Bio-inspired aquatic flapping propulsion: review and recent developments

The advances in the last years in the field of bio-inspired aquatic propulsion, have to do without a doubt with the new capabilities introduced by novel optical measurement techniques for fluids such as particle image velocimetry and the use of increasingly detailed and precise numerical simulations. Thanks to these techniques, progress has been done into ways of implementing engineering systems based on flapping propulsion, and they have allowed a better understanding of the physics of the fluid-structure interaction phenomena. There is a vast amount of open literature describing the swimming of fish and of canonical systems that simulate animal flapping, and as a result, the role of kinematics and flexibility in propulsion, the role of fin shape and how important are three-dimensional effects, and other aspects such as interference with other wakes, are now better understood. In this brief review, the intention is to highlight the most important aspects related to flapping aquatic propulsion and to point out not intensively, some of the recent most influential works.