiation_coefficients_[2] = 1./(alpha_0+alpha_1);                                                    //for times[2] which means future time
  backward_differentiation_coefficients_[1] = alpha_1*backward_differentiation_coefficients_[2]/(1.-alpha_0/alpha_1); //for times[1] which means present time
  backward_differentiation_coefficients_[0] = alpha_0*backward_differentiation_coefficients_[2]/(1.-alpha_1/alpha_0); //for times[0] which means past time
}