A Simplified THD Model for the Steady State Journal Bearing Under Turbulent Flow

Abstract

Turbulence is an irregular fluid motion in which the various flow properties such as velocity and pressure show random variation with time and position. Because of this randomness the instantaneous value of flow properties has little practical significance and it is the average value of properties that is of interest. In turbulence the number of equations in the system available to characterize the flow remains the same as the laminar case. However, the additional unknown term, Reynolds shear stress, contributed due to mean flow and the turbulent fluctuations makes it difficult to solve purely on theoretical grounds. Thus certain assumptions concerning the character of the flow and experimental data are essential to solve the turbulence problem. The paper concerns the hydrodynamic turbulence motion in the lubrication layer, wherein, the thermo hydrodynamic analysis, the Reynolds and energy equations are decoupled and average value of eddy viscosity is used. Recirculation and mixing of the lubricant at inlet and parabolic distribution of temperature across film at the inlet is included in the analysis. Also, a parabolic distribution of temperature across film at the inlet is taken into account. The energy equation in the cavitation zone is treated with the empirical constants/weight age factors for the conduction and convection terms of heat dissipation. The heat generation in the cavitation zone term is neglected. The viscous sub layer is defined by an empirical equation, and the energy equation is treated separately for the viscous sub layer and turbulent core. The grid size is selected on the basis of the viscous sub layer thickness. The predicted results obtained by using the present model are compared with the experimental results.