Modified average Reynolds equation for ultra-thin film gas lubrication considering roughness orientations at arbitrary Knudsen numbers

In this paper, the effects of roughness orientations and molecular mean free path on the roughness-induced flows are discussed. Based on the newly-proposed modified Reynolds equation, the flow factors are derived in compact forms by using the perturbation approach and the coordinate transformation. The flow factors are expressed as functions of surface characteristics (roughness orientation angles, Peklenik numbers and standard deviations of bearing surfaces) and gas rarefraction parameters (inverse Knudsen numbers). In the result, a comparison of several approximations of the rarefied gas models is discussed. Finally, the static performance of a magnetic recording head under ultrathin spacing conditions with roughness and rarefaction effects taken into account is analyzed. (C) 1997 Elsevier Science S.A.