Numerical and Experimental Investigation of Wing Flutter Suppression via Distributed Propulsion
Candidate for Master of Science in Mechanical Engineering
Major Professor: Dr. Roberto Albertani

In a seminal paper published in 1982, scientist have warned that humanity was pushing earth’s ecosystems beyond their capacities to support the web of lift. One response to the concern was outlined by NASA with its vision for advanced fixed wing transport aircraft to be environmentally compatible and have revolutionary energy efficiency. Two main areas of focus for advanced fixed wing aircraft are distributed propulsion, for increased efficiency up to 500%, and flutter suppression, to allow for lightweight, flexible, high aspect-ratio wings without flutter instability at high speeds. Technology from both areas of focus are combined in this research to investigate the intersection of distributed propulsion and flutter suppression. Flutter suppression via distributed propulsion was studied through numerical predictions and experimental testing. A wind tunnel test rig was designed and manufactured with a rigid semi-wing affixed to a flexible mount that permits pitch and plunge motion. The rigid semi-wing has 4 electric motors distributed spanwise on the leading edge, mounted at an angle relative to the chord line. A theoretical model, based on pitch and plunge structural dynamics is combined with Theodorsen’s theory of unsteady aerodynamics and motor thrust force for design of the flexible mount, rigid wing, and flutter suppression controller design. Numerical predictions of flexible mount stiffness, natural frequency and free vibration response showed 3-13% agreement with experimental data. Motor thrust was sinusoidally oscillated at frequencies near the systems natural frequencies to demonstrate the authority of the distributed propulsion system in both pitch and plunge vibration modes. Shake-down tests in the wind tunnel showed steady pitch oscillations at 13° angle of attack and 13.5 m/s wind speed. Consistent pitch and plunge oscillations were observed at 15° angle of attack and 14.5 m/s wind speed. The manufactured test rig is a cost-effective solution to study flutter suppression via distributed propulsion.