Gap-Dependent Hydrodynamic Lubrication in Conformal Contacts

TL;DR

This paper reveals a universal power-law behavior in hydrodynamic lubrication of conformal contacts, with deviations indicating transitions to other lubrication regimes, supported by analysis of experimental data.

Contribution

It introduces a gap-dependent model predicting a universal S^{2/3} friction scaling in conformal contacts and explains deviations observed in experiments.

Findings

Universal S^{2/3} friction scaling in conformal contacts

Deviations occur when gap drops below texture length scale

Analysis of oral processing data supports the model

Abstract

We show that the hydrodynamic lubrication of contacting conformal surfaces with a typical texture height gives rise to a universal behaviour in the Stribeck curve in which the friction coefficient shows an anomalous power-law dependence on the Sommerfeld number, $\mu \sim S^{2/3}$. When the gap height drops below the `texture length scale', deviations from $S^{2/3}$ occur, which may resemble the onset of elasto-hydrodynamic and mixed lubrication. Within this framework, we analyse literature data for oral processing and find $S^{2/3}$ scaling with deviations consistent with measured lengthscales.