Study on Micro-Scale Gas Slider Bearing w ith Direct Simulation Monte Carlo Method

Abstract

MEMS devices with oscillatory or rotating parts need lubrication to achieve long service life. Micro-scale gas-lubricated thrust bearings are investigated by using both MGL and DSMC methods in this paper. As dimensions of the flow field decrease down to micro-scale or nano-scale, the continuum gas flow theory will be invalid. DSMC is a molecule-based method suitable for analyzing micro-scale gas flow or dilute gas dynamics problems. Most of the previous studies in the field was aiming at gas slider bearing between the read/write head and rotating disk in HDD. Only the simple inclined plane slider bearing was studied with the DSMC method for checking the validity of MGL method at nano-scale bearing gap size. In this paper, slider bearings with one and two bumpss are considered. The gas pressure distributions are obtained with the DSMC and compared with the results of MGL simulations. In order to reveal the flow field of slider bearings, stream-wise velocity profiles at different locations are presented. The calculation results indicate that negative slip velocity can be observed near the upper wall of slider bearing when the h1/h0 ratio reaches to 6. It may be the cause of difference in pressure distributions between the results of MGL and DSMC methods.