Diversity, mechanics and performance of natural aquatic propulsors [chapter]

F.E. Fish
2006 Flow Phenomena in Nature Volume 1  
Both animals and engineered vehicles must contend with the same physical forces that dictate their performance during movement in water. Due to evolution, animals display a wide diversity of propulsive systems associated with swimming modes, body morphologies, and performance levels. Biologists have classified propulsive modes according to the animals' anatomy (e.g. axial, appendicular), kinematics (e.g. anguilliform, carangiform, thunniform), and propulsive forces (e.g. drag-based, lift-based,
more » ... acceleration reaction). The various swimming modes are associated with different indices of performance (i.e. speed, acceleration, maneuverability) that are dependent on the ecology of the animal. High speed and high efficiency are associated with lift-based propulsion produced by oscillation of rigid, high-aspect ratio hydrofoils (i.e. thunniform mode). However, the propulsive systems and body morphology associated with high levels of acceleration and maneuverability diverge from systems designed for speed and efficiency. Drag-based systems, such as paddling, are relatively inefficient and used at low speeds but allow for precise maneuverability and generalized use of the propulsive appendages. In instances where energy economy is important, animals display behavioral mechanisms to extend range, increase swimming speed, and reduce energy costs. These behaviors include swimming in discrete formations (e.g. schooling, drafting), aerial leaps (e.g. porpoising), intermittent swimming (e.g. burst-andcoast), free-riding (e.g. wave and bow riding, hitchhiking), hydroplaning, and vorticity control. The evolution of aquatic animals has produced a great diversity of morphological designs and propulsive modes that can be exploited for biomimetic engineered systems. However, evolution is not a conscious process and is dictated by variation in the genetic code and multi-functional roles of animals in response to local environments. Strict application of biological systems into engineered systems without defining mission requirements may not produce optimal solution.
doi:10.2495/1-84564-001-2/2a fatcat:rice7744nvdpzdettagferhufe