The entrainment of lubricant at the entrance of a lubrication zone, such as that of a partially starved slider bearing, is analyzed in a closed system using the method of matched asymptotic expansions. A sphere falling together with a small lens of lubricant in a closely fitting tube is shown to fall under gravity at a speed
$V=(Mg−Fc)√[(RC−RS)/RC]/(16π2μRC)$
, where M denotes the total mass of the system, sphere plus lubricant, g the acceleration of gravity, Fc the differential contact force, μ the viscosity of the lubricant, and RC and RS the radii of the tube and the sphere, respectively. Potential biological applications and experimental verification are discussed.
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