Effect of surface roughness on couple stress squeeze film lubrication of long porous partial journal bearings

Purpose - The aim of this paper is to investigate the effect of surface roughness on the squeeze film characteristics of long porous partial journal bearings with couple stress fluids as lubricant. Design/methodology/approach - The Stokes couple stress fluid model is included to account for the additives effects of lubricant. The Christensen's stochastic method developed for the hydrodynamic lubrication of rough surfaces is used to derive the stochastic Reynolds type equation accounting for the surface roughness and couple stresses, In the context of Christensen's stochastic theory for the hydrodynamic lubrication of rough surfaces, two types of one-dimensional surface roughness (longitudinal and transverse) patterns are considered. The non-linear first order differential equation governing the journal center movement is solved numerically by using the fourth order R-K method. Findings - From the numerical computations of the results, it is found that, the effect of couple stresses is to increase the load carrying capacity and also the response time. The effect of surface roughness is to increase (decrease) the load carrying capacity and the response time for transverse (longitudinal) roughness pattern. However, the effect of permeability parameter is to decrease the load carrying capacity and also to decrease the response time as compared to the solid case. Originality/value - The original findings on the combined effects of surface roughness and couple stresses on the squeeze film characteristics of long porous partial journal bearing are of use to the bearing designers.