Being a wake

Abstract

What does it mean to be a wake? Does being a wake ensure staying a wake? These questions have kept scientists and engineers awake as they tackle the broader issue of whether it is possible to study structure-function relationships in swimming and flying animals based solely on the identification and analysis of the generated fluid wakes. This talk will describe the development and application of new analytical methods that attempt to put the question of being a wake to sleep. The results suggest that many issues of structure and function in animal swimming and flying can be addressed from a perspective that focuses entirely on the interaction between a well-defined vortex wake created by the animal and the fluid surrounding that wake. Since the animal body and appendages are embedded within the wake, it is shown that locomotor performance is more closely related to wake morphology than to body or appendage morphology. This implies that animal morphology may have only an indirect functional (and hence behavioral and evolutionary) importance for locomotion, whereas wake morphology and kinematics are the prime movers. Consequently, studies of morphological diversity in animal wakes might be of greater use in integrative and comparative studies than traditional investigations of animal body and appendage shape. This is especially true where a single wake morphology can be generated by many different combinations of animal morphology and kinematics. Examples demonstrating the importance of being a wake are given from recent studies of swimming by the sea jelly Aurelia aurita and the bluegill sunfish Lepomis macrochirus.