Analysis of ultra-thin gas film lubrication based on the linearized Boltzmann equation. Influence of accommodation coefficient.

Abstract

A generalize Reynolds-type lubrication equation valid for both arbitrary Knudsen numbers, defined as the ratio of the molecular mean free path to the film thickness, and arbitrary accommodation coefficients at boundaries, is derived form a linearized Boltzmann equation. Numerical analyses of lubrication characteristics through the equation for high Knudsen numbers reveal that, if the accommodation coefficient is less than 1, that is, if not all the molecules reflect diffusely as is the case with real gases, load carrying capacities are smaller than those for diffuse reflection.