BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Taylor dispersion comes alive: the dispersion of swimming algae - 
 Otti Croze\, Plant Sciences\, University of Cambridge
DTSTART:20130206T130000Z
DTEND:20130206T140000Z
UID:TALK43344@talks.cam.ac.uk
CONTACT:Aurelia Honerkamp-Smith
DESCRIPTION:The dispersion of passive tracers in pipe/channel flows is wel
 l understood. G.I. Taylor established that the combined action of shear an
 d diffusion causes tracers to disperse with effective diffusivity K = Pe^2
  for laminar flows (K = Re/ln(Re) for turbulent flows). But how do swimmer
 s\, such as algae\, disperse? Shear flow is known to significantly affect 
 the transport of swimming algae in suspension: viscous and gravitational t
 orques bias bottom-heavy swimmers towards regions of downwelling fluid (gy
 rotaxis). With\nMartin Bees\, I recently developed an analytical theory ex
 tending Taylor's analysis to incorporate biased swimming. The theory is ge
 neral. It requires as inputs transport parameters from models of the avera
 ge response to flow of the swimmer of interest. For algae\, two competing 
 models exist: (rotational) Fokker-Planck (FP) and generalized-Taylor-dispe
 rsion (GTD). I will present recent results comparing our analytical predic
 tions and direct numerical simulations (DNS) for algae in laminar and turb
 ulent channel flows. Our results allow us to address the old question of w
 hether GTD is superior to FP. They also highlight how very differently swi
 mmers disperse from passive tracers\, particularly in laminar flows. I wil
 l discuss the practical implications of our findings and connect them with
  my current work on algal bioreactors with Kyriacos Leptos\, Ray Goldstein
 \, and Alison Smith.
LOCATION:MR11\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
END:VEVENT
END:VCALENDAR