Comparative Experimental and Numerical Analysis of Flow and Pressure Fields Inside Deep and Shallow Pockets for a Hydrostatic Bearing

Abstract

This article presents the experimental and numerical study of the development of flow patterns and pressure profiles inside a rectangular pocket of a hydrostatic journal bearing where its depth is the main varying parameter. Other parameters are the pocket's aspect ratio, restrictor inlet conditions, and shaft velocity. The flow visualization procedure used a full-flow field tracking method, a Lagrangian method used to follow microsphere particles injected in the flow stream and, through them, visually reconstruct the flow pattern in the pocket. A high-intensity pulsed YAG laser combined with an optical train of lenses was used to create a thin sheet of light that illuminates the particles contained in its plane. A long-distance microscope (LDM) coupled with a video camera digitally recorded the particles’ positions, thus creating instantaneous representative images of the flow structure. The experimental results presented herein are accompanied by a numerical simulation that uses CFD-ACE+, a commercial software package (ESI Group, Hunstville, Ala, 2006). The computational engine employed the full three-dimensional Navier-Stokes equations to simulate the steady-state flow in a hydrostatic pocket when an incompressible Newtonian fluid with constant properties was used. The numerical results display velocity vectors and streamline maps as well as the pressure patterns in both the shallow- and deep-type pockets. These results are then qualitatively compared with the experimental flow patterns acquired for the same type of pockets.