FISH, F.E.: Mechanisms for enhanced maneuverability in organisms of varying flexibility

Maneuverability with respect to turning is critical to the performance of fast swimming animals. Turning is effected by dynamic forces. For many aquatic animals, these forces are dominated by steady non-inertial forces including lift and drag. Animals can use an asymmetrically applied drag to rotate and turn. Appendages modified as paddles can produce this effect which works well in conditions dictated by low velocity, continuous turning and precise control, but incurs a high energy cost. Lift-based maneuvering systems have the advantage of producing a centripetal force to effect turning without incurring a large decelerating drag, but are limited in duration. Animals that use drag-based turning possess rigid bodies with a high degree of stability. Lift-based turning is associated with a flexible body or enlarged control surfaces. Flexible bodies possessed by fish and marine mammals have been shown to permit high levels of performance with respect to turning rate, centripetal acceleration, and turn radius. Rigid bodies do constrain turning performance, however, the inability to bend can be compensated for by the use of appendages and vectored thrust mechanisms.