|Date: Friday, March 30, 2012
Location: 1084 East Hall (3:00 PM to 4:00 PM)
Title: PDE Models of Collective Swimming in Bacterial Suspensions
Abstract: Bacteria are the most abundant organisms on Earth and they significantly influence carbon cycling and sequestration, decomposition of biomass, and transformation of contaminants in the environment. This motivates our study of the basic properties of bacterial behavior and its control. The principal mechanism behind the unique macroscopic properties of bacterial suspensions (e.g. 7-fold reduction of the effective viscosity and a 10-fold increase of the effective diffusivity) is self-organization of the bacteria at the microscopic level --- a multiscale phenomenon. Our goal is the understanding of the mechanism of self-organization, which is a fundamental issue in the study of biological and inanimate systems. Our work in this area includes:
* Analytical and numerical study of dilute and semi-dilute bacterial suspensions. We introduced a so-called semi-dilute model for swimming bacteria that includes pairwise interactions and obtained an explicit asymptotic formula for the effective viscosity in terms of known physical parameters. This formula is compared with that derived in our PDE model for a dilute suspension of bacteria driven by a stochastic torque, which models random reorientation of bacteria ("tumbling"). This comparison leads to a phenomenon of stochasticity arising from a deterministic system and is referred to as "self-induced noise". We also conducted numerical modeling of a large number of interacting bacteria using Graphical Processing Units (GPU).
* Kinetic collisional model (work in progress). We seek to capture a phase transition in the bacterial suspension --- an appearance of correlations and local preferential alignment with an increase in concentration. Collisions of the bacteria, ignored in most of the previous works, play an important role in this study, which is based on the kinetic theory approach.
Collaborators: PSU students S. Ryan and B. Hains, and DOE scientists I. Aronson and D. Karpeev (both Argonne Nat. Lab.)
Speaker: Leonid Berlyand
Institution: Penn State University
Event Organizer: John Schotland firstname.lastname@example.org