Examples of data settings for source terms with scalar in a channel

Additional right-hand side source terms for scalar equations (user scalars and specific physics scalars) with the cs_user_source_terms user-defined function.

Local variables and initialization

  /* field structure */
  const cs_field_t  *f = cs_field(f_id);
 
  /* local number of mesh cells */
  const cs_lnum_t  n_cells = cs_glob_mesh->n_cells;
 
  /* mesh quantities */
  const cs_real_t  *cell_f_vol = cs_glob_mesh_quantities->cell_vol;

Only apply to thermal scalar

  if (f != cs_thermal_model_field())
    return;

Function body

Map required fields

  /* velocity */
  const auto cvar_vel = CS_F_(vel)->get_val_v();

Compute bulk mean velocity

  /* bulk mean velocity (x component) */
  cs_real_t  ubulk = 0;
  for (cs_lnum_t i = 0; i < n_cells; i++)
    ubulk += cvar_vel(i, 0) * cell_f_vol[i];
 
  cs::parall::sum(ubulk);  /* sum across processes if needed */
 
  ubulk /= cs_glob_mesh_quantities->tot_vol;

Compute source terms; we want to impose a total flux of 1 Watt.

  /* Flux x Total surface / (rho Cp) */
  cs_real_t tot_flux = 1.;
 
  for (cs_lnum_t i = 0; i < n_cells; i++) {
    st_imp[i] = 0.;
    st_exp[i] = cell_f_vol[i] * cvar_vel(i, 0) * tot_flux / ubulk;
  }