Hydrodynamic modeling of an undulating fin for robotic fish design

Motivated by the interests to develop an agile, high-efficient robotic fish for underwater applications where safe environment for data-acquisition without disturbing the surrounding during exploration is of particular concern, this paper presents computational and experimental results of a biologically-inspired mechanical undulating-fin. The findings offer intuitive insights for optimizing the design of a fin-based robotic fish which has potentials to offer several advantages including low underwater acoustic noise, great maneuverability and better propulsion efficiency at low speeds. Specifically, this paper begins with the design of a robotic fish developed for experimental investigation and for validating computational hydrodynamic models of an undulating fin. A relatively complete computational model describing the hydrodynamics of an undulating fin is given. To analyze the effect of propagating wave motions on the forces acting on the fin surface, the three-dimensional unsteady fluid flow around the undulating fin is numerically solved using computational fluid dynamics (CFD) method. The pressure and velocity distributions acting on the undulating fin have been numerically simulated providing a basis to compute the forces acting on the undulating fin. The computational model has been experimentally validated by comparing the computed thrust coefficient against measured data based on a prototype flexible-fin mechanism.