Knudsen diffusion is typically modeled using the Knudsen number (Kn), which is the ratio of the mean free path of the gas molecules to the characteristic dimension of the confining structure. When Kn is greater than 1, Knudsen diffusion dominates. The flux of gas molecules can be described using the Knudsen diffusion equation:
J = -D_K * (dC/dx)
where J is the flux, D_K is the Knudsen diffusion coefficient, and dC/dx is the concentration gradient.
