Effect of Surface Roughness on the Pressure Generation in a Finite Rough Hydrodynamic Journal Bearing under Micropolar Lubrication in Steady-State

In hydrodynamic lubrication of journal bearing pressure of the fluid film is generated as a result of the viscous drag of the fluid into the wedge shaped gap between the journal and bearing due to relative motion of the journal with respect to the bearing. The pressure development of fluid is important in this type of lubrication to ensure performance of journal bearing. On the other hand, every surface has some degree of roughness that affects relative motion of the journal bearing system. This paper, thus, aims to present a detailed study of hydrodynamic pressure built up of a journal bearing including the roughness of the surfaces. The modified Reynolds equation is derived on the basis of theory of micropolar lubrication incorporating suitable roughness model. The resulting equation is solved numerically at steady state operating condition using cavitation boundary condition to observe distribution of pressure. The effects of variations in operating variables in terms of characteristic of lubricant and parameters defining roughness model are computed. The analytical results are compared with the available published results to validate the theory and computer code. The numerical result shows that for same geometrical condition maximum pressure developed in micropolar fluid always remain higher than that in Newtonian fluid. The steady state pressure is found to be decreased as the values of the roughness parameters are increased.