60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007;
Salt Lake City, Utah
Session MT: Andreas Acrivos Award Lecture: Collective dynamics in suspensions of anisotropic and deformable particles
11:10 AM–11:30 AM,
Tuesday, November 20, 2007
Salt Palace Convention Center
Room: Ballroom FH
Chair: Sandip Ghosal, Northwestern University
Abstract ID: BAPS.2007.DFD.MT.1
Abstract: MT.00001 : Collective dynamics in suspensions of anisotropic and deformable particles*
11:10 AM–11:30 AM
Preview Abstract
Author:
David Saintillan
(Courant Institute)
Dispersions of small particles in a viscous fluid are ubiquitous
in both natural and industrial processes. A major difficulty in
understanding these systems arises from the slow decay of
hydrodynamic disturbances at low Reynolds number, which leads to
long-ranged interactions and results in strong velocity
fluctuations and large-scale correlated motions. In this work, I
will address two problems in which hydrodynamic interactions
result in collective dynamics, with emphasis on the effects of
particle shape and deformability.
I will first address the behavior of suspensions of anisotropic
particles such as rigid spheroids under sedimentation.
Hydrodynamic interactions in these systems result in a
concentration instability, by which the particles aggregate into
dense clusters surrounded by clear fluid. Using newly developed
algorithms, large-scale simulations were performed with the aim
of understanding the mechanism for the instability and of
elucidating the wavenumber selection process reported in
experiments. Simulations in finite containers indeed exhibit a
wavenumber selection, and theoretical arguments suggest that the
size of the concentration fluctuations is controlled by vertical
density gradients that form during the sedimentation process. The
case of deformable particles such as viscous droplets is also
addressed, and theory and simulations both demonstrate that a
similar instability also occurs in these systems.
I will then discuss the dynamics in dispersions of polarizable
Brownian rods in an electric field, a situation of practical
relevance in microfluidic applications involving nano-barcodes.
The polarization of a rod results in the formation of a dipolar
charge cloud around its surface, leading to a non-linear fluid
slip: this phenomenon, termed induced-charge electrophoresis,
causes particle alignment with the applied field and creates a
disturbance flow in the surrounding fluid. A theoretical model
and numerical simulations are developed to describe interactions
in such suspensions, and both demonstrate that induced-charge
electrophoresis results in particle pairings, in good agreement
with experimental observations.
*This work was done in collaboration with Eric S. G. Shaqfeh and Eric Darve (Stanford University)
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.DFD.MT.1