If this node is selected from the Pairs menu, choose the pair to apply this condition to. A pair must 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
External 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 External radiation intensity is
User defined, set a value or expression for
Iext.
Alternatively, choose Blackbody radiation or
Graybody radiation to define
Ii as
Ib(Text) or
εIb(Text), respectively (available with the Radiation in Participating Media interface only). Set the
External temperature Text (SI unit: K, default value 293.15 K) to specify the temperature at which the blackbody radiation intensity
Ib is evaluated
. Alternatively, select an
Ambient temperature defined in an
Ambient Properties node under
Definitions. For
Graybody radiation, the
Emissivity ε and
External Temperature Text should be defined. If the
Emissivity 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
Emissivity, enter another value for
ε. If the
Define properties on each side check box is selected, define the
Emissivity, upside εu and the
Emissivity, downside εd. Select the
Boundary material, upside and
Boundary material, downside to have different material properties on each side. The boundary material specified is used only when
Emissivity, upside or
Emissivity, downside are
From material.
If Wavelength dependence of radiative properties is
Solar and ambient or
Multiple spectral bands, the
External 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 External 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(Text)
, the fractional emissive power for each spectral band at external temperature
FEPk(Text), the emissivity
εk and the
External temperature Text (SI unit: K, default value 293.15 K). For
Graybody radiation, the
Emissivity εk and
External Temperature Text should be defined from a user expression or by selecting an
Ambient temperature defined in an
Ambient Properties node under
Definitions. 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 assumed to be independent of wavelength. If the
Define properties on each side check box is selected, define the
Emissivity, upside εu and the
Emissivity, downside εd. Select the
Boundary material, upside and
Boundary material, downside to have different material properties on each side. The boundary material specified is used only when
Emissivity, upside or
Emissivity, downside are
From material.
If External radiation intensity is
User defined for each band, set a value or expression for
Iext,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 External radiation intensity is
User defined distribution, set a value or expression for
Iλ,ext. 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,ext,u and
Iλ,ext,d.
