Dissertations / Theses on the topic 'Wings'

Thesis (M.A.)--Wake Forest University. Dept. of Communication, 2008.
Title from electronic thesis title page. Thesis advisor: Mary M. Dalton. Vita. Includes bibliographical references (p. 102-108).

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.
Includes bibliographical references (leaves 43-46).
Human pilots have the extraordinary ability to remotely maneuver small Unmanned Aerial Vehicles (UAVs) far outside the flight envelope of conventional autopilots. Given the tremendous thrust-to-weight ratio available on these small machines [1, 2], linear control approaches have recently produced impressive demonstrations that come close to matching this agility for a certain class of aerobatic maneuvers where the rotor or propeller forces dominate the dynamics of the aircraft [3, 4, 5]. However, as our flying machines scale down to smaller sizes (e.g. Micro Aerial Vehicles) operating at low Reynold's numbers, viscous forces dominate propeller thrust [6, 7, 8], causing classical control (and design) techniques to fail. These new technologies will require a different approach to control, where the control system will need to reason about the long term and time dependent effects of the unsteady fluid dynamics on the response of the vehicle. Perching is representative of a large class of control problems for aerobatics that requires and agile and robust control system with the capability of planning well into the future. Our experimental paradigm along with the simplicity of the problem structure has allowed us to study the problem at the most fundamental level. This thesis presents methods and results for identifying an aerodynamic model of a small glider at very high angles-of-attack using tools from supervised machine learning and system identification. Our model then serves as a benchmark platform for studying control of perching using an optimal control framework, namely reinforcement learning. Our results indicate that a compact parameterization of the control is sufficient to successfully execute the task in simulation.
by Rick E. Cory.
S.M.

What are the biblical cherubim? In the Hebrew Bible, the physical appearance and cultic role of the cherubim are never explicitly elucidated. Largely, the authors assume their audience is familiar with the form and function of these heavenly beings. Yet the portrayal of the cherubim varies from text to text and, sometimes, we are given conflicting information. Previous studies of the cherubim have placed too great an emphasis on archaeological and etymological data. This thesis presents a new synthetic study which prioritises the evidence supplied by the biblical texts. Biblical exegesis, using literary and historical-critical methods, forms the large part of the investigation (chapter 2). The findings arising from the exegetical discussion provide the basis upon which comparison with etymological and archaeological data is made (chapters 3 and 4). It is argued that, with the exception of the book of Ezekiel, the biblical texts are quite consistent in their portrayal of the cherubim. Cherubim are intimately connected with the manifestation of Yahweh and have an apotropaic function in relation to sacred space. They are envisaged with one face and one set of wings. Ps 18:11 = 2 Sam 22:11 suggests that they are quadrupedal. The traditions in the final form of Ezekiel 1-11 mark a shift in the conception of the biblical cherubim. Physically, the cherubim are transmogrified and become enigmatic beasts with four faces and four wings. Their function also changes. Depicted elsewhere as menacing guardians, in Ezekiel they become agents of praise. The results suggest that traditions envisaging the cherubim as tutelary winged quadrupeds were supplanted by traditions that conceived of them as more enigmatic, obeisant beings. In the portrayal of the cherubim in Ezekiel and Chronicles, we can detect signs of a conceptual shift that prefigures the description of the cherubim in post-biblical texts, such as The Songs of the Sabbath Sacrifice and the Enochic texts.

Thesis (D.M.A.) -- University of Maryland, College Park, 2004.
Thesis research directed by: School of Music. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This research work presents a series of investigations into the structural, dynamic and aeroelastic behaviour of composite wings. The study begins with a literature review where the development of aeroelastic tailoring and specific applications of the technology are discussed in detail. A critique of methods for the determination of cross-sectional rigidity properties follows for beams constructed of laminated and thin-walled materials. Chordwise stiffness is shown to be an important parameter that must be considered as it has a significant effect on the amount of bending-torsion coupling present in a beam and, as a consequence, on the value of torsional rigidity. The free vibration characteristics of such beams are then examined using the dynamic stiffness matrix method. Natural frequencies and mode shapes of various beams are studied using the fibre angle, β, and the bending-torsion coupling which is measured (in this study) by the non-dimensional parameter ψ, as design variables. The results show that ψ has only a marginal effect on the natural frequencies of composite beams (wings) but can significantly modify the mode shapes of such beams. It can be used to decouple modes which are geometrically (inertially) coupled in the same way as mass balancing but without a weight penalty. It can also be used to abate the unfavourable coupling introduced by sweep angle. Classical flutter and divergence of swept and unswept uniform cantilever wings are investigated using laminated flat beams (plates) and thin-walled beams of rectangular and biconvex cross-sections. Various parameters, such as, the fibre angle, β, the coupling parameter, ψ, the angle of sweep, Λ, the static unbalance, Xα, and the non-dimensional ratio of the fundamental (uncoupled) bending to fundamental torsional frequency, ωh/ωα, are varied and their subsequent effects on aeroelastic stability are investigated. The importance of torsional rigidity GJ on the flutter of composite wings is shown to be substantial in contrast with ψ, which is generally the most important parameter to be considered when the objective is that of increasing the divergence speed. Modal interchanges in the free vibration and flutter of laminated composite wings are shown to be primarily responsible for behaviour not experienced with metallic wings, in particular the effect of wash-in and wash-out on flutter. The most intriguing features of these investigations, however, are those which show that models adequate for the analysis of composite wings may be based on two parameters, the frequency ratio ωh/ωα and the coupling parameter ψ. Some results are confirmed by independent optimisation studies. Finally, a preliminary investigation is carried out into the flutter suppression and gust alleviation of a laminated composite wing by the use of active controls. The results show that by using an active control in an optimum trailing edge position the gust response of a wing can be significantly alleviated without compromising the already optimised flutter speed by the use of aeroelastic tailoring.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada
The Western Aeronautical Test Range (WATR) of NASA’s Dryden Flight Research Center (DFRC) is facing a challenge in meeting the technology demands of future flight mission projects. Rapid growth in technology for aircraft has resulted in complexity often surpassing the capabilities of the current WATR real-time processing and display systems. These current legacy systems are based on an architecture that is over a decade old. In response, the WATR has initiated the development of the WATR Integrated Next Generation System (WINGS). The purpose of WINGS is to provide the capability to acquire data from a variety of sources and process that data for subsequent analysis and display to Project Users in the WATR Mission Control Centers (MCCs) in real-time, near real-time and subsequent post-mission analysis. WINGS system architecture will bridge the continuing gap between new research flight test requirements and capability by distributing current system architectures to provide incremental and iterative system upgrades.

