The hydraulic conductance of a capillary with a sinusoidally varying cross-section

Using lattice‐gas cellular automata we simulated fluid flow through a straight tube with a sinusoidally varying cross‐section, i.e., what we call a varicose tube. We found that the hydraulic conductance of such a constricted tube was bounded between the long‐wavelength values predicted by Reynolds' equation and the so‐called “stagnant limit” at short wavelengths. In particular, we conclude that pore space associated with roughness at wavelengths shorter than about 15% of the pore radius, should not contribute to hydraulic conductivity and need not be resolved for flow simulation purposes.