AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Experimental Observation of Ballistic to Brownian Transition in an Aerosol System
PAI LIU, William Heinson, Rajan Chakrabarty, Washington University in St. Louis
Abstract Number: 596 Working Group: Aerosol Physics
Abstract We report an experimental observation of ballistic-to-Brownian transition in the chaotic advection of soot particles trapped in a laminar buoyancy-opposed flame. We found that the probability distribution of the particle step-wise turning angles follows the wrapped Cauchy distribution (WCD), commonly used in directional statistics. With an increase in timescale(τ) of observation, the WCD evolves from a delta function to a uniform distribution. This evolution qualitatively agrees with the ballistic-to-Brownian transition revealed from the scaling between particle mean-squared displacement (MSD) and τ. We next propose a theoretical model for the ballistic-to-Brownian transition kinetics. Three parameters of the motion, namely: the shape factor of WCD, the exponent of MSD-τ scaling power-law, and time are unified with simple mathematical expressions. We anticipate the applicability of our results to studying the motion of tracer objects among other systems across disciplines, as long as the turning angle distribution of the tracer can be described with WCD.