An average Reynolds equation for non-Newtonian fluid with application to the lubrication of the magnetic head-disk interface

A closed form of the average Reynolds equation is derived for non-Newtonian inelastic fluids with roughness effects taken into consideration. The derivation of flow factors is carried out by means of the perturbation approach with Green's function technique. A coordinate transformation is also utilized to make the equation similar with the Newtonian ones. The results of flow factors are expressed as functions of the Peklenik numbers and the standard deviations of roughness heights of each surface, as well as functions of the film thickness ratio and the flow behavior index of the power-law fluid of the lubrication film. One can find a critical value for Peklenik number (gamma(cr)) from the expressions of pressure flow factors. When gamma > gamma(cr) (gamma < gamma(cr)), the pressure flow factors increase as n increases (decreases). A modified Peklenik number is defined to reveal the interactions between roughness orientations and the non-Newtonian flow. Furthermore, an appropriate combination of fluid properties and surface characteristics will introduce a flow with desired roughness effects. Finally, the static performance of near-contact recording in magnetic head disk files is analyzed, and the effect of the flow behavior index of the power-law fluid on load capacity is found more significant than that of the roughness.