Viscous Resistance of Straight-Chain Aggregates of Uniform Spheres

Abstract

The viscous resistance of a straight-chain aggregate of uniform spheres is of particular interest because it approximates the resistance of a particle shape frequently observed in aerosol systems, namely, a straight-chain aggregate of roughly uniform, roughly spherical particles. Moreover, this nonspherical particle shape is readily generated in the laboratory and used to calibrate aerosol instruments and processes. A method for calculating the viscous resistance is described for such a particle shape, and example results are presented for a broad range of chain lengths and Knudsen numbers. The method employs an interpolation between the continuum resistance and that for free-molecule flow. The results are discussed in connection with the few experimental data available.