Oscillating circular squeeze films considering the combined effects of fluid inertial forces and non-Newtonian couple stresses

Abstract

Based on the microcontinuum theory, the combined effects of fluid inertial forces and non-Newtonian properties on the oscillating squeeze films of parallel circular discs are investigated theoretically. By applying the momentum approximation method, the pressure-gradient lubrication equation is derived from Stokes couple-stress momentum equations including total fluid inertial terms to account for the non-Newtonian effects arising from a Newtonian base fluid blended with various sorts of additives. A closed-form solution for the oscillating squeeze-film characteristics is then obtained. From the results presented, the combined effects of fluid inertial forces and non-Newtonian couple stresses are characterized by both the squeezing Reynolds number and the couple-stress parameter depending on the amplitude of oscillation. Comparing with the non-inertia Newtonian-lubricant case, the effects of inertial forces (Re=18) provide an increase in the fluid film force to ∼52 per cent for the non-dimensional oscillating amplitude A*=0.3 at the time instant t*=1.7453. Using non-Newtonian fluids as lubricants, the combined effects of fluid inertial forces (Re=18) and non-Newtonian couple stresses (L=0.1) further increase the fluid film force up to ∼86 per cent when compared with the non-inertia Newtonian-lubricant case.