Controllable Curvature on Flexible Flapping Plates

Birds have been an inspiration for flapping propulsion for decades. It is well known that bird wings are not flat but have varying curvature along their wingspan. Inspired by this feature, we seek to determine how wingtip curvature affects flapping. We have developed an actuation mechanism which uses a shape memory alloy to bend the two free corners at the end of a flat plate towards one another in the chord-wise direction. The aerodynamic forces and flow field resulting from dynamically altering this chord-wise curvature while flapping are investigated. The frequency of oscillation, stroke angle, flexibility, and tip actuation timing are independently varied to determine their individual effects.