Advances in the visualization and analysis of boundary layer flow in swimming fish

Abstract

In biology, the importance of fluid drag, diffusion, and heat transfer both internally and externally, suggest the boundary layer as an important subject of investigation, however, the complexities of biologcal systems present significant and unique challenges to analysis by experimental fluid dynamics. In this investigation, a system for automatically profiling the boundary layer over free-swimming, deforming bodies was developed and the boundary layer over rigid and live mackerel, bluefish, scup and eel was profiled. The profiling system combined robotics, particle imaging velocimetry, a custom particle tracking code, and an automatic boundary layer analysis code. Over 100,000 image pairs of flow in the boundary layer were acquired in swimming fish alone, making spatial and temporal ensemble averaging possible.