Levich Institute Special Seminar Announcement, 10/17/2014
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Leslie Yeo
"Anomalous Nonlinear Film Spreading and Colloidal Dispersion Phenomena in Microscale Flows Excited by MHz Order Substrate Vibration"
The strong nonlinear coupling inherent in the dynamical fluid-structural interaction associated with microscale flows excited by MHz order substrate vibration often give rise to strange and unexpected behaviour. In this talk, we present two such cases and elucidate the underlying fundamental physical mechanisms governing the phenomena. In the first, thin micron order films are observed to emanate from a microlitre sessile drop and subsequently spread with constant velocity in a direction opposing that of the MHz order Rayleigh surface wave excitation (i.e., a surface acoustic wave or SAW). Curiously, the film suffers from a peculiar instability leading to the formation of fingering fronts, not unlike, but quite distinct to, the viscous fingers in Marangoni- or gravity-driven instabilities. Soliton-like wave trains are then observed to grow at the finger fronts and propagate away from the leading edge of the film in the opposite direction to the film spreading. In the second, anomalous poloidal flows are observed to arise in similar sessile drops under similar MHz order substrate vibration, but this time in the form of Lamb waves. Particles suspended in the drop are then seen to be drawn into the poloidal vortex, and subsequently driven to the vortex centre under shear gradients to form toroidal particle rings whose diameters are inversely proportional to the vibration frequency.
BRIEF ACADEMIC/EMPLOYMENT HISTORY
Leslie Yeo is a Professor of Chemical Engineering, an Australian Research Council Future Fellow and Co-Director of the Micro/Nanophysics Research Laboratory. He is also currently an Adjunct Senior Research Fellow in the Department of Physiology at Monash University’s Faculty of Medicine, Nursing & Health Sciences.