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By default, Surface emissivity ε (dimensionless) and Diffuse reflectivity ρd (dimensionless) use values From material. These are properties of the surface that depend both on the material itself and the structure of the surface. Make sure that a material is defined at the boundary level (by default materials are defined at the domain level).
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For User defined, set values or expressions. You can define the emissivity and reflectivity as functions of temperature using the variable rad.T.
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By default, the Surface emissivity ε (dimensionless) and Diffuse reflectivity ρd (dimensionless) use values From material.
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When Surface emissivity is User defined, enter a value or expression for Surface emissivity ε. The wavelength is accessible through the rad.lambda variable. Any expression set for the emissivity is then averaged over each spectral band to obtain a piecewise constant emissivity. If the average value of the emissivity on each band is known, you can use instead the User defined for each band option to avoid the evaluation of the average.
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When Diffuse reflectivity is User defined, enter a value or expression for the Diffuse reflectivity ρd. The wavelength is accessible through the rad.lambda variable. Any expression set for the reflectivity is then averaged on each spectral band to obtain a piecewise constant reflectivity. If the average value of the reflectivity on each band is known, you may use instead the User defined for each band option to avoid the evaluation of the average.
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When Surface emissivity is User defined for each band, enter a value for the Surface emissivity for each spectral band. Within a spectral band, each value is assumed to be independent of wavelength. By default, the same emissivity is set on both sides. Select the Define surface emissivity on each side check box and fill the Upside and Downside columns of the table for a specific definition on each side.
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When Diffuse reflectivity is User defined for each band, enter a value for the Diffuse reflectivity for each spectral band. Within a spectral band, each value is assumed to be independent of wavelength. By default, the same reflectivity is defined on both sides. Select the Define diffuse reflectivity on each side check box and fill the Upside and Downside columns of the table for a specific definition on each side.
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