Granular Flow Lubrication: A Lattice-Based Cellular Automata Modeling Approach

Abstract

Liquid lubricants break down at extreme temperatures and promote stiction in micro/nano-scale environments. Consequently, using flows of solid granular particles as a “dry” lubrication mechanism in sliding contacts was proposed, because of their ability to carry loads and accommodate surface velocities. Granular flows are highly complex flows that in many ways act similar to fluids, yet are difficult to predict because they are not well understood. Granular flows are composed of discrete particles which display fluid and solid lubricant behavior with time. This work describes the usefulness of employing lattice-based cellular automata (CA) as a tool for modeling granular flows in tribological contacts. The granular kinetic lubrication (GKL) continuum modeling approach has been successful at predicting trends gleaned from experiments conducted with granules in a couette shear cell. These results are used as a benchmark for determining the effectiveness of the CA modeling results. While the CA model was constructed entirely from rule-based mathematics, velocity and solid fraction results from the simulations were in good agreement with those from the GKL model benchmark results.