Do fish stir the ocean?

Wednesday, April 14, 2010 - 11:00am - 11:45am
EE/CS 3-180
Jean-Luc Thiffeault (University of Wisconsin, Madison)
Keywords: stirring, mixing, biomixing, Brownian motion.

Abstract: As fish or other bodies move through a fluid, they stir their
surroundings. This can be beneficial to some fish, since the plankton
they eat depends on a well-stirred medium to feed on nutrients.
Bacterial colonies also stir their environment, and this is even more
crucial for them since at small scales there is no turbulence to help
mixing. It has even been suggested that the total biomass in the
ocean makes a significant contribution to large-scale vertical
transport, but this is still a contentious issue. We propose a simple
model of the stirring action of moving bodies through both inviscid
and viscous fluids. In the dilute limit, this model can be solved
using Einstein and Taylor's formula for diffusion (Brownian motion).
We compare to direct numerical simulations of objects moving through a
fluid. This is joint work with Steve Childress and George Lin.
MSC Code: