Advanced examples

Local variables common to following examples

The following declaration and initialization block is required used for the examples of this section:

  const int n_fields = cs_field_n_fields();
 
  /* Example of specific boundary conditions fully defined by the user,
   * on the basis of wall conditions.
   *
   * We prescribe for zone 'wall_s' a wall, with in addition:
   *   - a Dirichlet condition on velocity (sliding wall with no-slip condition)
   *   - a Dirichlet condition on the first scalar. */
 
  cs_field_t *scal = cs_field("scalar1");

Initialization and finalization

Initialization and finalization is similar to that of the base examples

Example 1

Example of specific boundary conditions fully defined by the user, on the basis of wall conditions selection (mass flow computation, specific logging, ...)

²We prescribe for zone 'wall_s' a wall, with in addition:

• a Dirichlet condition on velocity (sliding wall with no-slip condition)
• a Dirichlet condition on the first scalar.

  {
    const cs_zone_t *zn = cs_boundary_zone_by_name("wall_s");
 
    const cs_lnum_t n_elts = zn->n_elts;
    const cs_lnum_t *elt_ids = zn->elt_ids;
 
    int *vel_icodcl = CS_F_(vel)->bc_coeffs->icodcl;
    auto vel_val_ext = CS_F_(vel)->bc_coeffs->get_val_ext_v();
    auto vel_h_ext = CS_F_(vel)->bc_coeffs->get_h_ext_v();
    auto vel_q_ext = CS_F_(vel)->bc_coeffs->get_q_ext_v();
 
    int *scal_icodcl = scal->bc_coeffs->icodcl;
    auto scal_val_ext = scal->bc_coeffs->get_val_ext();
    auto scal_h_ext = scal->bc_coeffs->get_h_ext();
    auto scal_q_ext = scal->bc_coeffs->get_q_ext();
 
    for (cs_lnum_t elt_idx = 0; elt_idx < n_elts; elt_idx++) {
 
      const cs_lnum_t face_id = elt_ids[elt_idx];
 
      bc_type[face_id] = CS_SMOOTHWALL;
 
      scal_icodcl[face_id] = CS_BC_DIRICHLET;
      vel_icodcl[face_id] = CS_BC_DIRICHLET;
 
      /* Dirichlet value */
 
      scal_val_ext[face_id] = 10.;
 
      vel_val_ext(face_id, 0) = 1.;
      vel_val_ext(face_id, 1) = 0.;
      vel_val_ext(face_id, 2) = 0.;
 
      /* No exchange coefficient */
 
      scal_h_ext[face_id] = cs_math_infinite_r;
 
      vel_h_ext(face_id, 0) = cs_math_infinite_r;
      vel_h_ext(face_id, 1) = cs_math_infinite_r;
      vel_h_ext(face_id, 2) = cs_math_infinite_r;
 
      /* Flux density at 0 */
 
      scal_q_ext[face_id] = 0;
 
      vel_q_ext(face_id, 0) = 0;
      vel_q_ext(face_id, 1) = 0;
      vel_q_ext(face_id, 1) = 0;
    }
  }

Example 2

Example of specific boundary conditions fully defined by the user, with no definition of a specific type.

We prescribe at zone 'surf_h' a homogeneous Neumann condition for all variables.

 
  {
    const cs_zone_t *zn = cs_boundary_zone_by_name("surf_h");
 
    const cs_lnum_t n_elts = zn->n_elts;
    const cs_lnum_t *elt_ids = zn->elt_ids;
 
    /* CAUTION: the value of bc_type must be assigned to CS_UNDEF */
    for (cs_lnum_t elt_idx = 0; elt_idx < n_elts; elt_idx++) {
      const cs_lnum_t face_id = elt_ids[elt_idx];
      bc_type[face_id] = CS_UNDEF;
    }
 
    for (int f_id = 0; f_id < n_fields; f_id++) {
 
      cs_field_t *f = cs_field(f_id);
      if (!(f->type & CS_FIELD_VARIABLE))
        continue;
 
      int *icodcl = f->bc_coeffs->icodcl;
      auto val_ext = f->bc_coeffs->get_val_ext_2d();
      auto h_ext = f->bc_coeffs->get_h_ext_2d();
      auto q_ext = f->bc_coeffs->get_q_ext_2d();
 
      for (cs_lnum_t elt_idx = 0; elt_idx < n_elts; elt_idx++) {
        const cs_lnum_t face_id = elt_ids[elt_idx];
 
        icodcl[face_id] = CS_BC_NEUMANN;
        for (cs_lnum_t ii = 0; ii < f->dim; ii++) {
          val_ext(face_id, ii) = 0.;
          h_ext(face_id, ii) = cs_math_infinite_r;
          q_ext(face_id, ii) = 0.;
        }
      }
    }
  }

Example 3

Example of wall boundary condition with automatic continuous switch between rough and smooth.

  {
    const cs_zone_t *zn = cs_boundary_zone_by_name("r_wall");
 
    const cs_lnum_t n_elts = zn->n_elts;
    const cs_lnum_t *elt_ids = zn->elt_ids;
 
    if (cs_field_try("boundary_roughness") != nullptr) {
 
      auto bpro_roughness = cs_field("boundary_roughness")->get_val_s();
 
      for (cs_lnum_t elt_idx = 0; elt_idx < n_elts; elt_idx++) {
 
        const cs_lnum_t face_id = elt_ids[elt_idx];
 
        bc_type[face_id] = CS_SMOOTHWALL;
 
        /* Boundary roughtness (in meter) */
        bpro_roughness[face_id] = 0.05;
      }
    }
  }