The physics of flapping is very important in the design of MAVs. As MAVs cannot have an engine that produces the amount of thrust required for forward flight, and yet be light weight, harnessing thrust and lift from flapping is imperative for its design and development. In this thesis, aerodynamics of pitch and plunge are simulated using a 3-D, free wake, vortex lattice method (VLM), and structural characteristics of the wing are simulated as a membrane supported by a rigid frame. The aerodynamics is validated by comparing the results from the VLM model for constant angle of attack flight, pitching flight and plunging flight with analytical results, existing 2-D VLM and a doublet lattice method. The aeroelasticity is studied by varying parameters affecting the flow as well as parameters affecting the structure. The parametric studies are performed for cases of constant angle of attack, plunge and, pitch and plunge. The response of the aeroelastic model to the changes in the parameters are analyzed and documented. The results show that the aerodynamic loads increase for increased deformation, and vice-versa. For a wing with rigid boundaries supporting a membranous structure with a step change in angle of attack, the membrane oscillates about the steady state deformation and influence the loads. For prescribed oscillations in pitch and plunge, the membrane deformations and loads transition into a periodic steady state.
Master of Science

This collection moves chronologically through the events surrounding the Taylor Bridge Fire. In beginning with a series of poems about a time when the speaker worked at Dairy Queen, this speaker’s connection to the landscape becomes apparent, and, as the fire takes center stage, the speaker becomes more of an observer and commentator. The second section begins with the sonnet sequence that I visualized as being an aftermath of the fire. For instance, these fires begin at the close of summer, and by winter, the area is not getting any snow, which means more dry conditions and more drought in the future. Ultimately, the fire drives many animals out of the valley, and, to a certain extent, the speaker is motivated to leave as well because of the destruction. Her departure is an important element of her relationship to her familiar landscape. She leaves, but not really. The last two poems in this collection circle both the reader and speaker back to fire and to the Kittitas Valley.

In this dissertation, neural networks are designed to effectively model static non-linear aeroelastic problems in adaptive structures and linear dynamic aeroelastic systems with time varying stiffness. The use of adaptive materials in aircraft wings allows for the change of the contour or the configuration of a wing (morphing) in flight. The use of smart materials, to accomplish these deformations, can imply that the stiffness of the wing with a morphing contour changes as the contour changes. For a rapidly oscillating body in a fluid field, continuously adapting structural parameters may render the wing to behave as a time variant system. Even the internal spars/ribs of the aircraft wing which define the wing stiffness can be made adaptive, that is, their stiffness can be made to vary with time. The immediate effect on the structural dynamics of the wing, is that, the wing motion is governed by a differential equation with time varying coefficients. The study of this concept of a time varying torsional stiffness, made possible by the use of active materials and adaptive spars, in the dynamic aeroelastic behavior of an adaptable airfoil is performed here. A time marching technique is developed for solving linear structural dynamic problems with time-varying parameters. This time-marching technique borrows from the concept of Time-Finite Elements in the sense that for each time interval considered in the time-marching, an analytical solution is obtained. The analytical solution for each time interval is in the form of a matrix exponential and hence this technique is termed as Matrix Exponential time marching. Using this time marching technique, Artificial Neural Networks can be trained to represent the dynamic behavior of any linearly time varying system. In order to extend this methodology to dynamic aeroelasticity, it is also necessary to model the unsteady aerodynamic loads over an airfoil. Accordingly, an unsteady aerodynamic panel method is developed using a distributed set of doublet panels over the surface of the airfoil and along its wake. When the aerodynamic loads predicted by this panel method are made available to the Matrix Exponential time marching scheme for every time interval, a dynamic aeroelastic solver for a time varying aeroelastic system is obtained. This solver is now used to train an array of neural networks to represent the response of this two dimensional aeroelastic system with a time varying torsional stiffness. These neural networks are developed into a control system for flutter suppression. Another type of aeroelastic problem of an adaptive structure that is investigated here is the shape control of an adaptive bump situated on the leading edge of an airfoil. Such a bump is useful in achieving flow separation control for lateral directional maneuverability of the aircraft. Since actuators are being used to create this bump on the wing surface, the energy required to do so needs to be minimized. The adverse pressure drag as a result of this bump needs to be controlled so that the loss in lift over the wing is made minimal. The design of such a "spoiler bump" on the surface of the airfoil is an optimization problem of maximizing pressure drag due to flow separation while minimizing the loss in lift and energy required to deform the bump. One neural network is trained using the CFD code FLUENT to represent the aerodynamic loading over the bump. A second neural network is trained for calculating the actuator loads, bump displacement and lift, drag forces over the airfoil using the finite element solver, ANSYS and the previously trained neural network. This non-linear aeroelastic model of the deforming bump on an airfoil surface using neural networks can serve as a fore-runner for other non-linear aeroelastic problems. This work enhances the traditional aeroelastic modeling by introducing time varying parameters in the differential equations of motion. It investigates the calculation of non-conservative aerodynamic loads on morphing contours and the resulting structural deformation for non-linear aeroelastic problems through the use of neural networks. Geometric modeling of morphing contours is also addressed.
Ph. D.

UAVs are becoming an accepted tool for sensing. The benefits of deployable wings allow smaller transportation enclosures such as soldier back packs up to large rocket launched extraterrestrial UAVs. The packing of soft inflatable wings and Hybrid inflatable with rigid section wings is being studied at the University of Kentucky. Rigid wings are volume limited while inflatable wings are mass limited. The expected optimal wing design is a hybrid approach. Previous wing designs have been packed into different configurations in an attempt to determine the optimal stowed configurations. A comparison of rigid, hybrid, and inflatable wings will be presented. Also a method for simulating optimally packed wings with respect to geometric constraints will be presented. A code has been written to study soft wing packing and verified the soft wing packing results. This code can be used during initial wing design to help predict wing size and packing configurations. In this thesis, an over view of the packing configurations as well as packing observations will be covered such , packing inefficiencies, wing mounting limits, long term storage, and scaling of packing.

In this study, the non-equilibrium Johnson and King Turbulence Model (JK model) is implemented in a three-dimensional, Navier-Stokes flow solver. The main program is a structured Euler/Navier-Stokes flow solver in which spatial discretization is accomplished by a finite volume formulation and a multigrid technique is used as a convergence accelerator. The aim is the validation of this in-house developed CFD (Computational Fluid Dynamics) tool with this enhanced enlarged capability in order to obtain a reliable flow solver that can solve flows over swept wings accurately. Various test cases were evaluated against reference solutions in order to demonstrate the accuracy of the newly implemented JK turbulence model. The selected test cases are NACA 0012 airfoil, ONERA M6 wing, DLR-F4 wing and two wings taken from the 3rd Drag Prediction Workshop. The solutions were analyzed and discussed in detail. The results show appreciably good agreement with the experimental data including force coefficients and surface pressure distributions.

