Nanoscale Effect on Ultrathin Gas Film Lubrication in Hard Disk Drive

Since the current thickness of the gas film between the slider and the disk in Hard Disk Drive is already only one order of magnitude larger than the diameter of gas molecules, the nanoscale effect cannot be neglected any longer. In this paper a nanoscale effect function, Np is proposed by investigating the unidirectional flow of the rarefied gas between two parallel plates, and four kinds of formerly and currently employed lubrication models are modified. The calculated results using the modified Reynolds equations indicate that the nanoscale effect weaken the rarefaction effect to some extent for ultra-thin gas film lubrication.