Fish and ships: can fish inspired propulsion outperform traditional propulsion based systems?

摘要

Fish propulsion mechanism is becoming a major research topic. Effort is aimed at understanding the reasons for the high swimming performances of marine creatures and investigating the possibility of applying fish-like propulsion to surface and underwater vehicles. In this paper, two mathematical models were developed and applied to predict thrust in oscillating tail propulsion. The former was based on the classical treatment of M.J. Lighthill, the latter on the calculation of the instantaneous airfoil kinematics and dynamics by means of a numerical procedure. A fish robot prototype and a thrust measuring equipment were developed in order to assess the accuracy and reliability of the analytical models used. The comparison of the analytical and measured thrust values showed that the average thrust values calculated both according to the Lighthill theory and the numerical model well approximate the experimental values. The numerical model falls short in giving a full quantitative evaluation of the thrust, while it gives a convincing qualitative picture of the thrust production cycle. The simplifications and assumptions made are discussed in order to justify some weaknesses of the models used.