Directional Dependence of Surface Properties
The Surface-to-Surface Radiation interface in the Heat Transfer module implements the ray shooting method, that enables to set the dependence of the emissivity, of the specular reflectivity and of the specular transmissivity on the incident angle.
The polar and azimuthal angles, θ ∈ [0,π/2] and φ ∈ [−π,π], are defined below:
Figure 4-22: Definition of polar and azimuthal angles.
The implementation supports directional surface properties that can be decomposed as the sum of two expressions. The first is defined as a function of θ and φ only, and the other as independent of θ and φ. The latter may depend on any other model quantity like the temperature, or the spatial coordinates.
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Emissivity
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Transmissivity
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Specular reflectivity
Note that no dependence is defined for the diffuse reflectivity, ρd.