This research work presents series of investigations into the structural dynamics and dynamic aeroelastic (flutter) behaviour of composite and metal wings. The study begins with a literature review where the development and an over view of the previous investigations in this field are presented. Static stiffness is very important to any type of analysis, especially in both dynamic and flutter analysis as in this case. Therefore, different methods are presented and used for the determination of cross- sectional rigidities such as bending, torsional and bending-torsional coupling rigidities properties for beams constructed of laminated and thin-walled structures materials. A free vibration experimental analysis was conducted on the physical Cranfield Al aerobatic composite wing box structure. The composite wing box was exited in the frequency range of 0 to 300 Hz, with both sinusoidal and random excitations, which yields to six resonant frequencies. The theoretical free vibration and flutter analysis was then carried out firstly on the physical Cranfield Al aerobatic metal wing box. The metal wing was modeled using two techniques; the first model was a simplified wing structure (beam with lumped mass). This analysis of the simplified model was done using CALFUN program for the free vibration analysis and using MSC/NASTRAN for both free vibration and flutter analysis. The second model was a detailed model created by MSC/PATRAN and analyzed by MSC/NASTRAN for the free vibration and flutter analysis. The obtained results (natural frequencies and mode shapes) showed a good agreement between the simplified, detailed model and the experimental test. It was found that even with using the simplified model, but having the physical characteristics of the wing leads to a good agreement with the detailed model and experimental work. This also showed the importance of simplified model at early stage of the design to the structural designer in terms of the accuracy, time, and size of the model. Free vibration and flutter analysis was carried out on the Cranfield Al aerobatic composite wing box with the original laminate lay ups using Lanczos method for extracting the eigenvalues and eigenvectors and using PK method for finding the flutter speed and frequency provided by MSC/NASTRAN. The results were compared with the experimental vibration analysis and were found a large difference in the first frequency mode. To investigate the cause of the variation, a series of static loading tests were performed on the composite wing box. Also a comparison of the results between the metal and composite aerobatic wing box is presented. It was found that the large difference could be due to the combination of different parameters such as stiffness (age of the wing, delamination and boundary condition), and increase of mass of the physical wing box (due to environmental effect such as moisture) and modelling differences. The free vibration characteristics of ten wing models constructed from balanced and unbalanced laminate configurations were carried out using Lanczos method provided by MSC/NASTRAN. The analysis was done on ten wing models modeled to simulate Circumferentially Asymmetric Stiffness (CAS) and Circumferentially Uniform Stiffness (CUS). The static equivalent stiffness was calculated using two different modeling methods for a wide range of fibre angles 0 (- 90° to 90°) of the skins. The variations and the importance of the stiffness ratio (EI/GJ), parameter (K/GJ), and the frequency ratio (wb/(Ot) are illustrated against the fibre angle 0. It was found that the fundamental bending frequency is slightly lower in the case of CUS (K = 0) as compared to the CAS (K # 0), which was not the case in the plate model. Also, the first torsion frequency mode in the case of CUS was much lower than the first torsion frequency of the CAS, which was not the case of the plate model. However, the effect of bend-twist coupling stiffness on the mode shapes was pronounced in both structures especially at the area of higher coupling stiffness. The flutter analysis was done using the PK method for all the wing models of both (CAS) and (CUS) configurations. The results showed the optimum value of flutter speed and the importance of the stiffness ratio (EI/GJ), parameter (K/GJ), the frequency ratio (wb/wt), which will lead to the maximum flutter speed. The effects of the above parameters, geometrical coupling and the wash-in and washout on the non- dimensional flutter speed are presented. It was concluded that, negative bend-twist coupling stiffness is beneficial for flutter speed compared to the positive bend-twist coupling stiffness at 00<0<_30°. It was also found that the flutter speed for the CUS was higher at 00<0<_300 compared to the CAS. Also creating an offsite between the elastic axis and center of gravity (behind) decreases the flutter speed whereas having more ribs increases the flutter speed compared with adding stringers. The analysis was carried out on a more practical composite wing box, which was the physical Cranfield Al aerobatic composite wing box. There are some simplifications on the physical structure, which are the cancellation of the woven materials and keeping the same laminate lay ups for the upper and lower skin. The natural frequency and mode shapes was obtained and plotted against the fibre angle 0 of the upper and lower skin for the (CAS) and (CUS) configurations using both symmetric and asymmetric laminate for the upper and lower skin. The flutter analysis was done for the composite wing box for the same configurations as in the free vibration analysis. The effects of the fibre angle 0 of the upper and lower skin, material coupling stiffness, wash-in and wash-out, and structural damping on the non- dimensional flutter speed and flutter frequencies are illustrated. It was found that in this configurations both structural and bend-twist coupling are exist, negative bend- twist coupling (wash-in) increases the flutter speed compared with the positive bend- twist coupling, and the possibility of increasing the flutter speed at higher frequency ratio, structural coupling and positive bend-twist coupling (wash-out).

This thesis presents a new method of solution for the aerodynamics of finite-span wings, which overcomes the difficulties of the previous methods. The present method uses velocity singularities in the Trefftz plane (situated downstream at infinity) to derive the contributions in the solution of the circulation distribution caused by the changes in the spanwise variation of the wing chord and incidence. The new specific functions derived for these contributions contain both natural and forced symmetry and antisymmetry terms, and thus represent a correct mathematical modeling of the physical problem. The correct mathematical representation of these contributions leads to a highly accurate theoretical solution which is not the case in the previous methods.
The method has been validated in comparison with the results obtained by theoretical methods such as Rasmussen & Smith, and Carafoli for rectangular and tapered wings of uniform incidence, and with panel method (Katz & Plotkin) results. Accurate theoretical solutions have been derived for various wing geometries of aeronautical interest, such as wings with curved leading and trailing edges, and wings with asymmetric incidence variations caused by symmetric and antisymmetric deflection of flaps and ailerons (which are more difficult to model using the panel methods).
Furthermore, the present method of solution has been extended to solve the problem of swept wings. A procedure has been developed to specifically treat this problem.

