Multiscale hydrodynamics in line contacts

Abstract

When the continuum fluid film thickness is comparable with the thickness of the physical adsorbed layer on the solid surface in a line contact, the boundary adsorbed layer will play an important effect. The present paper presents a multiscale analysis for this hydrodynamics incorporating both the adsorbed layer effect and the continuum fluid hydrodynamic effect. The adsorbed layer flow is described by the nanoscale flow equation; The flow of the intermediate continuum fluid is described by the special flow equation which shows the coupled effect of the adsorbed layer and the continuum fluid. For a strong fluid-contact surface interaction, the calculation results show that for a small value of the compound curvature radius R of the contact surfaces such as on the scales of 0.01 mm and 0.1 mm, the adsorbed layer effect significantly increases the lubricating film thickness in the contact center in a practically wide dimensionless rolling speed range, while for the value of R on the scale of 1 mm, such an adsorbed layer effect is significant only for a low dimensionless rolling speed, however for the value of R on the scale of 10 mm or more, the adsorbed layer effect is largely reduced for a practical dimensionless rolling speed.