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SUMMARY:Swimming at low Reynolds number - Yeomans\, J (University of Oxfor
 d)
DTSTART:20130801T140000Z
DTEND:20130801T153000Z
UID:TALK46476@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:I shall introduce the hydrodynamics that underlies the way in 
 which microorganisms\, such as bacteria and algae\, and fabricated microsw
 immers\, swim. For such tiny entities the governing equations are the Stok
 es equations\, the zero Reynolds number limit of the Navier-Stokes equatio
 ns. This implies the well-known Scallop Theorem\, that swimming strokes mu
 st be non-invariant under time reversal to allow a net motion. Moreover\, 
 biological swimmers move autonomously\, free from any net external force o
 r torque. As a result the leading order term in the multipole expansion of
  the Stokes equations vanishes and microswimmers generically have dipolar 
 far flow fields. I shall introduce the multipole expansion and describe ph
 ysical examples where the dipolar nature of the bacterial flow field has s
 ignificant consequences\, the velocity statistics of a dilute bacterial su
 spension and tracer diffusion in a swimmer suspension. \n
LOCATION:Seminar Room 1\, Newton Institute
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