Studies as early as 1967 have indicated that induced drag of a finite aspect ratio wing can be reduced below that of the classical optimum: the elliptically loaded finite aspect ratio wing by the introduction of spanwise camber into the wing planform. In the current research non-planar wings have been extensively studied both theoretically and experimentally in an attempt to understand the factors which govern their aerodynamic properties. A three degree of freedom traverse has been extensively modified to allow a single tube yawmeter to survey the wake behind a wing accurately and quickly. Results of wake surveys are inferred in the light of the theory advanced by Maskell. A new computational model, The Wing and Free Wake model, which is a combination of classical lifting line theory together with a representation for the wake as it develops downstream, shows that induced drag as calculated by rigid wake methods is a maximum of 18% different to that calculated by the new model for wings with spanwise camber. Extensive experimental studies, both by a wind tunnel balance and by wake surveys, indicate the benefit of wings with negative spanwise camber on the total drag. Maximum reductions in total drag have been found to be in the order of 8% for moderate negative spanwise cambers. The rolling up of the vortex wake has been shown to be of fundamental importance in reducing the induced drag of wings with negative spanwise camber.

The aim of this dissertation is to investigate how culture is represented in the Wings 7 blue textbook and workbook and what implications this may have on learners’ cultural understanding. The research questions are: How is culture represented in the textbook and workbook Wings 7 blue?, and What cultural understanding is promoted through the task design of the learning material Wings 7 blue?The analysis of the learning material draws on the theoretical framework of the Swedish researcher Ulrika Tornberg. The result of our analysis, and first research question, displays that the main focus of the cultural content in the Wings 7 blue textbook is on the mainstream national culture of Britain, typical British behavior, and linguistic readiness.Cultural understanding may be seen as either general cultural understanding, based on Tornberg’s two first perspectives, or as intercultural understanding which can be found in Tornberg’s third and final perspective. The result of the analysis of the tasks shows that both types of cultural understanding are promoted in the workbook, but the possibility for learners to develop their own intercultural understanding is limited, which is the answer to our second research question. This leads to the conclusion that the learning material, by itself, does not cover the complete aim for cultural understanding in the National Syllabus.One might argue that the material should only be seen as a complement to the other tools of the teacher, who can compensate for any missing information in his or her communication with the class. However, according to the large National survey for English, teachers of English mostly use published learning materials and tend to trust that these correspond to the aims of the steering documents.

System reliability based design of aircraft wings is studied. A wing of a light commuter aircraft designed according to the FAA regulations is compared with one designed by system reliability optimization. Both the level III, and the advanced first order, second moment (AFOSM) method are employed to evaluate the probability of failure of each failure element of the system representing the wing. In the level III method the statistical correlation between failure modes is neglected. The AFOSM method allows to evaluate the sensitivity derivatives of the system safety index analytically. Furthermore, it accounts for the statistical correlation between failure modes. The results demonstrate the potential of stochastic optimization, and the importance of accounting for the statistical correlation between failure modes. Finally, it is shown that the problem associated with discontinuity of sensitivity derivatives, encountered when using second order Ditlevsen upper bounds to estimate the system failure probability, is circumvented if a penalty function method is used for optimization.
Ph. D.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2016.
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Abstract : Airborne Wind Energy (AWE) is an emerging field of technology that investigates wind power devices capable of remaining airborne either through aerostatic or aerodynamic forces. Consequently, the heavy and expensive tower of conventional horizontal-axis wind turbines is no longer needed, allowing the AWE device to operate at higher altitudes, where the wind tends to be steadier and stronger and, therefore, more power is available. Another claimed advantage is the reduction on overall costs, especially regarding transportation and installation, due to the absence of the tower to withstand the torque caused by the rotating turbine, thus also requiring a simpler foundation. Several AWE concepts have been proposed, among which the pumping kite stands out as one of the simplest and cheapest, essentially comprising a ground winch where energy is generated, and a tethered wing that can be either flexible or rigid. This dissertation contributes to the field of AWE by addressing the pumping kite in four different aspects. The goal is to serve both as a manuscript for the lay reader with some background on physics, aerodynamics, dynamic systems, classic control and optimization techniques, as well as by specialists in either of these areas who intend to carry out deeper investigations. The first contribution is to revisit in detail important models in the literature used to simulate the flight dynamics, to design and to validate control laws. Namely, the 3D two-tether point-mass wing (to which modifications are proposed), the massless wing in dynamic equilibrium, the course angle dynamics and the logarithmic wind shear model are addressed. The second contribution is a comparative study of flight controllers whose references are computed separately from the ground winch control, in a decentralized topology. A two-loop approach is considered, where the outer loop defines a reference trajectory and generates a reference for the course angle, which is then tracked in the inner loop by manipulating the steering input of the tethered wing. A third contribution is the formulation of an optimization problem to choose the operating parameters of the traction and retraction phases that yield the maximum cycle power. One of the main findings is that, by reeling out at a lower speed than the value that maximizes the traction power, the duty cycle increases and, thereby, also the cycle power. The last major contribution is to reinterpret Loyd?s lift (the pumping kite traction phase) and drag modes as particular cases of the actuator disc considered in the derivation of the Betz limit for power extraction from the wind. The expression for the lift mode power coefficient is formulated using blade element momentum theory.

