The creeping motion of an aerosol aggregate composed of two touching spheres is investigated. A continuum-slip theory, suitable for small values of Knudsen number, is developed. The drag on a pair of equal spheres moving along their line of centers is determined. For vanishing Knudsen number, this drag reduces to Faxe´n’s result. Theoretical results for the effect of small Knudsen number are compared with an approximate expression based on calculations for separated spheres.

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