AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Effect of Orientation on the Mobility and Dynamic Shape Factor of Charged Axially Symmetric Particles in an Electric Field
MINGDONG LI, George Mulholland, Michael Zachariah, University of Maryland
Abstract Number: 198 Working Group: Aerosol Physics
Abstract The mobility of a nonspherical particle is a function of both particle shape and orientation. Thus unlike spherical particles the mobility, through its orientation, depends on the magnitude of the electric field. In this work, we develop a general theory, based on an extension of the work of Happel and Brenner (1965), for the orientation-averaged mobility applicable to any axially symmetric particle for which the friction tensor and the polarization energy are known. By using a Boltzmann probability distribution for the orientation, we employ a tensor formulation for computing the orientation average mobility rather than a scalar analysis previously employed by Kim et al (2007) for nanowires. The resulting equation for the average electrical mobility is much simpler than the expression based on the scalar approach, and can be applied to any axially symmetric structures such as rods, ellipsoids and touching spheres. The theory is applied to the specific case of nanowires and the results experimental results on the mobility of carbon nanotubes (CNT). A set of working formulas of additional mobility expressions for nanorods and prolate spheroids in free molecular, continuum and transition regimes are also presented . Finally, we examine the expression of dynamic shape factor common in the literature, and propose a clearer definition based on the tensor approach. Mathematica codes for the electrical mobility evaluations for five prototype cases (section 2.5.1. – section 2.5.5.) are provided in the Supporting Information.