Examples of ALE boundary conditions

Mapping relative to ALE

 
  const cs_lnum_t n_b_faces = domain->mesh->n_b_faces;
  const cs_lnum_t *b_face_vtx_idx = domain->mesh->b_face_vtx_idx;
  const cs_lnum_t *b_face_vtx_lst = domain->mesh->b_face_vtx_lst;
  const cs_lnum_t *b_face_cells = domain->mesh->b_face_cells;
 
  const int nt_cur = domain->time_step->nt_cur;
 
  const cs_real_t *dt = CS_F_(dt)->val;
 
  /* nodes displacement */
  cs_real_3_t *disale
    = (cs_real_3_t*)cs_field_by_name("mesh_displacement")->val;
 
  const cs_zone_t  *zn = nullptr;
 

Assign boundary conditions to boundary faces

One may use selection criteria to filter boundary case subsets.
Loop on faces from a subset.
Set the boundary condition for each face.

Calculation of displacement at current time step

Example 1

Example : For boundary faces of color 4 assign a fixed velocity

 
  /* Example: For boundary faces of zone 'fv' assign a fixed velocity */
  zn = cs_boundary_zone_by_name("fv");
 
  cs_field_t *mesh_u = CS_F_(mesh_u);
 
  /* Calculation of displacement at current time step */
  const cs_real_t deltaa = sin(3.141596*(nt_cur-1)/50);
  const cs_real_t delta  = sin(3.141596*nt_cur/50.);
 
  for (cs_lnum_t ilelt = 0; ilelt < zn->n_elts; ilelt++) {
 
    const cs_lnum_t face_id = zn->elt_ids[ilelt];
    const cs_lnum_t c_id = b_face_cells[face_id];
 
    ale_bc_type[face_id] = CS_BOUNDARY_ALE_IMPOSED_VEL;
    mesh_u->bc_coeffs->rcodcl1[n_b_faces*0 + face_id] = 0;
    mesh_u->bc_coeffs->rcodcl1[n_b_faces*1 + face_id] = 0;
    mesh_u->bc_coeffs->rcodcl1[n_b_faces*2 + face_id] = (delta-deltaa)/dt[c_id];
 
  }

Example 2

Example: For boundary face of color 5 assign a fixed displacement on nodes

  zn = cs_boundary_zone_by_name("fd");
 
  for (cs_lnum_t ilelt = 0; ilelt < zn->n_elts; ilelt++) {
 
    const cs_lnum_t face_id = zn->elt_ids[ilelt];
 
    for (cs_lnum_t ii = b_face_vtx_idx[face_id];
         ii < b_face_vtx_idx[face_id+1];
         ii++) {
      const cs_lnum_t vtx_id = b_face_vtx_lst[ii];
      if (impale[vtx_id] == 0) {
        disale[vtx_id][0] = 0;
        disale[vtx_id][1] = 0;
        disale[vtx_id][2] = delta;
        impale[vtx_id] = 1;
      }
    }
  }
 

Example 3

Example : For boundary faces of color 6 assign a sliding boundary

  zn = cs_boundary_zone_by_name("sb");
 
  for (cs_lnum_t ilelt = 0; ilelt < zn->n_elts; ilelt++) {
 
    const cs_lnum_t face_id = zn->elt_ids[ilelt];
 
    ale_bc_type[face_id] = CS_BOUNDARY_ALE_SLIDING;
 
  }

Example 4

Example : Prescribe elsewhere a fixed boundary

 
  zn = cs_boundary_zone_by_name("fixed");
 
  for (cs_lnum_t ilelt = 0; ilelt < zn->n_elts; ilelt++) {
 
    const cs_lnum_t face_id = zn->elt_ids[ilelt];
 
    ale_bc_type[face_id] = CS_BOUNDARY_ALE_FIXED;
 
  }