LUBRICATING MOTION OF A SPHERE IN A CONICAL VESSEL

The final stage of sedimentation of a spherical particle moving along the axis of a conical vessel containing a viscous incompressible fluid is studied both theoretically by lubrication analysis and experimenta lly by laser interferometry. The particle settling velocity varies lik e d(5/2), when d is the gap. There is an excellent agreement between t his result from lubrication theory and experiment, the upper bound bei ng for a gap of about 1/30 radius and the lower practical bound being at the size of the particle roughness. (C) 1998 American Institute of Physics.