Impact of the cavitation model on the theoretical performance of heterogeneous slip/no-slip engineered contacts in hydrodynamic conditions

Abstract

Today's industry faces intense pressure to reduce energy consumption and to extend components' lifetimes in order to reduce economic and environmental costs. During the last few years, it has been pointed out that fluid wall slip is likely to improve friction in low-loaded mechanisms; if the slip zone covers only a specific zone of the surface, improvement of both load and friction can be obtained. The physico-chemical heterogeneity of the surface acts as a geometrical discontinuity and induces pressure gradients analogous to those occurring in a Rayleigh step bearing. Such favourable behaviour can be inhibited if the location of the slip/no-slip areas causes cavitation. This article aims to show the importance of the choice of the cavitation model in the analysis of slip/no-slip hydrodynamic contacts. Current practice predicts the performance of cavitated devices by using the well-known Half-Sommerfeld or Swift—Stieber models. However, using a mass-flow conserving model such as the so-called Floberg—Elrod—Adams model can lead to qualitatively and quantitatively different conclusions. The simple case of a parallel slider bearing is of particular interest. If alternating slip/no-slip areas are introduced, then a non-zero load-carrying capacity can be obtained whose theoretical value dramatically depends on the cavitation model and even on the inlet flowrate of the lubricant.