Frictional Force on a Small Spherical Particle under Sedimentation to a Plane Plate

Abstract

The flow field of a gas around a spherical particle moving slowly toward a plane plate is analyzed by taking the surface slip of the gas into account, and the stream lines around the particle at some given distances from the plate are illustrated. Frictional forces at arbitrary distances from the plate in the region of Knudsen numbers less than unity are calculated, and dependencies of the frictional force on particle-plate separation distance and on the Knudsen number are made clear. The frictional force increases sharply at any Knudsen number in that region as the particle approaches the plate.