Experimental Investigation of the Aeroelastic Behavior a NACA0018 Cyber-Physical FlexibleWing

The aeroelastic behavior of a NACA0018, rectangular planform, semi-span aspect ratio (A) of 6, and chord of 0.1 m wing is experimentally explored. Wind tunnel tests were performed over a Mach range from 0 to 0.15 (Re = 220,000) on the test article. The composite wing was designed such that the first torsional mode was isolated and controlled with a motor and feedback control system. This cyberphysical system (CPS) uses dynamic feedback control to make a system behave according to desired equations of motion. The equations of motion can be augmented to replicate any type of dynamics, but for the purposes of this investigation a second-order ordinary differential equation, satisfying Newtonian laws, was used. This research utilized the CPS to investigate the aeroelastic behavior of the wing with varying torsional stiffness, freestream velocity and root angle of attack. Experimental results are qualified by a low-order analytic representation of the aeroelastic phenomenon, aeroelastic data published in the open literature, as well as a high fidelity, fully coupled computational fluidstructural dynamic solver. Two interesting regimes are observed: the case in which the torsional frequency is less than the bending frequency and the inverse relationship. Moreover, a pure stall flutter (excitation of the angular twist) limit cycle oscillation and plunge flutter (excitation of bending mode) are exhibited. Finally, trends between limit cycle oscillations, torsional stiffness, free stream velocity and base angle of attack are observed and discussed. The CPS shows the capability to isolate aero-elastic trends.