Back to Departmental Colloquium: Spring 2010
Departmental Colloquium
Date: Thursday, Jan 14, 2010
Time: 4:15PM
Location: JWB 335
Christel Hohenegger
Courant Institute of Mathematical Science
Title |
Understanding the Dynamics and Mechanics of Complex Fluids |
Abstract |
One of the challenges in modeling the transport properties of complex fluids (e.g. many biofluids, polymer solutions, particle suspensions) is describing the interaction between the suspended micro-structure with the fluid itself. Here I will focus on my work in understanding the dynamics of active suspensions – motile bacterial baths are an important example – and also overview my work on characterization and modeling of complex materials such as lung mucus. Suspensions of active particles, like swimming bacteria or artificial micro-swimmers, have been studied intensely over the past few years. Using a recently derived kinetic model, I have investigated the linearized structure of such an active system near a state of uniformity and isotropy. I show that system instability can arise only from the dynamics of the first azimuthal mode in swimmer orientation, that the growth of fluctuations for a suspension of anterior actuated swimmers is associated with a proliferation of oscillations in swimmer orientation, and that at small-scales the system is controlled independently of the nature of the suspension. Finally a prediction about the onset of the instability as a function of the volume fraction of anterior actuated swimmers can be made. Einstein showed that the thermal fluctuations of tracer particles in a fluid can be related to its bulk viscosity. In recent times this observation has been extended and forms the basis of the field of microrheology, which seeks to use statistical quantities to estimate the viscous and elastic properties of materials from very small volume samples. Following the basic model of two-point microrheology, I have developed a Langevin-based model of the coupled fluctuations of two beads in a viscoelastic liquid and from this derive new relations between measurable quantities and fluid response properties. This approach provides a new interpretation to memory response functions, which play a dominant role in numerical simulation of such systems. |
Computational Mathematics
Applied Mathematics
Materials Science