<p>This dissertation explores the stability of beams, plates and membranes due to subsonic aerodynamic flows or solar radiation forces. Beams, plates and membranes are simple structures that may act as building blocks for more complex systems. In this dissertation we explore the stability of these simple structures so that one can predict instabilities in more complex structures. The theoretical models include both linear and nonlinear energy based models for the structural dynamics of the featureless rectangular structures. The structural models are coupled to a vortex lattice model for subsonic fluid flows or an optical reflection model for solar radiation forces. Combinations of these theoretical models are used to analyze the dynamics and stability of aeroelastic and solarelastic systems. The dissertation contains aeroelastic analysis of a cantilevered beam and a plate / membrane system with multiple boundary conditions. The dissertation includes analysis of the transition from flag-like to wing-like flutter for a cantilevered beam and experiments to quantify the post flutter fluid and structure response of the flapping flag. For the plate / membrane analysis, we show that the boundary conditions in the flow direction determine the type of instability for the system while the complete set of boundary conditions is required to accurately predict the flutter velocity and frequency. The dissertation also contains analysis of solarelastic stability of membranes for solar sail applications. For a fully restrained membrane we show that a flutter instability is possible, however the post flutter response amplitude is small. The dissertation also includes analysis of a membrane hanging in gravity. This systems is an analog to a spinning solar sail and is used to validate the structural dynamics of thin membranes on earth. A linear beam structural model is able to accurately capture the natural frequencies and mode shapes. Finally, the dissertation explores the stability of a spinning membrane. The analysis shows that a nonlinear model is needed to produce a conservative estimate of the stability boundary.</p> / Dissertation

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Bauchau, Olivier; Committee Member: Armanios, Erian; Committee Member: Hodges, Dewey; Committee Member: Ruzzene, Massimo; Committee Member: Stallybrass, Michael.

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dimitri N. Mavris; Committee Co-Chair: Daniel P Schrage; Committee Member: David A. Peters; Committee Member: Dewey H. Hodges; Committee Member: J.V.R. Prasad.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p.87-93). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 210-221).

Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Sept. 3, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Applied Mathematics, Department of Mathematical and Statistical Sciences, University of Alberta." Includes bibliographical references.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Smith, Marilyn; Committee Member: Bauchau, Olivier; Committee Member: Costello, Mark; Committee Member: Moulton, Marvin; Committee Member: Ruffin, Stephen.

An investigation into two distinct novel adaptive structures concepts is performed with a view to improving the aerodynamic efficiency of aircraft wings.The main focus of the work is on the development of a rotating spars concept that enables the adaptive aeroelastic shape control of aircraft wings in order to reduce drag. By altering the orientation of the internal wing structure, it becomes possible to control the flexural and torsional stiffnesses of the wing, as well as the position of the elastic axis. It follows then that control of the aeroelastic deformation is also possible. Consequently, the aerodynamic performance can be tailored, and more specifically the lift-to-drag ratio can be maximised through continuous adjustment of the structure.To gain a thorough understanding of the effect of the concept on a wing, an assumed modes static aeroelastic model is developed, and studies are performed using this. These studies establish guidelines with regards to the effective design of a wing incorporating the rotating spars concept. The findings of these studies are then used to establish a baseline design for a wind tunnel model. A finite element model of this is constructed and aeroelastic analyses are used to improve the model and arrive at the final experimental wing design. The wind tunnel tests confirm analytical trends and the robustness of an approach to automaticallyadapt the structure to maintain an aerodynamic performance objective.The remainder of the work investigates the application of an all-moving wing tip device with an adaptive torsional stiffness attachment as a passive loads alleviation system. Through consideration of the attachment stiffness and position, it is possible to tune the device throughout flight in order to minimise the loads that are introduced into the aircraft structure in response to a gust or manoeuvre. A dynamic aeroelastic wing model incorporating the device is developed and used to perform parameter studies; this gives an insight into the sizing and placement of the device. Next, a finite element representation of a conceptual High Altitude Long Endurance (HALE) aircraft is used as a baseline platform for the device. Aeroelastic analyses are performed for the baseline and modified models to investigate the effect of the attachment stiffness and position on the gust response and aeroelastic stability of the system. The reduced loading within thestructure of the modified aircraft then enables the model to be optimised in order to reduce the mass of the aircraft.

With the increase in length of wind turbine blades flutter is becoming a potential design constrain, hence the interest in computational tools for fluid-structure interaction studies. The general approach to this problem makes use of simplified aerodynamic computational tools. Scope of this work is to investigate the outcomes of a 3D CFD simulation of a complete wind turbine blade, both in terms of numerical results and computational cost. The model studied is a 5MW theoretical wind turbine from NREL. The simulation was performed with ANSYS-CFX, with different volume mesh and turbulence model, in steady-state and transient mode. The convergence history and computational time was analyzed, and the pressure distribution was compared to a high fidelity numerical result of the same blade. All the model studied were about two orders of magnitude lighter than the reference in computation time, while showing comparable results in most of the cases. The results were affected more by turbulence model than mesh density, and some turbulence models did not converge to a solution. In general seems possible to obtain good results from a complete 3D CFD simulation while keeping the computational cost reasonably low. Attention should be paid to mesh quality.

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