A New Cavitation Model for the Simulation of Piston-Ring Lubrication

Abstract

The only strictly conservative cavitation model in hydrodynamic lubrication, is the Elrod–Adams model. In this model, the so called JFO conditions (due to Jacobson & Floberg and Olsson) are
imposed at the cavitation boundary which is an unknown of the problem. Unfortunately, this lubrication model is not well–suited for the simulation of cavitated regions in which the fluid film is attached to just one of the participating surfaces, as happens in piston–ring assemblies. In these regions, the Elrod-Adams model yields a lubricant transport velocity that is half of the physically-realistic value. This has been known for about three decades, but attempts at correcting the numerical models so as to increase the transport velocity have up to now failed. In this communication we first show the reasons for these attempts to have failed, which come from a loss of uniqueness of the associated exact mathematical problem. Then, we introduce a variant of the Elrod–Adams model that has a unique solution while still allowing for the transport velocity in the cavitated region to be adjusted at physically realistic values.
Finally, a first numerical implementation of this new model is discussed, together with test–case results.