Low-Speed Maneuvering Hydrodynamics of Fish and Small Underwater Vehicles

Abstract

The low-speed maneuvering by fish and small underwater vehicles is considered. The focus is on fluid engineering rather than on biology. An attempt is made to learn from aquatic animals and apply the distilled knowledge to build maneuvering devices. The work is described in three parts. In the first, the morphology of twenty eight species of fish is considered. They are classified into three categories: low speed highly maneuverable, high speed poorly maneuverable, and an overlapping category, viz., high speed highly maneuverable. The qualitative relationship between the length scales of their fins and maneuvering ability is examined. Next, an obstacle-filled aquarium is built and the maneuvering trajectories of two species of fish that are fast yet maneuverable, are video-taped and digitized. Their performance are compared with those of small underwater vehicles. In this manner, the maneuvering “gap” between nature and engineering which appears to be large, is quantified. Finally, based on their length scales in species offish that are deft in maneuvering, a dorsal-fin based maneuvering device is built and its behavior is studied.