Meeting Abstract
The wake of a freely flying Pacific Parrotlet (Forpus coelestis) was examined in still air. With positive reinforcement, the bird was trained to fly from perch to perch through a laser sheet while wearing custom-made laser safety goggles. This enabled a detailed study of the evolution of the vortices shed in the wake using stereo particle image velocimetry at 1000 Hz in the plane transverse to the flight path. The instantaneous lift force that supports body weight was calculated based on the velocity field, using both the Kutta-Joukowski and the actuator disk quasi-steady model. During the first few flaps, both models predict an instantaneous lift that is close to the weight of the bird. Several flaps away from the laser sheet, however, the models predict a decline of the lift to about 50% of the bird’s weight. In contrast to earlier reports for bat wakes in wind tunnels, these findings for bird wakes in still air suggest that the predictive strength of quasi-steady force calculations depends on the distance between the flying animal and the laser sheet.
