If this node is selected from the Pairs menu, choose the pair on which to apply this condition. A pair has to be created first. See
Identity and Contact Pairs in the
COMSOL Multiphysics Reference Manual for more details.
When Wavelength dependence of radiative properties is
Constant, the
Boundary radiation intensity Ii should be specified. This represents the value of radiative intensity along incoming discrete directions. Values of radiative intensity on outgoing discrete directions are not prescribed. If
Boundary radiation intensity is
User defined, set a value or expression for
Iwall. Alternatively, choose
Blackbody radiation or
Graybody radiation to define
Ii as
Ib(T) or
εIb(T), respectively (available with the Radiation in Participating Media interface only)
. For
Graybody radiation, the
Surface emissivity ε should be defined. If it is defined
From material, make sure that a material is defined at the boundary level (materials are defined by default at the domain level). If
User defined is selected for the
Surface emissivity, enter another value for
ε. If the
Define surface emissivity on each side check box is selected, define the
Surface emissivity, upside εu and the
Surface emissivity, downside εd.
If Wavelength dependence of radiative properties is
Solar and ambient or
Multiple spectral bands, the
Boundary radiation intensity Ii,k for each spectral band should be specified. Select an option between
Graybody radiation,
Blackbody radiation,
User defined for each band, or
User defined distribution.
If Boundary radiation intensity is
Blackbody radiation or
Graybody radiation (available with the Radiation in Participating Media interface only),
Ii,k is defined from the blackbody intensity
Ib(T), the fractional emissive power for each spectral band,
FEPk, and the emissivity,
εk. For
Graybody radiation, the
Surface emissivity εk should be defined. For
User defined for each band, set a value for each spectral band in the table displayed underneath. Within a spectral band, each value is supposed to be wavelength-independent. If the
Define surface emissivity on each side check box is selected, define the
Surface emissivity, upside εu and the
Surface emissivity, downside εd.
If Boundary radiation intensity is
User defined for each band, set a value or expression for
Iwall,k for each spectral band in the table displayed underneath. If the
Define incident intensity on each side check box is selected, set values in the
Upside and
Downside columns.
If Boundary radiation intensity is
User defined distribution, set a value or expression for
Iλ,wall. Any expression is then averaged on each spectral band to obtain a piecewise constant radiation intensity. If the average value of the radiation intensity on each band is known, you may use instead the
User defined for each band option to avoid the evaluation of the average. If the
Define incident intensity on each side check box is selected, set values for
Iλ,wall,u and
Iλ,wall,d.
