Participating Media Radiation (DOM) Material Properties

Absorption Coefficient

The absorption coefficient is the property of a medium that describes the amount of absorption of thermal radiation per unit path length within the medium (m^-1 ).

This value node (Absorption Coefficient in the preceding screenshot) is activated as soon as the Participating Media Radiation model is selected. For the Multiband spectrum model, values of this property can be specified for each spectral band.

The emission coefficient is equal to the absorption coefficient by Kirchhoff’s law.

Weighted Sum of Gray Gases (WSGG)

The Weighted Sum of Gray Gases node becomes available under Absorption Coefficient node when you have gray radiation as your thermal spectrum specification in a multi-component mixture.

This method calculates radiative properties from local gas species concentrations and local temperatures without you specifying them (see Weighted Sum of Gray Gases Methof (WSGGM)). You specify the path length in the Optical Path Length property.

Weighted Sum of Gray Gases Properties

Optical Path Length

Set the optical path length according to the specific case. Where material properties do not vary over distance, you can use Eqn. (1771) to get an estimate.

Scattering Coefficient

The scattering coefficient is the property of a medium that describes the amount of scattering of thermal radiation per unit path length within the medium [m^-1].

This value node (Scattering Coefficient in the preceding screenshot) is activated as soon as the Participating Media Radiation model is selected. For the Multiband spectrum model, values of this property can be specified for each spectral band.

Refractive Index

Refractive index is the property of a medium that indicates the velocity of light in that medium with respect to the velocity of light in some reference medium or in a vacuum. The "relative refractive index" uses velocity of light in a medium (for example, air) as the reference velocity. The "absolute refractive index" uses the velocity of light in a vacuum as the reference velocity. Simcenter STAR-CCM+ uses absolute refractive indices. Direct consequences of refractive index include enhanced local emission and change in direction when light crosses the boundary between media with different refractive indices. See Refraction, Reflection, and Critical Angle.

This value node (Refractive Index in the preceding screenshot) is activated as soon as the Refraction (Gray) model or Refraction (Multiband) model is selected. For the Multiband spectrum model, values of this property can be specified for each spectral band. With gray radiation, there is a single value to set. With multiband radiation, there is a value for each band. The default value of the index of refraction is 1.0. The index of refraction for the environment is always 1.0. Since refractive index in Simcenter STAR-CCM+ is always absolute refractive index, the value is strictly > 1.0.