Os recentes desenvolvimentos na tecnologia de sistema aeronáutico de geometria variável têm sido motivados principalmente pela necessidade de melhorar o desempenho de aeronaves. O conceito de Morphing Aircraft, por meio da variação da linha de arqueamento, representa uma alternativa para sistemas aeronáuticos mais eficientes. No entanto, para aeronaves de alto desempenho, projetos com estes novos conceitos podem gerar reações aeroelásticas adversas, o que representa uma questão importante e pode vir a limitar esses novos projetos. A compreensão adequada do comportamento aeroelástico devido à variação da linha de arqueamento, particularmente em regimes transônico, compreende uma questão importante. Este trabalho consiste num estudo preliminar das consequências aeroelásticas de um sistema aeronáutico de geometria variável. O objetivo desse trabalho é explorar as repostas aeroelásticas transônicas de um aerofólio com arqueamento variável no tempo. A metodologia para análise aeroelástica é baseada num modelo de seção típica. A integração no tempo do sistema aeroelástico é obtida pelo método de Runge-Kutta de quarta ordem. A representação do escoamento transônico não estacionário foi computada por um código CFD em um contexto de malhas não estruturadas com uma formulação dada pelas equações de Euler-2D. Esses resultados preliminares podem fornecer aos projetistas informações importantes sobre as respostas aeroelásticas de um sistema aeronáutico com variação da linha de arqueamento, permitindo estabelecer um quadro adequado para futuras investigações de controle aeroelástico de sistema aeronáutico de geometria variável. / Recent developments on aircraft variable geometry technologies have been mainly motivated by the need for improving the flight performance. The morphing wing concept, by means of variable camber, represents an alternative towards more efficient lifting surfaces. However, for higher performance aircraft, this technology may lead to designs that create unsteady loads, which may result in adverse aeroelastic responses, which represents an important and limiting issue. Proper understanding of the aeroelastic behavior, particularly in transonic flight regimes, due to variations in camber comprises an important matter. This work is a primary study of aeroelastic consequences of an real-time adaptive aircraft. The objective of this work is to investigate prescribed variations to airfoil camberline and their influence to the aeroelastic response in transonic flight regime. The methodology is based on computational simulations of typical section with unsteady transonic aerodynamics solved with a Computational Fluid Dynamics (CFD) code. The time integration of the aeroelastic system is obtained by Runge-Kutta fourth order. The unsteady transonic flow was computed by a CFD code based on the 2D-Euler equations with unstructured mesh. Prescribed camber variation of a symmetrical airfoil is transferred to the CFD mesh, and aeroelastic responses and loading is assessed. These preliminary results may provide the designers valuable information on the interaction between changes in camber during airfoil aeroelastic reactions, allowing establishing an adequate framework for further aeroelastic control investigations of morphing wings.

Ce travail de thèse porte sur la modélisation dynamique 3D du rein et le suivi d’une tumeur de cet organe. Il s’inscrit dans le projet KiTT (Kidney Tumor Tracking) qui regroupe des chercheurs issus de plusieurs domaines : la modélisation géométrique, la radiologie et l’urologie. Le cadre de cette thèse suit une tendance de mini-invasivité des gestes chirurgicaux observée ces dernières années (HIFU, coelioscopie). Sa finalité est d’aboutir à un nouveau protocole de destruction de tumeurs rénales totalement non-invasif, par la diffusion d’agents physiques (ondes d’ultrasons) à travers la peau et focalisés sur la tumeur. Devant le mouvement et la déformation que le rein présente au cours du cycle respiratoire, la problématique de ces travaux de recherche est de connaître en permanence la position de la tumeur afin d’ajuster à moyen terme la diffusion des ondes en conséquence. / This Ph.D. thesis deals with the 3D dynamic modeling of the kidney and tracking a tumor of this organ. It is in line with the KiTT project (Kidney Tumor Tracking) which gathers researchers from different fileds: geometric modeling, radiology and urology. This work arised from the tendency of nowadays surgical gestures to be less and less invasive (HIFU, coelioscopy). Its goal is to result in a totally non-invasive protocol of kidney tumors eradication by transmitting ultrasound waves through the skin without breaking in it. As the kidney presents motions and deformations during the breathing phase, the main issue is to know the kidney and tumor positions at any time in order to adjust the waves accordingly.

