Activation of the module

The module can be activated in the usppmo routine in cs_user_parameters.f90. The corresponding keyword is iirayo in the cs_glob_rad_transfer_params structure.

This member can take the values:

iirayo = 0: module desactivated.
iirayo = 1: the module is activated and the Discrete Ordinates Method is used.
iirayo = 2: the module is activated and the P1 model is used.

Radiation module specific parameters.

When the module is activated, its specific input parameters should be set in the cs_user_radiative_transfer_parameters function of the cs_user_radiative_transfer.c file.

Calculation options for the radiative transfer module.

Radiative transfer parameters may be defined using the cs_user_radiative_transfer_parameters function.

  /* indicate whether the radiation variables should be
     initialized (=0) or read from a restart file (=1) */
  cs_glob_rad_transfer_params->restart = (cs_restart_present()) ? 1 : 0;
  /* period of the radiation module */
  cs_glob_rad_transfer_params->nfreqr = 1;
  /* Quadrature Sn (n(n+2) directions)
     1: S4 (24 directions)
     2: S6 (48 directions)
     3: S8 (80 directions)
     Quadrature Tn (8n^2 directions)
     4: T2 (32 directions)
     5: T4 (128 directions)
     6: Tn (8*ndirec^2 directions)
  */
  cs_glob_rad_transfer_params->i_quadrature = 4;
  /* Number of directions, only for Tn quadrature */
  cs_glob_rad_transfer_params->ndirec = 3;
  /* Method used to calculate the radiative source term:
     - 0: semi-analytic calculation (required with transparent media)
     - 1: conservative calculation
     - 2: semi-analytic calculation corrected
          in order to be globally conservative
     (If the medium is transparent, the choice has no effect) */
  cs_glob_rad_transfer_params->idiver = 2;
  /* Verbosity level in the log concerning the calculation of
     the wall temperatures (0, 1 or 2) */
  cs_glob_rad_transfer_params->iimpar = 1;
  /* Verbosity mode for the Luminance (0, 1 or 2) */
  cs_glob_rad_transfer_params->iimlum = 0;
  /* Compute the absorption coefficient through Modak (if 1 or 2),
     or do not use Modak (if 0).
     Useful ONLY when gas or coal combustion is activated
     - imodak = 1: ADF model with 8 wave length intervals
     - imodak = 2: ADF model with 50 wave length intervals */
  cs_glob_rad_transfer_params->imodak = 2;
  /* Compute the absorption coefficient via ADF model
     Useful ONLY when coal combustion is activated
     imoadf = 0: switch off the ADF model
     imoadf = 1: switch on the ADF model (with 8 bands ADF08)
     imoadf = 2: switch on the ADF model (with 50 bands ADF50) */
  cs_glob_rad_transfer_params->imoadf = 1;
  /* Compute the absorption coefficient through FSCK model (if 1)
     Useful ONLY when coal combustion is activated
     imfsck = 1: activated
     imfsck = 0: not activated */
  cs_glob_rad_transfer_params->imfsck = 1;
  /* Activate Infra Red absoption for atmospheric flows
       atmo_ir_absorption = true: activated
       atmo_ir_absorption = false: not activated */
  cs_glob_rad_transfer_params->atmo_ir_absorption = true;

Radiative transfer boundary conditions

Sketch of thermal flux in boundary walls

The radiative boundary condition is based on the calculation of a new wall temperature. This temperature is computed with a thermal flux balance:

${ Q_{conduction} = Q_{convection} + (Q_{rayt_{absorption}} - Q_{rayt_{emission}}})$

Therefore :

$\dfrac{xlamp}{epap} (T_{fluid} - T_{wall}) = h_{fluid} (T_{fluid} - T_{wall}) + epsp (Q_{incid} - \sigma * T_{wall})$

Note: In Code_Saturne the flux is positive when it is oriented from inside to outside.

Body	Emissivity
polished steel	0.06
oxidized steel	0.80
steel rough	0.94
polished aluminium	0.04
oxidiezd aluminium (inside)	0.09
oxidized aluminium (wet air)	0.90
brick	0.93
concrete	0.93
paper	0.8 to 0.9
water	0.96

Boundary faces identification

Boundary faces may be identified using the getfbr function, or preferrably, through boundary zones, defined using the GUI or the cs_user_zones function..

Initialization and finalization

The following declaration and initialization block needs to be added for the following examples:

  cs_real_t tkelvi = cs_physical_constants_celsius_to_kelvin;
  cs_lnum_t n_b_faces = cs_glob_mesh->n_b_faces;
  const cs_zone_t *zone = NULL;
  int *izfrdp = cs_boundary_zone_face_class_id();

Remaining initialisation

ivar: number of the thermal variable

  cs_field_t *fth = cs_thermal_model_field();
  const cs_lnum_t ivart
    = cs_field_get_key_int(fth, cs_field_key_id("variable_id")) - 1;

Min and Max values for the wall temperatures (clipping otherwise)

$T_{min}$ and $T_{max}$ are given in Kelvin.

*tmin = 0.0;

*tmax = cs_math_big_r + tkelvi;

Assign boundary conditions to boundary wall

Zone definitions

For each boundary face face_id, a specific output (logging and postprocessing) zone id may be assigned. This allows realizing balance sheets by treating them separately for each zone. By default, the output zone id is set to the general (input) zone id associated to a face.

To access output zone ids (both for reading and modifying), use the cs_rad_transfer_get_output_b_face_zone_ids function. The zone id values are arbitrarily chosen by the user, but must be positive integers; very high numbers may also lead to higher memory consumption.