Speaker: Joyce Lin, University of North Carolina at Chapel Hill
Title: A Falling Sphere Through Strongly Stratified Fluid at Low Reyolds Number

Abstract: Particle settling rates in strongly stratified fluids play a major role in describing a wide variety of biological and environmental phenomena, such as the vertical distribution of biomass and pollution clearing times. Applications can extend to medical issues (such as particle settling rates and stratification in centrifugal separations) and are emerging in increasingly important fields such as microfluidics. At low Reynolds number, we discover that the self- entrainment by a particle in a stratified fluid causes the particle to experience a significantly prolonged settling time. We present data from an experimental investigation and develop a new first principle theory of this phenomenon, with several levels of asymptotic approximations of increasing accuracy. We test these levels through direct comparison with the experimental data, and assess the importance of different asymptotic terms in the model with respect to which dynamical effect needs to be predicted.

Time: Friday, Jan. 23, 2009, 1:30-2:30 p.m.

Place: Science and Tech I, Room 242

Department of Mathematical Sciences
George Mason University
4400 University Drive, MS 3F2
Fairfax, VA 22030-4444
http://math.gmu.edu/
Tel. 703-993-1460, Fax. 703-993-1491