Hydrodynamics of linear acceleration in Lepomis macrochirus.
Wise, Tyler N.
- In their natural habitat, fish rarely swim steadily. Instead they frequently accelerate and decelerate. In order to truly understand the natural locomotion of a fish, it is necessary to study the maneuvers frequently employed by the fish as it swims. This study looks at the hydrodynamics of linear acceleration produced at various flow speeds by bluegill sunfish, Lepomis macrochirus, a common caran... read moregiform swimmer, in order to determine how axial forces are generated. Many previous studies have looked at steady locomotion in carangiform fishes, but few have looked at linear accelerations. The only current information about fish accelerations come from anguilliform swimmers. Anguilliform swimmers, such as eels, have very flexible bodies, and undulate their whole bodies in order to swim. In contrast, carangiform swimmers move only the posterior portion of the body. This study found that carangiform swimmers increase axial force by simply increasing the total amount of force produced, and not by changing the direction of the force vector in the wake. Anguilliform swimmers altered both their total force and wake orientation. Because of this, carangiform swimmers produce axial forces differently than anguilliform swimmers. Furthermore, this study shows that the pressure changes around a bluegill’s body are largest around its tail. As the fish accelerates, pressure forces act on more areas of the body, and become present at anterior body sections as well. This work provides more insight into the ability of bluegill sunfish to produce axial forces from their caudal fin.read less