Vortex dynamics and performance of a flexible plunging airfoil

The kinematic and aerodynamic behaviors of plunging, flexible airfoils were investigated over a parameter space that was representative of birds and flapping MAVs. PIV was used to characterize the velocity fields about the airfoils as it oscillated in a sinusoidal manner, and subsequent vorticity contours were used to map out vortex evolution patterns and wake structures. Qualitative comparisons to a rigid airfoil were performed in order to identify the effects of airfoil deformation on the evolution of the vorticity field. A force transducer was used to determine lift and drag behavior throughout the airfoil's motion. The evolution of the vorticity fields generated by the flexible airfoils were found to adhere to the same categories of wake structures observed for the rigid airfoils, and were primarily dependent on reduced frequency, while aerodynamic loads were strongly correlated with Strouhal number. Finally, a scaling parameter was developed that provided excellent collapse of circulation values for the leading edge vortex within the parameter range investigated for each individual airfoil.