Drag on a small sphere moving through a gas

Abstract

An approximate theoretical solution is presented for the drag force on a small sphere moving through a gas. The result is based on a moment solution to the Boltzmann equation which places no restriction on the Knudsen number. The equation which is obtained for the drag force reduces to the exact solution in the case of both large and small Knudsen number and gives excellent agreement with experimental data. Copyright © 1975 American Institute of Physics.