Energia eólica aérea (Airborne Wind Energy (AWE), em inglês) é uma tecnologia de energia renovável que trata de dispositivos que aproveitam a energia cinética do vento e são capazes de se manter no ar através de forças aerostáticas ou forças aerodinâmicas. Este campo de estudos vem atraindo cada vez mais pesquisas devido a duas grandes vantagens previstas sobre a tecnologia convencional de turbinas de eixo horizontal. A primeira vantagem é que a substituição da torre por cabos de comprimento variável permite ao dispositivo operar em altitudes mais elevadas, onde os ventos tendem a soprar mais consistentemente e a uma velocidade maior, caracterizando, portanto, um potencial energético maior. A segunda vantagem é uma redução substancial nos custos do empreendimento, especialmente nos quesitos de transporte e instalação, devido à ausência de uma torre que deva suportar o torque causado pela operação da turbina. Assim, acredita-se que a fundação para o ponto de ancoragem do sistema também se torna mais simples e barata. Os dispositivos de AWE que mantêm-se em voo através de forças aerodinâmicas são denominados de aerofólios cabeados . Várias estruturas com aerofólios cabeados já foram propostas, dentre as quais destaca-se o pumping kite por ser uma das mais simples e de menor custo. O pumping kite consiste, essencialmente, de duas unidades uma de solo e a outra, de voo com possíveis variações quanto ao tipo de aerofólio (rígido ou flexível), número e função dos cabos, atuadores para controle de voo no solo ou junto ao aerofólio, etc. Em uma das configurações mais usuais, tem-se uma máquina elétrica no solo acoplada a um carretel através de uma redução mecânica. À medida em que o aerofólio descreve uma trajetória que visa maximizar a força de tração no cabo, este desenrola-se do carretel, fornecendo potência mecânica à máquina elétrica que, nessa fase, opera como gerador. Quando o comprimento de cabo atinge um valor pré-determinado, encerra-se a fase de tração e inicia-se a fase de recolhimento, durante a qual a máquina elétrica opera como motor para enrolar o cabo até seu comprimento inicial. Para isto o aerofólio é reconfigurado para uma condição de baixa força aerodinâmica, permitindo o recolhimento com um pequeno gasto energético e, assim, aumentando a potência média entregue à rede (potência de ciclo) ao final deste ciclo com duas fases. A unidade de voo é composta essencialmente pelo aerofólio, por um microcomputador embarcado e pelos atuadores de controle de voo. Esta tese visa contribuir à área de AWE em quatro diferentes aspectos. O objetivo é servir tanto como um documento para o leitor leigo interessado no assunto e que tenha conhecimentos em física, aerodinâmica, sistemas dinâmicos, controle clássico e otimização, bem como uma referência para especialistas que estejam buscando avançar em qualquer uma destas frentes. A primeira contribuição é a discussão em detalhes de alguns modelos importantes usados para a simulação, análise e projeto de controladores de voo para aerofólios cabeados. Dentre estes modelos está o aerofólio ponto de massa com dois cabos, cuja construção é explicada passo-a-passo, incluindo a proposição de pequenas modificações relativas ao efeito da massa dos cabos nas equações de movimento. Em seguida também é feita a derivação do modelo que representa a dinâmica do ângulo de curso ( ângulo de giro ) do aerofólio, que é uma variável frequentemente utilizada para o controle de voo. Um terceiro modelo discutido é o modelo logarítmico que descreve a variação da intensidade média do vento de acordo com o coeficiente de rugosidade do solo. Para fins ilustrativos, o modelo foi interpolado para algumas localidades com base em um banco de dados norte-americano aberto ao público. A segunda contribuição desta tese é um estudo comparativo sobre abordagens para controle de voo em uma topologia decentralizada, na qual as leis de controle da unidade de solo e de voo são computadas separadamente. O controle de voo utiliza uma estratégia com duas malhas em cascata. Durante a fase de tração, uma opção é a malha externa utilizar a lemniscata de Bernoulli como referência para a trajetória de oito deitado desejada para o voo do aerofólio. Com base no erro de seguimento da lemniscata, é gerada uma referência para o ângulo de curso, que é repassada à malha interna. Já para a fase de retração, a referência do ângulo de curso é mantida apontando para o zênite, fazendo com que o aerofólio saia da zona de potência (condição de vento cruzado, crosswind) e possa ser recolhido com baixo gasto energético. Uma outra possibilidade discutida, mais simples, é o uso de apenas dois pontos de atração (atratores) como referência de posição do aerofólio na malha externa, com apenas um dos atratores ativo. Assim que o aerofólio cruza a coordenada azimute de um atrator, o outro torna-se o ativo, levando o aerofólio a executar uma curva e, dessa forma, realizar a trajetória desejada de oito deitado. Devido à descontinuidade no erro de seguimento quando chaveia-se entre os atratores, ocorre uma descontinuidade no sinal de controle, razão pela qual esta estratégia é conhecida como bang-bang . É discutido como o bang-bang pode ser vantajoso no caso de aerofólios cabeados com um curto perímetro (comprimento de arco) da trajetória, situação em que o período de amostragem do controle torna-se relativamente grande, o que dificulta a estabilização do controle. Por outro lado, no caso de trajetórias com perímetro maior, a ausência de um percurso bem definido entre os dois atratores pode resultar em uma trajetória aproximadamente geodésica ( reta angular), afastando-se, assim, das trajetórias ótimas de oito deitado sugeridas na literatura. Neste caso, a opção com a lemniscata de Bernoulli pode tornar-se vantajosa. Para a malha interna do controle de voo também foram investigadas algumas alternativas, entre as quais um controlador proporcional. Usando o modelo da dinâmica do ângulo de curso linearizado em alguns pontos principais, é computado o intervalo do ganho proporcional que garante estabilidade em malha fechada, supondo conhecidos os parâmetros do modelo. Também com base no mesmo modelo do ângulo de curso, projetou-se um controlador de realimentação linearizante que impõe uma dinâmica estável de primeira ordem ao erro de rastreamento da malha interna. Tal controlador linearizante requer, em sua lei de controle, o conhecimento da derivada da referência do ângulo de curso. Dado que esta derivada pode ser difícil de se obter, na prática, com baixo ruído, é investigada uma variante do controlador linearizante sem a mencionada derivada. Considerando, para os três controladores, aproximadamente a mesma constante de tempo do sistema em malha fechada, o controlador linearizante completo obteve o melhor desempenho, seguido pelo proporcional, enquanto o linearizante sem derivada da referência do ângulo de curso ficou com o pior desempenho. Uma terceira contribuição ao estudo do pumping kite é a formulação de um problema de otimização para um ciclo de operação, considerando-se a topologia de controle decentralizado. Já que a lei de controle de voo é computada separadamente da unidade de solo, é necessário determinar os valores de alguns parâmetros de operação cuja escolha pode ter um impacto significativo na potência de ciclo. Mostra-se como a potência média durante a fase de tração varia em função do ângulo de ataque médio, e como o ângulo de ataque base pode ser determinado para operar-se no ponto de máxima potência. A fase de tração é parametrizada em termos de um ângulo de ataque base, uma velocidade de desenrolamento, um ângulo polar médio da trajetória, e um comprimento médio do cabo. Já a fase de retração é parametrizada por meio de dois coeficientes que definem a inclinação das rampas de força de tração e ângulo de ataque base, e dois patamares ao final destas rampas. São consideradas restrições no mínimo ângulo de ataque importante no caso de aerofólios flexíveis e na máxima velocidade de enrolamento alcançada pela máquina elétrica. A ideia é reduzir a força de tração e o ângulo de ataque do aerofólio enquanto a velocidade de enrolamento aumenta e, dessa forma, obter-se uma fase de retração eficiente. Para fins ilustrativos, o problema de otimização é resolvido para os valores de patamar através de uma busca em grid, enquanto os coeficientes de inclinação de rampa são definidos de maneira ad hoc. Entre as principais conclusões está que, para o aerofólio do tipo foil (ram-air) kite com 12 m2 de área projetada sujeito a um vento nominal de aproximadamente 10 m/s, ao desenrolar-se o cabo a 2.3 m/s, o que corresponde a uma redução de 25.8 % com relação à velocidade que maximiza a potência na fase de tração, obtém-se um acréscimo de 9.3 % na potência de ciclo. Com base em um método simplificado para cálculo da potência de ciclo, também é obtida a curva de potência do pumping kite, discutindo-se as suas distintas regiões de operação. A última contribuição desta tese refere-se à interpretação dos aerofólios cabeados como um caso específico do disco atuador considerado na derivação do limite de Betz para extração de potência do vento. No caso do disco atuador, a potência extraída é abstraída como o produto entre o empuxo sofrido pelo disco e a velocidade do vento atravessando o disco. No caso da turbina eólica de eixo horizontal, a potência dá-se pelo produto entre o torque no disco e a sua velocidade angular. Já no caso do modo de sustentação de Loyd (a fase de tração do pumping kite), a potência decorre do produto entre o empuxo no disco e a velocidade de translação do disco no sentido do vento (velocidade de desenrolamento ). Finalmente, no caso do modo de arrasto de Loyd (turbina acoplada ao aerofólio cabeado), a potência aproveitada surge do produto entre a velocidade tangencial do disco e a força de arrasto (empuxo) sofrida pela turbina. A tese é concluída com a formulação da expressão do coeficiente de potência para o modo de sustentação de Loyd, evidenciando-se o problema do cálculo dos fatores de indução axial, radial, e o ângulo de ataque parcial para cada anel do disco.

