Limitations on swimming speed: how can natural technologies be utilised?

Biography

Dr Frank Fish is a Professor of Biology at West Chester University. He received a PhD in Zoology from Michigan State University. Frank has published over 100 research articles that focus on the energetics, mechanics, and hydrodynamics of aquatic locomotion by animals and construction of biomimetic robot designs.

Synopsis

Despite improvements in training, technique and conditioning, human swimming performance is limited in terms of speed due to the constraints of biology and physics. In comparison, animals greatly exceed human swimming performance. Examination of the morphology, mechanics and hydrodynamics of animal swimming can provide insights into mechanisms to efficiently reduce swimming effort and avoid constraints on speed. Animals are capable of manipulating flow around the body both passively and actively. Passive mechanisms rely on structural and morphological components of the body. Streamlined, fusiform body designs are ubiquitous in fast-swimming animals to minimise drag. The texture and composition of the skin surface further minimises drag by a reduction in water friction and delay of separation effects. The skin of marine animals is tighter than the integument of humans. The pliability of human skin produces mobile skin folds that add to drag. A particularly limitation to human performance is swimming in close proximity to the water surface. This position generates waves that increase drag. In addition, interference within the wave pattern traps the swimmer within a trough that produces a barrier to maximum speed. Active mechanisms by animals for enhanced propulsion utilise vorticity control for thrust production. Fast-swimming animals move their appendages in an oscillatory manner in which wing-like blades produce lift as the primary propulsive force. Humans swim with a paddling, drag-based mechanism. Although effective for propulsion, drag-based swimming is limited to use at low speeds and has reduced efficiency, whereas lift-based mechanisms operate at high speeds with high propulsive efficiency. The thrust is produced in association with the momentum shed by the swimmer into the water. The manifestation of this shed momentum is the wake, which is composed of a thrust producing jet and alternating pairs of vortices. The pattern of vortices for humans indicate severe limits to the fastest speed that can be attained. Compared to human swimmers, aquatic animals have an advantage of being adapted to life in water that permits greater swimming performance than for humans.