Theoretical Modeling of the Vapor Cavitation in Dynamically Loaded Journal Bearings

Abstract

A theoretical investigation is made of the evolution of a vapor bubble for a submerged journal bearing under dynamically loaded conditions. The solution to the Reynolds equation is determined numerically using a control volume method (Elrod algorithm). This method conserves mass throughout the computational domain including the liquid-vapor interface which may or may not be in motion relative to the minimum film line. An ADI (Alternating Direction Implicit) method is used to effect the time march. Excellent agreement was found with the experimental work of Jakobsson and Floberg for stationary cavitation. Predictions of bubble life for nonstationary cavitation compare reasonably well with that measured by Jacobson and Hamrock using high-speed photography. A comparison study was performed to determine some of the consequences of applying a nonconservative theory to a dynamic problem. A complete dynamic cycle of a journal whirling in a circular path was chosen for the basis of comparison. Significant differences were observed in the load components near the end of the cycle. In each case, onset of cavitation was observed followed by bubble growth and subsequent collapse. More complete details of this phenomena are illustrated with the use of perspective graphic plots depicting the associated pressure distribution and region of cavitation with position and motion of the journal within the housing.