Computational complexity theory is the study of the inherent difficulty of different computational problems. By determining the complexity class of a problem you can learn a lot about how hard the problem is to solve. For games, their complexity class determines sort of an upper limit to how hard they can be. All NP-complete games can be made to be both extremely difficult to play and to analyze. The purpose of this study is to analyze the computational complexity of the game Wings of Vi, where it is shown to be both NP-hard and in NP, and thus NP-complete.

As a small step towards their long-term vision of one day producing emission free vessels, Wallenius em-ployed, in 2009, Mårten Silvanius to carry out his master thesis for them in which he studied five different concepts to reduce the overall fuel consumption using wind powered systems. The vessel on which his study was performed is the 230 m LCTC vessel M/V Fedora. One of the concepts studied was the bow wing which is thought to generate enough force in the ship direction to profitably reduce the overall wind resistance. His calculations showed that the wing would be the preferred method of the different concepts studied since it was determined cheapest to build, had good payback, had good global drag reducing ef-fects and had a predicted performance of a reduction in fuel cost between 3-5% on a worldwide route.This thesis is conducted mainly to verify the results of Silvanius numerical study. The method chosen is to perform a fully viscous 3-D CFD study on the entire flow around the above water portion of the ship in full scale. A 3-D model is created and the wing is placed using suggestions given by Silvanius.One major limitation in this project was the computational capacity available at the time this thesis was conducted. In order to run some of the viscous grids created the grids had to be severely coarsened. This had a negative impact on the reliability on some of the results.Since it has been difficult to obtain satisfactory solutions, no work has been done to optimize the shape and position of the wing.Nevertheless, one it has been shown that the wing does in fact affect the resistance in a positive way, however nowhere near as much as predicted by Silvanius. This effect needs to be further determined through further calculations, both using CFD and also through experimental wind tunnel testing where alternatives to the wing profile should be tested, e.g. replacing the wing with a vortex generator to further delay the point of separation.

This thesis presents a more accurate and efficient method for the study of finite span wings in steady and unsteady supersonic flows with more computing efficiency.
For steady flows, the boundary conditions are expressed in terms of the source distributions over wing surfaces. Specific theoretical solutions are derived for the calculations of pressure coefficient distribution and the lift, pitching moment, and rolling moment coefficients. The present solutions have been validated for delta and trapezoidal wings by comparison with high order conical flow results based on the theory developed by Carafoli, Mateescu, and Nastase. An excellent agreement was found between these results.
For unsteady flows, the boundary conditions of finite span wings are modeled by using pulsating sources distributing over the wing surface. The present method leads to more accurate solutions for rigid wings executing harmonic oscillations in translation, pitching rotation, and rolling rotation of various oscillating frequencies. These solutions were found in very good agreement with the available high order conical flow solutions obtained by Carafoli, Mateescu, and Nastase.
Then the method has been used to obtain solutions for the flexible wings executing flexural oscillations, which are of interest for the aeroelastic studies in the aeronautical applications.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.
Includes bibliographical references (p. 111-113).
Propulsion considerations unique to the supersonic oblique flying wing, including cycle selection, sizing, and integration were investigated via the development and interrogation of aerodynamic and propulsive synthesis models. These models were an amalgamation of computational tools (MSES), linearized theory, parametric estimation, and quasi D thermodynamic cycle analysis. Lift-to-drag ratio, thrust specific fuel consumption, and nacelle wave drag were examined as intermediate figures of merit that would ultimately impact the final performance metric-namely, range parameter and specific excess power. It was found that higher bypass ratio engines could yield an increase in the range parameter up until a critical mach number, above which the increasing nacelle drag would offset the TSFC reductions to yield a net degradation in range performance. Between the baseline TF30-type cycle and its BPR 2.4 modified variant, this critical mach number was found to be at approximately M 2.0 for TT4/TT2 = 5, and M 2.2 for TT4/TT2 = 6.
(cont.) The OFW whose engine was sized for supersonic cruise was also found to have less excess power throughout the low speed regime and hence, longer climb and acceleration times than a comparable symmetric-wing supersonic aircraft. It was concluded that the OFW's reduced drag at supersonic cruise mitigates the gross oversizing of the engine that is common and inevitable for conventional supersonic aircraft at takeoff. Preliminary investigation of the turntable-mounted engine and slot-inlet have demonstrated their feasibility as viable engine integration concepts, but has also revealed the need for integrated design solutions, such as the development of a novel flat-top airfoil, aggressive S-ducts, and in general, a highly compact engine.
by Yuto Shinagawa.
S.M.

The study of nature inspired flight techniques has represented a fundamental philosophical question for many centuries. The question of flight was answered by the pioneers of aviation using techniques different than nature’s solution, which is by completely separating the propulsive, lift producing and control systems from each other. Here, we are pursuing a more inclusive approach. By using dielectric elastomers and by assessing the performance of different membrane wings configurations, for now at least, we aim to fully integrate the lift producing and control systems into one. This will not only provide the framework for further developing this class of materials to achieve flapping capabilities, but also will enhance the current understanding of the overall material and aerodynamic performance expected from dielectric elastomers. This long term goal can be achieved only by breaking the fundamental question into smaller, more manageable questions. The thesis starts by providing a thorough literature review of dielectric elastomers and aerodynamic studies focused on membranes. An in-depth comparison of natural muscles and of what literature considers smart materials is also included. Three major experiments have been completed and the key results are then included and discussed. These total over 18 months of full time laboratory tests. The four main chapters of the thesis cover three areas of study: material research, modeling research and aerodynamic research. First, the material benchtop test is provided which clarifies the effects of pre-strain on the actuating performance of electro-active membranes. Second, the aerodynamic performance of electro-active membranes for different pre-strains is assessed; we conclude that the non-pre-strained active membranes show good promise by extending the performance window above the values reported for the passive cases. Third, a simple aero-electro-mechanical model for modelling dielectric elastomers used as electroactive membranes is introduced and validated. Fourth, a comprehensive study of loads, membrane deformation and flow confirms the capabilities of electro-active membranes as flow conditioning devices.

