Three-Dimensional Averaged Flow Around Rigid Flapping Wings

Abstract

The flow over a Zimmerman wing flapping to approximately ±45 is investigated using stereoscopic particle image velocimetry. Velocity snapshots are taken at various phases of the wing for 12 different chordwise locations while flapping at 5 Hz. These snapshots are divided into 50 different phases and the flow at the same phase and location is averaged to create a three-dimensional average flow field. The phase-averaged velocity fields are used to calculate the phase-averaged vorticity of which iso-surfaces are presented. At the chordwise location of the wing tip and the two closest chordwise locations, velocity field measurements were also acquired at a flapping frequency of 10 Hz. The wing is then moved in the y-direction to show the flow further away from the wing, and snapshots are taken at both 5 and 10 Hz at the three chordwise locations just mentioned. The phaseaveraged results of the snapshots taken at both y-locations are then combined to show how vorticity is created by acceleration/deceleration of the wing and spread through diffusion and convection.