Use the Bosanquet Approximation command to approximate the diffusivity for intermediate Knudsen numbers. You must compute the Knudsen diffusion and the Bulk (Laplace) Diffusion before you can apply this command.

This command uses the relative diffusivity at (computed with the Bulk Diffusion command) and (computed with the Knudsen diffusion command) as input. These input parameters describe the geometry of the 3D structure. With this input, Bosanquet's formula allows to estimate the dimensional effective diffusivity for any gas species at arbitrary Knudsen numbers.

Be aware that the result is a quick approximation, and the specific diffusion process is not simulated. To model the specific process, you can use the Molecular Diffusion command.