### 10.8.7. Scattering Model

The radiative transfer equation includes two terms due to scattering: attenuation by scattering or out-scattering and augmentation by scattering or in-scattering.

In CFX, the scattering term can be controlled independently in several ways. When using the Monte Carlo radiation model, you can optionally specify a scattering model. If you are using an option other than None, you must specify a Scattering Coefficient on the Material Properties form. If you specify a Scattering Coefficient, this does not automatically imply that a scattering model will be used, you must also select either the Gray or Linear Anisotropy models. For details, see Material Details View: Pure Substance in the CFX-Pre User's Guide.

#### 10.8.7.1. Option = None

The scattering coefficient is ignored, even if a non-zero coefficient has been set for the medium. This option could be used, for example, for cases with clean participating gases, without particles, where the absorption coefficient is much larger than the scattering coefficient.

#### 10.8.7.2. Option = Isotropic

It assumes that in-scattering is uniform in all directions.

#### 10.8.7.3. Option = Linear Anisotropy

CFX includes support for the linear anisotropic phase function

| (10–4)

The anisotropy coefficient must be supplied. If the coefficient has spectral dependency, it can be evaluated using CEL expressions using any of the spectral variables: `frequency`, `wavelength`, or `wavenumber`. By default, the coefficient is set to zero.

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