AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Effect of Particle Rotation on the Drift Velocity for Non-Spherical Aerosol Particles
GEORGE MULHOLLAND, Charles Hagwood, Mingdong Li, Michael Zachariah, University of Maryland
Abstract Number: 101 Working Group: Aerosol Physics
Abstract The drift velocity of a randomly oriented non-spherical aerosol particle in an external field has been previously computed both in the limit of slow rotation and in the limit of fast rotation but not in the intermediate interval. The low rotation limit has been widely used for a range of non-spherical particles including sphere doublets, straight chain clusters of spheres, nanorods, prolate and oblate spheroids, and fractal agglomerates. A 1- D model equation containing the particle acceleration and an orientation dependent friction coefficient is proposed to predict the drift velocity between the two limits. This model has the essential physical phenomena without the complications of the 3-D treatment of the combined translation and rotation behavior. The long time average linear drift velocity is computed as a function of the rotation velocity and the aspect ratio parameter. As an example, the drift velocity is computed for the model parameters based on the friction coefficient and the rotational diffusion coefficient for circular cross section nanorods in the free molecular regime. The transition region between the slow and fast rotation limits occurs over the reduced rotation velocity interval of 0.2 to 3.0. Results on the effects of the nanorod dimensions, the accommodation coefficient, and the particle density on deviations from the low rotation velocity limit will be presented. For a momentum accommodation coefficient of 0.9 and a particle density of 1000 kg/m$^3, the largest percent deviation from the low rotation limit is 20 % and the deviation is at most 1 % for nanorods of any length for diameters of 20 nm diameter or larger. The effect of the rotation rate on the translational diffusion coefficient will also be discussed.