The aerodynamics of wings with moderately swept wings continues to be a challenging and important problem due to the current and future use in military aircraft. And yet, there is very little work devoted to the understanding of the aerodynamics of such wings. The problem is that such wings may be able to sustain attached flow next to broken-down delta-wing vortices, or stall like two-dimensional wings, while shedding vortices with generators parallel to their leading edge. To address this situation we studied the flow field over diamond-shaped planforms and sharp-edged finite wings. Possible mechanisms for flow control were identified and tested. We explored the aerodynamics of swept leading edges with no control. We presented velocity and vorticity distributions along planes normal and parallel to the free stream for wings with diamond shaped planform and sharp leading edges. We also presented pressure distributions over the suction side of the wing. Results indicated that in the inboard part of the wing, an attached vortex can be sustained, reminiscent of delta-wing type of a tip vortex, but further in the outboard region 2-D stall dominated even at 13° AOA and total stall at 21° AOA. To explore the unsteady flow field and the effectiveness of leading-edge control of the flow over a diamond-planform wing at 13° AOA, we employed Particle Image Velocimetry (PIV) at a Reynolds number of 43,000 in a water tunnel. Our results indicated that two-D-like vortices were periodically generated and shed. At the same time, an underline feature of the flow, a leading edge vortex was periodically activated, penetrating the separated flow, eventually emerging downstream of the trailing edge of the wing. To study the motion and its control at higher Reynolds numbers, namely 1.3 x 106 we conducted experiments in a wind tunnel. Three control mechanisms were employed, an oscillating mini-flap, a pulsed jet and spanwise continuous blowing. A finite wing with parallel leading and trailing edges and a rectangular tip was swept by 0°, 20°, and 40° and the pulsed jet employed as is control mechanism. A wing with a diamond-shaped-planform, with a leading edge sweep of 42°, was tested with the mini-flap. Surface pressure distributions were obtained and the control flow results were contrasted with the no-control cases. Our results indicated flow control was very effective at 20° sweep, but less so at 40° or 42°. It was found that steady spanwise blowing is much more effective at the higher sweep angle.
Ph. D.

This dissertation presents shape and structural optimization studies on flapping wings for micro air vehicles. The design space of the optimization includes the wing planform and the structural properties that are relevant to the wing model being analyzed. The planform design is parameterized using a novel technique called modified Zimmerman, which extends the concept of Zimmerman planforms to include four ellipses rather than two. Three wing types are considered: rigid, plate-like deformable, and membrane. The rigid wing requires no structural design variables. The structural design variables for the plate-like wing are the thickness distribution polynomial coefficients. The structural variables for the membrane wing control the in-plane distributed forces which modulate the structural deformation of the wing. The rigid wing optimization is performed using the modified Zimmerman method to describe the wing. A quasi-steady aerodynamics model is used to calculate the thrust and input power required during the flapping cycle. An assumed inflow model is derived based on lifting-line theory and is used to better approximate the effects of the induced drag on the wing. A multi-objective optimization approach is used since more than one aspect is considered in flapping wing design. The the epsilon-constraint approach is used to calculate the Pareto optimal solutions that maximize the cycle-average thrust while minimizing the peak input power and the wing mass. An aeroelastic model is derived to calculate the aerodynamic performance and the structural response of the deformable wings. A linearized unsteady vortex lattice method is tightly coupled to a linear finite element model. The model is cost effective and the steady-state solution is solved by inverting a matrix. The aeroelastic model is used to maximize the thrust produced over one flapping cycle while minimizing the input power.
Ph. D.

In many situations the motion of the fluid and the motion of the body must be determined simultaneously and interactively. One example is the phenomenon of subsonic wing rock. A method has been developed that accurately simulates the pitching and rolling motions and accompanying unsteady flowfield for a slender delta wing. The method uses a predictor-corrector technique in conjunction with the general unsteady vortex-lattice method to compute simultaneously the motion of the wing and the flowfield, fully accounting for the dynamic/aerodynamic interaction. For a single degree of freedom in roll, the method predicts the angle of attack at which the symmetric configuration of the leading-edge vortex system becomes unstable, the amplitude, and the period of the resulting self-sustained limit cycle, in close agreement with two wind-tunnel experiments. With the development of modern aerodynamic configurations employing close-coupled canards, such as the X-29, comes the need to simulate unsteady aerodynamic interference. A versatile method based on the general unsteady vortex-lattice technique has been developed. The method yields the time histories of the pressure distribution on the lifting surfaces, the distribution of vorticity in the wakes, and the position of the wakes simultaneously. As an illustration of the method, the unsteady flowfield for a configuration closely resembling the X-29 is presented. The results show the strong influence of the canards on the main wing, including the time lag between the motions of the canards and the subsequent changes in the vorticity and hence the pressure distributions and loads on the main wing.
Ph. D.
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Flutter is a dynamic instability which can result in catastrophic failures of an air vehicle. Preventing flutter can be an important factor in the aircraft design, affecting the structural design. Thus, the weight and performance of the aircraft is also being affected. Understanding the role of each design factor of a wing on the onset of flutter can help designers on the flutter clearance of the aircraft. Analysis to predict flutter, ground vibration tests and flight flutter tests, which are performed to verify that the dedicated flight envelope is clear from flutter, are the most important certification processes in modern aviation. Flight flutter testing is a very expensive process. In flight flutter tests the air vehicle is instrumentated with exciters, accelerometers and transmitters to send the test data simultaneously to the ground station to be analyzed. Since flutter is a very severe instability, which develops suddenly, the data should be followed carefully by the engineers at the ground station and feedback should be provided to the pilot urgently when needed. Low test step numbers per flight, increases the cost of flutter testing. Increasing efforts in pre-flight test processes in flutter prediction may narrow the flight flutter test steps and decrease the costs. In this study, flutter prediction methods are investigated to aid the flutter test process. For incompressible flight conditions, some sample problems are solved using typical section model. Flutter solutions of a simple 3D wing are also performed via a coupled finite element linear aerodynamics approach using the commercial tool Nastran. 3D flutter solutions of the wing are compared with the typical section solutions to see how close can the typical section method predict flutter compared to the flutter analyis using the three dimensional wing model. A simulated flutter test method is introduced utilizing the two dimensional typical section method. It is shown that with a simple two dimensional typical section method, flutter test simulation can be performed successfully as long as the typical section model approximates the dynamic properties of the wing closely.

