Abstract
The effects of surface roughness on the molecular gas lubrication characteristics have been studied for defining the application limit of Molecular gas film lubrication (MGL) equation against roughness. The applicability has been evaluated by comparing the difference of characteristics calculated by MGL equation and direct simulation Monte Carlo (DSMC) method. In this paper, the evaluation for the two kinds of gas film, the one of which has sinusoidal surface roughness and the other has triangular surface roughness, is presented to check the influence of roughness shape. It comes evident that the magnitude of transverse flow velocity has close relationship with the slope of surface roughness, by comparing the flow pattern of two roughness shapes. The transverse flow, which is not included in MGL equation, causes the difference between the results obtained by MGL equation and DSMC methods and, thus, can be the index of applicability of MGL equation. After all, the causality between the transverse flow and the roughness slope is clarified and their influence to the applicability of MGL equation is confirmed.
