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Title:Stability enhancement of a transonic wing using a passive nonlinear energy sink
Author(s):Hubbard, Sean
Director of Research:Bergman, Lawrence A.; Vakakis, Alexander F.
Doctoral Committee Chair(s):Bergman, Lawrence A.; Vakakis, Alexander F.
Doctoral Committee Member(s):McFarland, Donald M.; Geubelle, Philippe H.; Masud, Arif
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Targeted Energy Transfer
Nonlinear Energy Sink
Computational Transonic Aeroelasticity
Abstract:This study examined the use of targeted energy transfer (TET) as a mechanism for passive mitigation of transonic aeroelastic instabilities of a wind-tunnel model wing. Medium- and high-fidelity computational aeroelastic models were used to study the transonic aeroelastic instabilities of the wing and to design a nonlinear energy sink (NES) to enhance stability. Several flutter-suppression mechanisms were identified and it was demonstrated that a properly designed NES can increase the dynamic pressure at flutter by 15% in the transonic dip. Furthermore, it was shown that only one of the suppression mechanisms is robust enough to survive for a wide variety of initial conditions. Based on an effective NES design identified in the computational aeroelastic study, a prototype winglet-mounted NES was designed and built. Computational aeroelastic analysis of the wing, modeled with the winglet and NES using experimentally identified parameters, showed that the prototype improves aeroelastic stability, but external housings for the NES---like the winglet---must be carefully designed to avoid destabilizing effects. To study how the NES affects the dynamics of the wing, a series of experimental and computational ground vibration tests of the wing were performed. They showed that the NES has a profound effect on the second bending mode of the wing, even for small wingtip oscillations. This is a strong indication that the prototype NES will be effective in wind-tunnel tests, because the frequency of the second bending mode is within the range of experimental and computational flutter frequencies of the wing. The final part of this work examined some of the challenges associated with algorithm-based design and optimization of an NES for aeroelastic stabilization. Performance metrics were proposed and robust methods by which to evaluate them were developed. The performance metrics and methods were tested by using a multi-objective genetic algorithm to seek effective NES designs. Analysis of the resulting designs and their performance showed that it is possible to identify the nature of aeroelastic responses and quantify the performance of an NES using simple metrics, but more than one is required to do this effectively. Furthermore, the demonstration showed that optimization algorithms can be used with the proposed performance metrics to design effective NESs.
Issue Date:2014-09-16
Rights Information:Copyright 2014 Sean Hubbard
Date Available in IDEALS:2014-09-16
Date Deposited:2014-08

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