Lubrication Considering Boundary Slip

Synonyms

Lubrication with hydrophobic/lyophobic/oleophobic surfaces; Lubrication with nonwetting/half-wetted surfaces

Definitions

Fluid film lubrication occurs when opposing bearing surfaces are completely separated by a lubricant film.

Boundary lubrication is governed by the physical and chemical properties of thin surface films of molecular proportion.

Scientific Fundamentals

Slip of liquid lubricants on a stationary bearing surface was first considered by Navier in 1823 (Tropea et al. 2007) and dedicated to both type of lubrication regimes gives the possibility of improving the load-carrying capacity.

Mechanism

Accepting the classical assumption of lubrication – constant pressure across the film, Newtonian liquid in laminar and isothermal/isoviscous flow – the momentum equation in dimensionless form reduces for a one-dimensional flow to

$$ \frac{{{{{\rm d}}^2}\bar{u}}}{{{\rm d}{{{\bar{z}}}^2}}} = \frac{{{\rm d}\bar{p}}}{{{\rm d}\bar{x}}} $$

(1)

where $\bar{u} = u/U$; \( \bar{x}...