Direct verification of the lubrication force on a sphere travelling through a viscous film upon approach to a solid wall
Type
ArticleKAUST Department
High-Speed Fluids Imaging LaboratoryMechanical Engineering Program
Physical Science and Engineering (PSE) Division
Date
2010-05-21Online Publication Date
2010-05-21Print Publication Date
2010-07Permanent link to this record
http://hdl.handle.net/10754/561535
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Experiments were performed to observe the motion of a solid sphere approaching a solid wall through a thin layer of a viscous liquid. We focus mainly on cases where the ratio of the film thickness, ℘, to the sphere diameter, D, is in the range 0.03 ℘</D < 0.09 and the Stokes number, St, a measure of the sphere inertia to viscous forces, is below a critical level Stc so that the spheres do not rebound and escape from the liquid layer. This provides us with the scope to verify the force acting on the sphere, derived from lubrication theory. Using high-speed video imaging we show, for the first time, that the equations of motion based on the lubrication approximation correctly describe the deceleration of the sphere when St < Stc. Furthermore, we show that the penetration depth at which the sphere motion is first arrested by the viscous force, which decreases with increasing Stokes number, matches well with theoretical predictions. An example for a shear-thinning liquid is also presented, showing that this simple set-up may be used to deduce the short-time dynamical behaviour of non-Newtonian liquids. © 2010 Cambridge University Press.Citation
MARSTON, J. O., YONG, W., & THORODDSEN, S. T. (2010). Direct verification of the lubrication force on a sphere travelling through a viscous film upon approach to a solid wall. Journal of Fluid Mechanics, 655, 515–526. doi:10.1017/s0022112010001266Publisher
Cambridge University Press (CUP)Journal
Journal of Fluid Mechanicsae974a485f413a2113503eed53cd6c53
10.1017/S0022112010001266