Thèse (Ph.D.)-- École de technologie supérieure, Montréal, 2005.
"Thesis presented to École de technologie supérieure in fulfillment of the thesis requirement for the degree of doctor of philosophy". Bibliogr.: f. [160]-168. Également disponible en version électronique.

When an aircraft is aerodynamically or structurally damaged in battle, it may not able to complete the mission and the damage may cause its loss. The subject of aircraft battle survivability is one of critical concern to many disciplines, whether military or civil. This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and experimental investigations into the effects of simulated battle damage on the low-speed aerodynamics of a fmite aspect ratio wing. Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations, Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions, and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The prediction of Cp's achieved good agreement upstream and near the damage hole, but showed poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at upstream and higher at downstream. The results showed relatively good agreement for the case of transitional and strong jet incidences but slightly poor for weak jet incidences. From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main characteristics of the weak-jet were illustrated clearly. The increments were relatively small. Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing tests and for all damage locations, there was always a flow structure asymmetry. This was believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet' that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional results but at the weak-jet incidence of 4°. For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the damage effects at low incidence, and over-predicting at high incidences. This suggested therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.

Performance of inflatable wings was investigated through laboratory, wind tunnel and flight-testing. Three airfoils were investigated, an inflatable-rigidazable wing, an inflatable polyurethane wing and a fabric wing restraint with a polyurethane bladder. The inflatable wings developed and used within this research had a unique outer airfoil profile. The airfoil surface consisted of a series of chord-wise \bumps.andamp;quot; The effect of the bumps or \surface perturbationsandamp;quot; on the performance of the wings was of concern and was investigated through smoke-wire flow visualization. Aerodynamic measurements and predictions were made to determine the performance of the wings at varying chord based Reynolds Numbers and angles of attack. The inflatable baffes were found to introduce turbulence into the free-stream boundary layer, which delayed separation and improved performance. Another area of concern was aeroelasticity. The wings contain no solid structural members and thus rely exclusively on inflation pressure for stiffness. Inflation pressure was varied below the design pressure in order to examine the effect on wingtip twist and bending. This lead to investigations into wing deformation due to aerodynamic loading and an investigation of wing flutter. Photogrammetry and laser displacement sensors were used to determine the wing deflections. The inflatable wings exhibited wash-in deformation behavior. Alternately, as the wings do not contain structural members, the relationship between stiffness and inflation pressure was exploited to actively manipulate wing through wing warping. Several warping techniques were developed and employed within this re-search. The goal was to actively influence the shape of the inflatable wings to affect the flight dynamics of the vehicle employing them. Researchers have developed inflatable beam theory and models to analyze torsion and bending of inflatable beams and other inflatable structures. This research was used to model the inflatable wings to predict the performance of the inflatable wings during flight. Design elements of inflatable wings incorporated on the UAVs used within this research are also discussed. Finally, damage resistance of the inflatable wings is shown from results of flight tests.

Use of an inflatable/rigidizable wing is explored for Mars airplane designs. The BIG BLUE (Baseline Inflatable-wing Glider Balloon Launched Unmanned airplane Experiment) project was developed at the University of Kentucky, with an objective to demonstrate feasibility of this technology with a flight-test of an high-altitude glider with inflatable/rigidizable wings. The focus of this thesis research was to design and analyze the wing for this project. The wings are stowed in the fuselage, inflate during ascent, and rigidize with exposure to UV light. The design of wings was evaluated by using aerodynamic and finite element software and wind tunnel testing. The profile is chosen based upon aerodynamic results and consideration of manufacturability of the inflatable wing structures. Flow over prototypes of inflatable/rigidizable and ideal shaped wings were also examined in the wind tunnel. Flow visualization, lift and drag measurements, and wake survey testing methods were performed. Results from the wind tunnel testing are presented along with suggestions in improving the inflatable/rigidizable wings aerodynamic efficiency and use on a low Reynolds number platform. In addition, high altitude wing deployment tests and low altitude flight tests of the inflatable/rigidizable wing were conducted.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 167-177).
Ocean sampling for short-transient underwater phenomena, such as harmful algal blooms, necessitates a vehicle capable of fast aerial travel interspersed with an aquatic means of acquiring in-situ measurements. Vehicle platforms with this capability have yet to be widely adopted by the oceanographic community. The primary difficulties in creating such a vehicle, despite the identical governing equations in the two uid media, is a viable propulsion design that can deliver the wide range of forces required. However, several bird species (including murres, puns, and other auks) successfully achieve dual aerial/aquatic propulsion using a single set of flapping wings, offering an existence proof for favorable ow physics. Flapping wings thereby demonstrate a large force envelope, with capabilities far beyond the limits of static airfoil section coefficients, purely by changing the wing motion trajectory. The wing trajectory is therefore an additional design criterion to be optimized along with traditional aircraft parameters, and could open the door to dual aerial/aquatic robotic vehicles. In this thesis, I discuss multiple realizations of a 3D flapping wing actuation system for use in both air and water. The wings oscillate by the root, and employ an active in-line motion degree-of-freedom. I analyze two types of motions in detail: `aquatic' motions where the wing tip moves downstream during the power stroke of each flapping cycle, and `aerial' motions where the wing tip moves upstream during the power stroke. These types of wing motions are common throughout biology, including auks, in order to enhance aerial lift or provide better control over underwater thrust. By controlling the dynamic wing twist and stroke angle, I demonstrate in experiments the necessary force envelope required for dual aerial/aquatic flight. Additionally, I elucidate the wakes of these complex wing trajectories using dye visualization, correlating the wake vortex structures with simultaneous force measurements. To inform the design space, I also analytically derive a low order state-space adaptation of the unsteady lifting line model for flapping or maneuvering wings of finite aspect-ratio. This nonlinear model is suitable for use in the real-time control of wake-dependent forces, without requiring a detailed memory of the wake. Predictive ow states are distributed over the wingspan, providing local information of the instantaneous wing loading, circulation, and wake. I validate this state-space model against both unsteady vortex lattice methods and experiments from the literature. Finally, I optimize the dual aerial/aquatic apping wing trajectories using the state-space model. This experiment-coupled optimization routine minimizes parasitic oscillation of the wing force, allowing control of the unsteady forces throughout each apping cycle. After optimization, the wing trajectories generate the large force envelope necessary for propulsion in both uid media, and furthermore, demonstrate improved control over the unsteady wake.
by Jacob S. Izraelevitz.
Ph. D.