Meeting Abstract
80.6 Monday, Jan. 6 11:30 Streamwise Vortices Destabilize Swimming Bluegill Sunfish (Lepomis macrochirus) MAIA, A.*; SHELTZER, A.P.; TYTELL, E.D.; Eastern Illinois University; Tufts University; Tufts University amresendedamaia@eiu.edu
In their natural environment, fish must swim stably through unsteady flows and notices. Fish can correct heading rapidly, but the corrections take energy. Previous studies have examined the kinematics and energetics of fish interacting with vertical vortices and horizontal cross-flow vortices, but little is known about the effect of streamwise vorticity. Streamwise vortices are produced by ships’ propellers and axial turbines, but also commonly shed by bluff bodies in streams. We set to test the effect of these vortices on swimming bluegill sunfish by introducing an array of four turbines with similar diameter to the experimental fish inside a sealed flow tank. We measured oxygen consumption for seven sunfish swimming at 1.5 body lengths (L)/s for a period of 2.5 hours with the turbines rotating at 2 Hz and with the turbines off (control). Simultaneously, we filmed the fish ventrally and recorded the fraction of time spent maneuvering and accelerating. Separately, we also recorded lateral and ventral video for a combination of swimming speeds (0.5, 1.5 and 2.5 L/s) and turbine speeds (0, 1, 2 and 3 Hz), immediately after turning the turbines on and 10 minutes later to test for accommodation. Bluegill sunfish are negatively affected by streamwise vorticity. Spills (loss of heading), maneuvers, and accelerations were more frequent when the turbines were on than in the control treatment. These unsteady behaviors, particularly acceleration, correlated with an increase in oxygen consumption with streamwise vorticity. Bluegill sunfish are generally fast to recover from roll perturbations and do so by moving their pectoral fins. The frequency of spills decreased after the turbines had run for 10 min, but was still markedly higher than in the control, showing that fish are capable of adapting to streamwise vorticity, but not completely.
