Opacity (Surface-to-Surface Radiation interface)
This node enables to define the surface-to-surface radiation direction on boundaries surrounding the domains where it is defined. When several spectral bands are defined, the opacity can be set for all or only a selection of wavelengths.
When the Radiation direction is defined by Opacity controlled in surface-to-surface boundary features (Diffuse Mirror (Surface-to-Surface Radiation interface), Diffuse Surface (Surface-to-Surface Radiation interface), Prescribed Radiosity (Surface-to-Surface Radiation interface), Opaque Surface (Surface-to-Surface Radiation interface)), surface-to-surface radiation propagates in non-opaque domains. Alternatively the Radiation direction can be defined using the normal orientation or on both sides of boundaries. In this case the Opacity node is ignored. Note that on boundaries where the Semi-Transparent Surface (Surface-to-Surface Radiation interface) is applied, the Radiation direction is Both sides, and the Opacity node is ignored.
By default, the exterior of the Surface-to-Surface Radiation interface is considered as transparent. To set it as opaque, change the Selection of the Opacity node to All voids in the Domain Selection section, and set it as Opaque. Depending on the geometry, an infinite void and several finite voids may be available for the selection.
Opacity
Depending on the Wavelength dependence of surface properties defined in the Radiation Settings section of the physics interface settings, different sections display underneath:
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When Wavelength dependence of surface properties is set to Constant, select Opaque or Transparent to set the domain’s opacity type.
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When Wavelength dependence of surface properties is set to Solar and ambient or Multiple spectral bands, set the opacity for each spectral band by selecting the corresponding check box in the Opaque column of the table. By default the check box is selected for all spectral bands.
If this feature is combined with heat transfer in 2D and 1D, the thickness is assumed to be infinite for the view factor computation. The user-defined value for dz is still used in the heat transfer equation.
Free Convection in a Light Bulb: Application Library path Heat_Transfer_Module/Thermal_Radiation/light_bulb
Thermo-Photo-Voltaic Cell: Application Library path Heat_Transfer_Module/Thermal_Radiation/tpv_cell
Location in User Interface
Context menus
Surface-to-Surface Radiation>Opacity
Ribbon
Physics Tab with Surface-to-Surface Radiation selected in the model tree:
Domains>Opacity