The effect of the accommodation coefficient on slider air bearing simulation

In solving the slider air bearing problem, both the Molecular Gas-film Lubr ication (MGL) model and the Direct Simulation Monte Carlo (DSMC) model requ ire the accommodation coefficient as input. The accommodation coefficient r epresents the fraction of the air molecules that interact with solid bounda ries ii? a diffusive manner In general, the value I is used for the accommo dation coefficient which represents a fully diffusive reflection. However, in magnetic hard disk drives, the disk and slider surfaces are becoming eve r smoother with different kinds of lubrication on the disk, while the tempe rature is becoming higher due to the faster spindle speed. Under these cond itions the unit value of the accommodation coefficient may no longer be sui table. In order to understand the effect of the accommodation coefficient o n the slider's flying parameters, we used Kang's new database far the Poise uille flow rate Q(p) and Couette flow rate Q(c) to solve the modified Reyno lds equation for two groups of sliders, e.g., negative and positive pressur e sliders ("negative" refers to sliders with subambient pressure zones). Th e results show that, in general, the smaller the accommodation coefficient, the lower the flying height and pitch angle. Positive pressure sliders are more sensitive to the accommodation coefficient than are negative pressure sliders. The typical discrepancy in flying height is around 10%. Also, it is shown that for positive pressure sliders the lower the flying height, th e larger the discrepancy percentage. [S0742-4787(00)00402-1].