An analysis on the influence of oil pocket shape and distribution on the reduction of friction in hydrodynamic lubrication

The efficiency of moving parts of a machine is dependent on the friction losses and resulting wear between mating surfaces. The hydrodynamic lubrication between these surfaces can be improved using surface texturing, which enhances the tribological characteristics of the surface. In this work, the effect of the variation in shape and distribution of micro-pores in hydrodynamic lubrication is studied. A three-dimensional CFD analysis was done on a simplified model of the textured surface to understand its influence on the load carrying capacity and coefficient of friction. Oil pockets consisting of hemispherical and different orientations of the semi-ellipsoidal dimple were used for the simulation. Additionally the variation of the Reynolds number, dimple depth and area density was investigated. It was found that the semi-ellipsoidal dimples with major axis aligned along the lubricant flow direction performed better in terms of load bearing capacity and lower friction. There existed an optimum dimple depth where the coefficient of friction was minimum for both dimple shapes. Further it was observed that an increase of area density of dimples led to a significant decrease in coefficient of friction.