Abstract View
Effect of Brownian Rotation on the Drift Velocity of a Nanorod
GEORGE MULHOLLAND, Charles Hagwood, National Institute of Standards and Technology, Gaithersburg
Abstract Number: 223
Working Group: Aerosol Physics
Abstract
A model set of equations including Brownian rotation dynamics is proposed to investigate the role of rotation on the drift velocity of nanorods in the direction of the external field (electrical, gravitational). The rotation dynamics is based on the Ornstein - Uhlenbeck type analysis for the calculation of the mean and variance of the rotation velocity and angle for a freely rotating nanorod which includes inertial effects (high frequency). The average drift velocity is computed from the spatial trajectory for each path and the ensemble average and confidence interval is computed from the average of 300 trajectories. The two time scales in the problem, rotation and translation, require a large number of time steps to resolve both motions. Calculations are carried out for a ratio of the time scales, α, ranging from 0.01 to 100. It is shown that in the limit of slow and fast rotation, the velocity approaches the values predicted based on previous studies. The simulations were validated by comparison with the analytic expressions for the rotational model and for the approach to the slow and fast rotation limit within 0.5 %. The value of α is found to be near unity based on kinetic theory calculation of the friction and rotation resistances. This value is closer to the fast rotation limit than the widely used slow rotation limit. Results are also presented for nanodisks and slender rods in the continuum limit.