Wing folding and twisting synergistically boost lift generation for flapping wing flight

We designed and built a three degree-of-freedom flapping wing platform to study the aerodynamic benefits of wing folding and twisting during flapping flight. We tested this physical model in a wind tunnel with a Strouhal number range of 0.2 – 0.4, typical for animal flight. Motion tracking was employed to ensure that the wing motion closely followed the prescribed motion, while aerodynamic forces and moments were measured using a six-axis load cell. The results show that the air jet produced by wing clapping may be directed by means of controlling the wing twisting, and that the rotational lift generated by rapid wing twisting can be vectored by varying wing folding angles. Finally, the negative lift during upstroke is alleviated by wing twisting. PIV measurements to visualize the directed jet, are planned and will be presented if time permits.