8.6.3 User-Defined Anisotropic Diffusivity

You can specify $\Gamma$ in Equation  8.6-1 on a per-scalar basis, directly, through user-defined functions (UDFs).

To specify a UDF for anisotropic diffusivity on a per-scalar basis, first select a scalar equation (e.g., uds-0) from the User-Defined Scalar Diffusion list in the UDS Diffusion Coefficients dialog box (Figure  8.6.5).

Figure 8.6.5: The UDS Diffusion Coefficients Dialog Box

Then choose user-defined-anisotropic in the drop-down list under Coefficient. The User-Defined Functions dialog box will open allowing you to hook a
DEFINE_ANISOTROPIC_DIFFUSIVITY UDF only if you have previously loaded a compiled UDF library or interpreted a UDF. Otherwise, you will get an error message. More information about user-defined functions can be found in the separate UDF Manual.