This paper compares the wake characteristics and aerodynamic forces for spanwise-tensioned membranes with free and fixed leading edges (LE). LE vibration was generated by placing the membrane within an air flow with a sufficient onset velocity. The flow velocity in the wake of the free or fixed LE membrane was measured using a hot-wire anemometer sensor placed downstream of the trailing edge (TE), and the aerodynamic forces were measured using a pair of load cells. The silicone rubber membrane wings were tested at varying angles-of-attack (−8 to 40°), applied strain (2 to 8%), and a nominal Reynolds number of 55,000. The force results show that the LE vibration increased the lift coefficient but also induced a higher drag penalty, particularly in the pre-stall region, resulting in a lower aerodynamic efficiency than the fixed-LE membranes. As indicated by the hot-wire results, this was due to a considerable broadening of the wake caused by the free LE and a breakdown of the organized fluid-structure interaction and energy spectrum compared to a fixed LE.
Zhang, Z., Wrist, A., & Hubner, J. P. (2017). Effects of leading-edge vibration on a spanwise-tensioned membrane at low Reynolds number. Journal of Fluids and Structures, 69, 441–457. https://doi.org/10.1016/j.jfluidstructs.2016.12.009