Ce travail porte sur la mise en œuvre de simulations sur des pales de machines tournantes. Une première partie de la thèse porte sur l’amélioration des performances du couplage fluide-structure. Des nouveaux algorithmes sont présentés. Une nouvelle méthode de déformation de maillage est évaluée. Les développements sont validés à partir de plusieurs cas tests. La deuxième partie porte sur l’application des avancées à des machines tournantes. Une première validation est faite sur une hydrolienne. La vibration d’une pale au passage du mat est étudiée. Enfin, des résultats sur une hydrolienne industrielle sont exposés. / A methodology to simulate blades of turbines is developed. A first part is dedicated to improving the performance of the fluid-structure coupling. New algorithms are presented. A new mesh morphing solution is shown. Developments are validated on many test cases. A second part is dedicated to applying the developments on turbines. A first validation is made on a water turbine. The vibration of a blade interacting with a mast is studied. Finally, some results of an industrial water turbine are shown.

It is believed that structures and actuation systems should be tightly integrated together in the future to create fast moving, efficient, lightweight dynamic machines. Such actuated structures could be used for morphing aircraft wings, lightweight actuated space structures, or in robotics. This requires actuators to be distributed through the structure. A tensegrity structure is a very promising candidate for this future integration due to its potentially excellent stiffness and strength-to-weight ratio, and the inherent advantage of being a multi-element structure into which actuators can be embedded. Development of these machines will utilise expertise in several fields, involving kinematics, dynamics, actuation and multi-axis motion control. The research presented in this thesis concerns the study of multi-axis actuated tensegrity structures. A form-finding method has been developed to find stable geometries and determine stiffness properties of the type of tensegrity structure proposed. It has been shown that a tensegrity structure, with practical nodes of finite size, can be designed with actuated members to give shape-changing properties while potentially allowing a good stiffness to mass ratio. An antagonistic multi-axis control scheme has been developed for the tensegrity structure. The describing function technique has been used to analyse the dead band controller in the control scheme, giving a stability criterion. An experimental actuated tensegrity system has been designed and built incorporating pneumatic muscles controlled by switching valves. Mathematical models for the experimental actuated tensegrity system have been developed in detail, including the pneumatic actuation system and the structure geometry. The dynamic behaviour of the tensegrity system has been investigated via several simulation studies, using the developed models and the proposed control scheme. Experimental validation has been successfully conducted. The multi-axis control scheme can accurately control the tensegrity structure to achieve shape changes while maintaining a desired level of internal pre-load. The mathematical models can be used as a basis for further development.

The modern engineering design process includes computer software packages that require approximations to be made when representing geometries. These approximations lead to inherent discrepancies between the design geometry of a part or assembly and the corresponding manufactured geometry. Further approximations are made during the analysis portion of the design process. Manufacturing defects can also occur, which increase the discrepancies between the design and manufactured geometry. These approximations combined with manufacturing defects lead to discrepancies which, for high precision parts, such as jet engine compressor blades, can affect the modal analysis results. In order to account for the manufacturing defects during analysis, mesh morphing is used to morph a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects. The mesh morphing process is improved by providing a novel method to convert heteromorphic shape matching within Sculptor to homeomorphic shape matching. This novel method is automated using Java and the NX API. The heteromorphic to homeomorphic conversion method is determined to be valid due to its post-mesh morphing maximum deviations being on the same order as the post-mesh morphing maximum deviations of the ideal homeomorphic case. The usefulness of the automated heteromorphic to homeomorphic conversion method is demonstrated by simulating manufacturing defects on the pressure surface of a compressor blade model, morphing a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects, performing a modal analysis, and making observations on the effect of the simulated manufacturing defects on the modal characteristics of the compressor blade.

