Three Dimensional Flow Around a Biomimetic Unbounded Flapping Cantilever

Macro-sized cantilevers oscillating in a fluid have been employed in applications ranging from thermal management to propulsion and represent a realistic tradeoff between full biomimicry and ease of fabrication. Surprisingly, the flow field generated upstream and downstream of the cantilever remains poorly understood. In order to properly control the resulting flow, further experimental and numerical studies are needed. From a two dimensional perspective, comprehensive analysis has been done, primarily through employing a single, very wide cantilever. However, many applications necessitate the usage of oscillating cantilevers whose oscillating amplitude is comparable to their width. As the region of analysis moves closer to a corner, where two edges of the slender cantilever meet, the flow becomes extremely three dimensional, rendering the two dimensional analysis tools less useful. The following paper seeks to further understand the highly three dimensional nature of the flow in addition to providing further insight into optimized flow control. Two perpendicular flow planes are analyzed in order to gather the x, y and z directional flow velocities using standard Particle Image Velocimetry measurements. It is shown that under certain circumstances, the resulting flow is atypical of what one would expect from a simple extrapolation from previous two dimensional flow analyses.