Effects of an Accommodation Coefficient on the Stresses at the Surface of Slider Gas Bearings with Nano-Meter Spacings : An Analysis Method for Shear Stress and Comparisons with the DSMC Results

Abstract

This paper clarified the effects of accommodation coefficient, which characterize the gas surface scattering at the boundary surfaces, on molecular gas film lubrication charcteristics by the use of the molecular gas film lubrication (MGL) theory and the Direct Simulations Monte Carlo (DSMC) technique. Using the MGL theory, flow rate coefficient Q_P in the MGL equation and shear stress coefficient W_C in Kang's formula, which reflect molecular gas effects, are rigorously calculated with accommodation coefficient α and inverse Knudsen number D as a parameters. An inverse step-type slider with nano-meter spacings was analyzed by the use of these coefficients, and the lubrication characteristics especially normal pressures and shearing stresses are compared with each simulation method. It is found that pressures and shearing stresses by the two methods are in good agreement with each accommodation coefficient. This means that MGL theory and these coefficients we calculated will be correct.