One outstanding challenge to understanding the behaviors of organisms and other complexities found in nature through the use of computational fluid dynamics simulations lies in the ability to accurately model the highly tortuous geometries and motions they generally exhibit. Descriptions must be created in a manner that is amenable to definition within some operative computational domain, while at the same time remaining fidelitous to the essence of what is desired to be understood. Typically models are created using functional approximations, so that complex objects are reduced to mathematically tractable representations. Such reductions can certainly lead to a great deal of insight, revealing trends by assigning parameterized motions and tracking their influence on a virtual surrounding environment. However, simplicity sometimes comes at the expense of fidelity; pared down to such a degree, simplified geometries evolving in prescribed fashions may fail to identify some of the essential physical mechanisms that make studying a system interesting to begin with. In this thesis, and alternative route to modeling complex geometries and behaviors is offered, basing its methodology on the coupling of image analysis and level set treatments. First a semi-Lagrangian method is explored, whereby images are utilized as a means for creating a set of surface points that describe a moving object. Later, points are dispensed with altogether, giving in the end a fully Eulerian representation of complex moving geometries that requires no surface meshing and that translates imaged objects directly to level sets without unnecessary tedium. The final framework outlined here represents a completely novel approach to modeling that combines image denoising, segmentation, optical flow, and morphing with level set- based embedded sharp interface methods to produce models that would be difficult to generate any other way.

abstract With many visual speech animation techniques now available, there is a clear need for systematic perceptual evaluation schemes. We describe here our scheme and its application to a new video-realistic (potentially indistinguishable from real recorded video) visual-speech animation system, called Mary 101. Two types of experiments were performed: a) distinguishing visually between real and synthetic image- sequences of the same utterances, ("Turing tests") and b) gauging visual speech recognition by comparing lip-reading performance of the real and synthetic image-sequences of the same utterances ("Intelligibility tests"). Subjects that were presented randomly with either real or synthetic image-sequences could not tell the synthetic from the real sequences above chance level. The same subjects when asked to lip-read the utterances from the same image-sequences recognized speech from real image-sequences significantly better than from synthetic ones. However, performance for both, real and synthetic, were at levels suggested in the literature on lip-reading. We conclude from the two experiments that the animation of Mary 101 is adequate for providing a percept of a talking head. However, additional effort is required to improve the animation for lip-reading purposes like rehabilitation and language learning. In addition, these two tasks could be considered as explicit and implicit perceptual discrimination tasks. In the explicit task (a), each stimulus is classified directly as a synthetic or real image-sequence by detecting a possible difference between the synthetic and the real image-sequences. The implicit perceptual discrimination task (b) consists of a comparison between visual recognition of speech of real and synthetic image-sequences. Our results suggest that implicit perceptual discrimination is a more sensitive method for discrimination between synthetic and real image-sequences than explicit perceptual discrimination.

