March 5 (Thursday) Mark Grosenbaugh (Woods Hole Oceanographic Institution)
Using Computational Fluid Dynamics to Calculate the Stimulus to the Lateral Line of a Fish
Abstract:
The first half of the talk focuses on the results of numerical simulations of viscous flow due to a small sphere vibrating near a fish, a configuration that is frequently used for experiments on dipole source localization by the lateral line. Three-dimensional meshes are constructed reproducing a previously published experiment, by Kantor and Coombs (2003), of a mottled sculpin responding to a vibrating sphere in a current. Both the fish-body geometry and the vibration of the sphere are explicitly included in the simulations. A large eddy simulation (LES) is used to introduce different levels of ambient turbulence. The behavioral results, in which the threshold sphere vibration amplitude increases with current speed, are explained in terms of the fluid and pressure fluctuations around the fish due to the combined effects of ambient turbulence and self-induced flow features such as vortex shedding.
In the second part of the talk, we examine the assumption, itself, of using a potential dipole to represent fish prey. We do this by simulating the hydrodynamic flow field around a self-propelled zooplankton that is located near a fish and jumps from rest. We quantify the hydrodynamic images formed at the lateral line of the fish due to the zooplankton jumping. We highlight the differences between a self-propelling zooplankton prey and a vibrating sphere in terms of the spatial-temporal hydrodynamic signal patterns.