Abstract:
Pollak Distinguished Lecture Series 2011
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NOTE The first lecture of Prof. Stone will be on 15/3/11
at Mechanical Engineering - see below.
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Distinguished Lecture, March 17, 2011, 14:30, Taub 337
Title: Unusual Dynamics in Multiphase Flows : (I) Charged Drops, (II) A
Variant on Viscous Fingering, and (III) Shear-Enhanced Diffusion
Abstract: Multiphase flows come in many varieties. In this talk I describe
three different themes we have explored: (i) experiments of drops in an
electric field where oppositely charged drops fail to coalesce if the
electric field is strong enough, (ii) experiments of the collision of a
droplet with a circular post that spans a significant fraction of the
cross-section of a microfluidic channel, and (iii) new results related to
shear-enhanced diffusion of suspensions. In each case, we identify aspects
of our results that are surprising relative to similar systems studied in
the literature. The experiments are compared with models of the fluid
dynamics.
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Distinguished Lecture, March 15, 2011, 16:00,
Mechanical Engineering, Lady Davis 641
Title: Bacteria, Biofilms and Fluid Dynamics: Elementary Flows and
Unexpected Phenomena
Abstract:
Bacterial biofilms have an enormous impact on medicine, industry and
ecology. These microbial communities are generally considered to adhere to
surfaces or interfaces. We investigate two features of such systems: (i) the
influence of shear stress on the adhesion
time of bacteria and (ii) the formation of biofilm streamers, which refers
to suspended filamentous biofilms. The former is important as a precursor to
the eventual development of a biofilm and we highlight our observations and
characterization of this problem. In particular, we have identified that
shear stress enhances the adhesion time of Pseudomonas aeruginosa and we
report the results of experiments with bacterial mutants to better
characterize the phenomenon. In the second problem we focus on bacterial
streamers, which are frequently observed in natural ecosystems where they
play crucial roles by enhancing transport of nutrients and retention of
suspended particles. In particular, we report the formation of biofilm
streamers suspended in the middle plane of curved microchannels under
conditions of laminar flow. We use numerical simulations of the
three-dimensional flow in curved channels to highlight the presence of a
secondary vortical motion in the proximity of the corners, which suggests an
underlying hydrodynamic mechanism responsible for the formation of the
streamers. Thus, we bring together experiments, simulations, and models for
the fluid-structure interaction to rationalize the spatial and temporal
development of bacterial streamers.
Short Bio:
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Prof. H A Stone received PhD in Chemical Engineering at California
Inst. of Technology in 1988. He was professor at Harvard University,
and since 2009 is Dixon professor in Mechanical and Aerospace Engineering
at Princeton University. Prof. Stone has served on editorial boards of
Physics of Fluids, Journal of Fluid Mech., Acta Mechanica and other journals,
and received numerous awards from USA and European academic institutes.
His visit at the is Technion under the award of Israel Pollak Distinguished
Lecture Series 2011.
His research has been concerned with a variety of fundamental problems
in fluid motions dominated by viscosity, convection, diffusion and
surface reactions. His work has frequently featured a combination of
theory, computer simulation and modeling, and experiments. He has made
contributions to a wide range of problems involving effects of surface
tension, buoyancy, fluid rotation, and surfactants. He has also
studied problems concerning the flow of lipid bilayers and monolayers,
and has investigated the motions of particles suspended in such
interfacial layers. More details can be found in
http://www.princeton.edu/mae/people/faculty/stone/
