Volume and boundary zone definitions

(cs_user_zones.c)

Volume and boundary zones may be defined using the GUI, or through the cs_user_zones (in cs_user_zones.c).

Simple volume zone example

Most zones may be defined in a simple manner using the general selection criteria, such as in the following example:

  {
    cs_volume_zone_define("head_loss_1",
                          "box[4.0, 6.0, -1e6, 2.0, 8.0, 1e6]",
                          CS_VOLUME_ZONE_HEAD_LOSS);
  }

Advanced volume zone example

More complex selections can be done by defining an appropriate selection function. For example, to select cells adjacent to boundary faces belonging to a group named "G3", the following selection function must first be defined:

static void
_g3_boundary_cells(void              *input,
                   const cs_mesh_t   *m,
                   int                location_id,
                   cs_lnum_t         *n_elts,
                   cs_lnum_t        **elt_ids)
{
  CS_UNUSED(input);
  CS_UNUSED(location_id);

  /* Allocate selection list */

  cs_lnum_t n_b_faces = 0;
  cs_lnum_t *b_face_ids = NULL;

  BFT_MALLOC(b_face_ids, m->n_b_faces, cs_lnum_t);

  cs_selector_get_b_face_list("G3", &n_b_faces, b_face_ids);

  char *cell_flag;
  BFT_MALLOC(cell_flag, m->n_cells, char);

  for (cs_lnum_t i = 0; i < m->n_cells; i++)
    cell_flag[i] = 0;

  /* Now that flag is built, test for adjacency */

  for (cs_lnum_t i= 0; i < n_b_faces; i++) {
    cs_lnum_t face_id = b_face_ids[i];
    cs_lnum_t c_id = m->b_face_cells[face_id];
    cell_flag[c_id] = 1;
  }

  /* Now build list from flag */

  cs_lnum_t _n_elts = 0;
  for (cs_lnum_t i = 0; i < m->n_cells; i++) {
    if (cell_flag[i] != 0)
      _n_elts++;
  }

  cs_lnum_t *_elt_ids;
  BFT_MALLOC(_elt_ids, _n_elts, cs_lnum_t);

  _n_elts = 0;
  for (cs_lnum_t i = 0; i < m->n_cells; i++) {
    if (cell_flag[i] != 0) {
      _elt_ids[_n_elts] = i;
      _n_elts++;
    }
  }

  /* Free memory */

  BFT_FREE(b_face_ids);
  BFT_FREE(cell_flag);

  /* Set return values */

  *n_elts = _n_elts;
  *elt_ids = _elt_ids;
}

It can then simply be used in a zone definition:

  {
    char name[128], criteria[128];

    for (int i = 0; i < 3; i++) {

      double s_coords[] = {0, 0, 2.0*i};

      snprintf(name, 127, "source_%d", i);
      snprintf(criteria, 127, "sphere[%f, %f, %f, 0.5]",
               s_coords[0], s_coords[1], s_coords[2]);

      cs_volume_zone_define_by_func("G3_B", _g3_boundary_cells, NULL, 0);
    }
  }

Remarks

If defined as "static", as in this example, an with no function prototype, the selection function must be defined in the same file (i.e. cs_user_zones.c), and appear before the definition of cs_user_zones. If a appropriate selection function is available in another source file, it must have non-static linkage an a function prototype must be provided (usually through an associated .h file).