Abstract: As the spacing between the flying head/slider and the rotating disk in hard disk drives (HDDs) continues to decrease, the interaction between the molecular gas and the surfaces of the disk and the head/slider becomes significant. The influence of disk velocity and accommodation coefficients (ACs) at slider and disk surfaces are important factors to govern the static characteristics of air bearing films. A simplified molecular gas film lubrication (MGL) equation is solved by using a mesh-less method, called least square finite difference (LSFD) method. Effects of the ACs on static characteristics of the air bearing film in HDDs with different disk velocities and ultra-low flying heights are investigated. Numerical results show that effects of ACs at slider and disk surfaces on the static characteristics are obvious for the case of symmetric molecular interaction. The effects of ACs at the disk surface on the static characteristics are obvious for the case of non-symmetric molecular interaction, while effects of ACs at the slider surface on the static characteristics are weak. The position of the maximum pressure changes uniformly with the increase of the disk velocity or the minimum flying height under different conditions of ACs.

Key words: Accommodation coefficient, Gas bearings film, Hard disk storage, Meshless method, Molecular gas film lubrication equation