[Amath-seminars] Thursday Seminar tomorrow, Fred Wan Conference Room, Lewis 208, 3:30-4:30

Loyce M. Adams lma3 at uw.edu
Wed May 30 08:54:56 PDT 2018

Hi All,

Tomorrow will be the last Thursday Seminar for the quarter. Note
the time is 3:30-4:30 and it will be in Lewis 208. Please see the
speaker, title, and abstract below.

Loyce Adams


May 31: 3:30-4:30 Fred Wan Conference Room, Lewis Hall 208

Speaker: Saverio Eric Spagnolie
University of Wisconsin

Title: Active matter invasion of a viscous fluid and a no-flow theorem


Suspensions of swimming bacteria in fluids exhibit incredibly rich behavior,
from organization on length scales much longer than the individual particle
size to mixing flows and negative viscosities. We will discuss the dynamics
of hydroddynamically interacting motile and non-motile stress-generating
swimmers or particles as they invade a surrounding viscous fluid, modeled
by coupled equations for particle motions and viscous fluid flow. Depending
on the nature of their self-propulsion, colonies of swimmers can either
exhibit a dramatic splay, or instead a cascade of transverse concentration
instabilities as the group moves into the bulk. An active slender-body
approximation will be introduced and used in a linear stability analysis
of concentrated line distributions of particles, matching the results of
our full numerical simulations. Along the way we will prove a very
surprising "no-flow theorem": particle distributions initially isotropic
in orientation lose isotropy immediately but in such a way that results in
no fluid flow *anywhere* and *at any time*.

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