AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
High-Speed High-Resolution Tracking of Micrometer Particle Detachment and Resuspension on Different Surfaces
ASMAA KASSAB, Victor Ugaz, Maria D. King, Yassin Hassan, Texas A&M University
Abstract Number: 194 Working Group: Homeland Security
Abstract In an effort to understand the phenomena behind particle resuspension, the condition under which a transient fluid flow causes single spherical glass beads particles to detach from glass, ceramic and hardwood substrates was investigated experimentally. Initially, individual particles were deposited on the different substrates located at the lower surface of a rectangular 3x4 inch duct by gravitational settling, after which adjustable speed blowers were used to impose air flows from an open entrance at average velocities up to 16 m/s. The trajectory of the individual particle motion immediately before liftoff was precisely captured by continuously monitoring the particles with a high speed camera. The camera image acquisition is synchronized with the blowers to automatically trigger the camera while starting the air flow with a specially designed electric circuit with 2.5 x 10$^-4 s maximum error in time recording.
Particle tracking obtained from high-speed imaging of individual particle trajectories, revealing a complex motion characterized by an initial bouncing or/and rolling motion along the surface prior to liftoff. In general, bigger particles tend to bounce higher and lift off to lower heights compared to smaller sizes especially in the ceramic substrates. The time it will take for the particle to start its initial movement after imposing air flow at 16 m/s is in the range of 0.33 to 2.6 s with no clear dependence on particle size (10-50 micro-meter) or surface roughness (in our experimental range), however that time is expected to increase with decreasing the air velocity. Particles travel 8 times more in the horizontal direction than the vertical direction in a viewing window of (920 x 420) micro-meters. The higher the vertical position the greater the particle velocity and the faster the particle will resuspend and completely leave the contact with the surface.