Levich Institute Seminar Announcement, 05/08/2007
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Dr. David Saintillan
New York University
Courant Institute of Mathematical Sciences
"Instabilities and Dynamics in Suspensions of Self-Locomoting Rods"
Suspensions of swimming micro-organisms are characterized by complex dynamics involving strong fluctuations and large-scale correlated motions. These motions, which result from the many-body interactions between swimming particles, are biologically relevant as they impact effects such as mean particle transport, mixing and diffusion, with possible consequences for nutrient uptake. In this work, we use numerical simulations to investigate aspects of the dynamics and microstructure in suspensions of interacting self-locomoting rods at low Reynolds number. We propose a detailed model that accounts for hydrodynamic interactions based on slender-body theory and encompasses both biological and non-biological locomotion mechanisms. In agreement with previous theoretical predictions, we demonstrate that aligned suspensions of swimming particles are unstable as a result of hydrodynamic fluctuations in the suspending fluid, and we characterize the wavelength selection of this instability in both ordered and random suspensions. In spite of this instability, we demonstrate that a local nematic ordering persists in the suspensions over short length scales and has a significant impact on the mean swimming speed. Consequences of the large-scale orientational disorder for particle dispersion are discussed and explained in the context of generalized Taylor dispersion theory. Dynamics in thin liquid films are also presented, and are shown to be characterized by a strong particle migration towards the liquid/gas interfaces.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:
CURRENT RESEARCH INTERESTS:
Complex fluids, particulate flows, biophysical fluid dynamics, soft-matter physics.