Science / Technology - Colloquium
Friday, February 19, 2010
4:00 PM-5:00 PM
Olin Hall
107
The transport of particulate matter in fluids is important to our understanding of many biological and physical phenomena. Here, I discuss two problems concerning the random motion of particles at small Reynolds numbers (Stokes Flows) where viscous forces dominate over particle inertia.
(i) The time reversibility of these flows is a fundamental principle in hydrodynamics. However, recent studies have shown that many-body interactions between particles in sheared suspensions give rise to chaotic dynamics. When the strain is small, the system can self-organized into reversible state, but sufficiently large strain leads to an abrupt transition to irreversibility similar to a phase transition. This phenomenon is studied experimentally in a system with spatially varying strain (i.e. channel flow).
(ii) Understanding the mixing produced by single-celled swimming microorganisms is important in marine ecology (e.g. suspension feeding, biogenic mixing) and reveals interesting microscale physics. To gain a better understanding of the interplay between Brownian motion and flows produced by swimmers, we study the green alga Chlamydomonas reinhardtii. In the absence of swimmers, passive tracer particles exhibit purely Brownian motion. However, passing swimmers give intermittent kicks to the tracers, which result in complex particle trajectories and enhanced diffusion.
Refreshments will be served at 3:30 P.M. in Olin Hall 118
Cost: FREE
Sponsored by: WPI Physics Department, Dr. Erkan Tuzel
Suggested Audiences: College
E-mail:
etuzel@wpi.edu
Phone: 508-831-5391
Last Modified: February 5, 2010 at 1:05 PM
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