Effect of Roughness of Confining Surface on Diffusive Motion of Fluid

We propose a model to study self-diffusion of fluid confined between two rough walls. The model is based on microscopic considerations wherein the configuration space of the body systems is divided into cells. Within the cell, it executes harmonic motion unless it finds a saddle point on potential energy hypersurface. Results are obtained for Lennard Jones fluid for different order of rectangular and sinusoidal roughness of confining walls. It is found that the roughness of wall significantly affects the motion of fluid and reduces the average diffusion of particles in agreement with simulation results. The reduction is more for rectangular than for sinusoidal roughness. The study has applicability for fluids flowing in biological systems.