<p>This dissertation explores the aeroelastic stability of a folding wing using both theoretical and experimental methods. The theoretical model is based on the existing clamped-wing aeroelastic model that uses beam theory structural dynamics and strip theory aerodynamics. A higher-fidelity theoretical model was created by adding several improvements to the existing model, namely a structural model that uses ANSYS for individual wing segment modes and an unsteady vortex lattice aerodynamic model. The comparison with the lower-fidelity model shows that the higher-fidelity model typical provides better agreement between theory and experiment, but the predicted system behavior in general does not change, reinforcing the effectiveness of the low-fidelity model for preliminary design of folding wings. The present work also conducted more detailed aeroelastic analyses of three-segment folding wings, and in particular considers the Lockheed-type configurations to understand the existence of sudden changes in predicted aeroelastic behavior with varying fold angle for certain configurations. These phenomena were observed in carefully conducted experiments, and nonlinearities - structural and geometry - were shown to suppress the phenomena. Next, new experimental models with better manufacturing tolerances are designed to be tested in the Duke University Wind Tunnel. The testing focused on various configurations of three-segment folding wings in order to obtain higher quality data. Next, the theoretical model was further improved by adding aircraft longitudinal degrees of freedom such that the aeroelastic model may predict the instabilities for the entire aircraft and not just a clamped wing. The theoretical results show that the flutter instabilities typically occur at a higher air speed due to greater frequency separation between modes for the aircraft system than a clamped wing system, but the divergence instabilities occur at a lower air speed. Lastly, additional experimental models were designed such that the wing segments may be rotated while the system is in the wind tunnel. The fold angles were changed during wind tunnel testing, and new test data on wing response during those transients were collected during these experiments.</p> / Dissertation

<p>This dissertation shows that the architecture of steam generators, steam turbines and heat exchangers for power plants can be predicted on the basis of the constructal law. According to constructal theory, the flow architecture emerges such that it provides progressively greater access to its currents. Each chapter shows how constructal theory guides the generation of designs in pursuit of higher performance. Chapter two shows the tube diameters, the number of riser tubes, the water circulation rate and the rate of steam production are determined by maximizing the heat transfer rate from hot gases to riser tubes and minimizing the global flow resistance under the fixed volume constraint. Chapter three shows how the optimal spacing between adjacent tubes, the number of tubes for the downcomer and the riser and the location of the flow reversal for the continuous steam generator are determined by the intersection of asymptotes method, and by minimizing the flow resistance under the fixed volume constraints. Chapter four shows that the mass inventory for steam turbines can be distributed between high pressure and low pressure turbines such that the global performance of the power plant is maximal under the total mass constraint. Chapter five presents the more general configuration of a two-stream heat exchanger with forced convection of the hot side and natural circulation on the cold side. Chapter six demonstrates that segmenting a tube with condensation on the outer surface leads to a smaller thermal resistance, and generates design criteria for the performance of multi-tube designs.</p> / Dissertation

Shape Memory Alloy actuators can be used for morphing, or shape change, by controlling their temperature, which is effectively done by applying a voltage difference across their length. Control of these actuators requires determination of the relationship between voltage and strain so that an input-output map can be developed. In this research, a computer simulation uses a hyperbolic tangent curve to simulate the hysteresis behavior of a virtual Shape Memory Alloy wire in temperature-strain space, and uses a Reinforcement Learning algorithm called Sarsa to learn a near-optimal control policy and map the hysteretic region. The algorithm developed in simulation is then applied to an experimental apparatus where a Shape Memory Alloy wire is characterized in temperature-strain space. This algorithm is then modified so that the learning is done in voltage-strain space. This allows for the learning of a control policy that can provide a direct input-output mapping of voltage to position for a real wire. This research was successful in achieving its objectives. In the simulation phase, the Reinforcement Learning algorithm proved to be capable of controlling a virtual Shape Memory Alloy wire by determining an accurate input-output map of temperature to strain. The virtual model used was also shown to be accurate for characterizing Shape Memory Alloy hysteresis by validating it through comparison to the commonly used modified Preisach model. The validated algorithm was successfully applied to an experimental apparatus, in which both major and minor hysteresis loops were learned in temperature-strain space. Finally, the modified algorithm was able to learn the control policy in voltage-strain space with the capability of achieving all learned goal states within a tolerance of +-0.5% strain, or +-0.65mm. This policy provides the capability of achieving any learned goal when starting from any initial strain state. This research has validated that Reinforcement Learning is capable of determining a control policy for Shape Memory Alloy crystal phase transformations, and will open the door for research into the development of length controllable Shape Memory Alloy actuators.