Geometry and Prestrain Effects on the Aerodynamic Characteristics of Batten-Reinforced Membrane Wings

Abstract

To lessen the deterioration of fixed-wing aerodynamic performance associated with chord Reynolds numbers below 100,000, flexible membrane wing designs have been studied and proposed as an alternative for micro air vehicle use. The beneficial effects of a flexible membrane can include higher lift, steeper lift-curve slope, delayed stall, gentle stall characteristics, and greater efficiency. These benefits have been attributed to both the time-averaged and dynamic deformation of the membrane. This work discusses the geometric and prestrain effects on a batten-reinforced, free trailing-edge membrane wing in low-Reynolds-number (50,000) flow. The global aerodynamic forces on the wings with varying wing aspect ratio, cell aspect ratio, and prestrain level were measured. The results show that the aerodynamic advantages of the flexible membrane are retained for the low-aspect-ratio wings. The optimal membrane cell aspect ratio is found to be approximately 1. The comparison of the aerodynamic forces between the low-aspect-ratio membrane wings and the corresponding three-dimensional-printed wings with the time-averaged deformation indicates the importance of membrane dynamic motion for the derived aerodynamic benefits.