Towards the Body Shape Design of a Hydrodynamically Stable Robotic Boxfish

Ostraciiform fish such as the boxfish are known for their ability to swim smoothly through turbulent waters of coral reefs and their excellent maneuverability. These characteristics are desirable in an micro underwater vehicle. Biologists have recently found that the boxfish´s body shape generates self-correcting trimming forces by shedding counter rotating vortices to compensate for the instabilities in turbulent water. The purpose of this work is to study the effect of body shape on self-correcting vortex generation and use these results to design the outer body shape of a micro underwater vehicle mimicking a real boxfish. To this end, computer aided design and Engineering (CAD/CAE) tools such as solid modeling software and fluid flow simulation software were used for analysis and comparison of different body shapes. In this paper we present the numerical simulation results for two varieties of boxfish, namely the spotted boxfish the Buffalo trunkfish, and the results were used to derive key design guidelines for a suitable body shape that can exhibit the desired self-correcting mechanism. Based on the results an outer shape has been rapid prototyped in two halves that can be mounted on either side of the robot chassis