RADIATION

Specifies global radiation algorithms and parameters.

Type

AcuSolve Command

Syntax

RADIATION {parameters}

Qualifier

This command has no qualifier.

Parameters

view_factor_type (enumerated) [=hemicube]
Calculation method for the view factor.
hemicube
Hemicube. Requires num_hemicube_bins and max_surface_subdivision.
num_hemicube_bins or bins (integer) >0 [=200]
Number of bins for the view factor calculation. Used with hemicube view factor type.
max_surface_subdivision (integer) >=1 [=1]
Maximum number of segments to split a surface facet when proximity condition is violated. Used with hemicube view factor type.
smoothing_type (enumerated) [=least_squares]
Type of view factor smoothing algorithm.
least_squares
Least squares smoothing.
stefan_boltzmann_constant (real) >0 [=5.67e-8]
Stefan-Boltzmann constant. Default is in MKS units.
num_symmetry_planes (integer) >=0 <=3 [=0]
Number of orthogonal symmetry planes in geometrical model.
symmetry_center or center (array) [={0,0,0}]
Any point that lies at the intersection of all symmetry planes. Used with num_symmetry_planes>0.
symmetry_direction_1 (array) [={1,0,0}]
Normal direction to first symmetry plane. Used with num_symmetry_planes>0.
symmetry_direction_2 (array) [={0,1,0}]
Normal direction to second symmetry plane. Used with num_symmetry_planes>1.
symmetry_direction_3 (array) [={0,0,1}]
Normal direction to third symmetry plane. Used with num_symmetry_planes=3.

Description

This command specifies the global parameters for enclosure radiation heat transfer as defined by the RADIATION_SURFACE and EMISSIVITY_MODEL commands. Radiation commands with default values are automatically created for the P1 radiation method to model radiative heat transfer in a grey, optically thick participating medium. These parameters do not apply to radiation boundary conditions defined by ELEMENT_BOUNDARY_CONDITION commands or to heat fluxes defined by SOLAR_RADIATION and related commands.

For example,
EQUATION {
   ...
   radiation                        = enclosure
   absolute_temperature_offset      = 273.14
}
RADIATION {
   view_factor_type                 = hemicube
   num_hemicube_bins                = 200
   max_surface_subdivision          = 4
   smoothing_type                   = least_squares
   stefan_boltzmann_constant        = 5.67e-08
   num_symmetry_planes              = 1
   symmetry_center                  = { 0, 0, 0 }
   symmetry_direction_1             = { 1, 0, 0 }
}

specifies that the enclosure radiation equation is to be solved, the hemicube algorithm with 200 bins per side is used to calculate the view factor, each radiation facet may be split into a maximum of 4 sub-surfaces to reduce proximity and visibility errors, the least squares method is used to smooth the view factor, the Stefan-Boltzmann constant is 5.67x10-, and one symmetry plane is modeled.