The fluid dynamics of feeding and swimming in the upside down jellyfish, Cassiopea xamachana

Mathematical Biology and Ecology Seminar
Wednesday, December 2, 2009 - 11:00
1 hour (actually 50 minutes)
Skiles 269
University of North Carolina at Chapel Hill
The Reynolds number (Re) is often used to describe scaling effects in fluid dynamics and may be thought of as roughly describing the ratio of inertial to viscous forces in the fluid. It can be shown that ’reciprocal’ methods of macroscopic propulsion (e.g. flapping, undulating, and jetting) do not work in the limit as Re approaches zero. However, such macroscopic forms of locomotion do not appear in nature below Re on the order of 1 − 10.  Similarly, macroscopic forms of feeding do not occur below a similar range of Reynolds numbers. The focus of this presentation is to describe the scaling effects in feeding and swimming of the upside down jellyfish (Cassiopeia sp.) using computational fluid dynamics and experiments with live animals. The immersed boundary method is used to solve the Navier-Stokes equations with an immersed, flexible boundary. Particle image velocimetry is used to quantify the flow field around the live jellyfish and compare it to the simulations.