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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Influência da asa em gaivota nos coeficientes aerodinâmicos de uma aeronave / Influence of gull wing on the aerodynamic coefficients of an airplane

Átila Antunes França Barbosa 02 September 2015 (has links)
Desde o início da década de 2010, o aumento do preço do combustível de aviação e a pressão da sociedade para redução da emissão de gases nocivos ao meio ambiente, junto com a necessidade de redução de ruído durante as fases de decolagem e pouso, levaram as companhias aéreas a buscar aeronaves mais eficientes. Para suprir essa demanda, os fabricantes de aviões comerciais solucionaram esse problema através do uso de motores de maior desempenho, que apresentam maior diâmetro que motores de gerações passadas. Desse modo, foi necessário projetar asas com maior diedro na região da raiz, possibilitando a instalação desses novos motores, e diedro menor após a seção do motor, adotando assim a solução de asa em gaivota. O presente trabalho visa analisar o impacto de diferentes tipos de asas em gaivota nos coeficientes aerodinâmicos de uma aeronave de configuração comercial típica. Para tanto, foi realizada uma revisão bibliográfica dos estudos envolvendo asas em gaivota. Numa primeira fase foi feito um estudo analítico das características aerodinâmicas de alguns modelos de aeronaves com asa em gaivota, e em uma segunda fase, foram empregadas ferramentas computacionais para analisar seus comportamentos aerodinâmicos. Posteriormente, em uma terceira fase, esses modelos foram ensaiados no túnel de vento do LAE (Laboratório de Aerodinâmica da EESC/USP), e os resultados das três fases foram comparados. / Since the beginning of the 2010s, the increasing price of aviation fuel and the pressure of society to reduce the emission of harmful gases into the environment, coupled with the need of noise reduction during the takeoff and landing, induce carrier companies to look for more efficient airplanes. To furnish this demand, the airplane manufacturers solved the problem using high performance engines, which present a larger diameter than the engines from previous generations. Thereby, it was necessary to project wing with higher dihedral on the root portion, enabling the installation of these new engines, and a lower dihedral after the engine section, thus adopting a gull wing solution. This research project aims at analyzing the impact of different types of gull wing on the aerodynamic coefficients of a typical commercial configuration airplane. For this purpose, a bibliographic review about the studies related to gull wings was performed. In a first phase, an analytical analysis of the aerodynamic characteristics of some airplane model with gull wings was done, and in a second phase, computational programs was used to study their aerodynamic behavior. Later, in a third phase, these models were tested in the wind tunnel of LAE (Laboratory of Aerodynamics of EESC/USP), and the results from the three phases were compared.
42

Etude aéroacoustique de configurations génériques de dispositifs hypersustentateurs : approches analytique et expérimentale

Lemoine, Benoît 24 January 2013 (has links)
Depuis plusieurs décennies, le trafic aérien ne cesse de croître. Ainsi, près de 6 milliards de passagers transitent dans le monde par an. Les objectifs européens à l’horizon 2020 en terme d’émission sonore des aéronefs imposent une réduction de 10 dB par point de mesure par rapport aux aéronefs de l’an 2000. Dans ce contexte, le projet européen VALIANT (VALidation and Improvement of Airframe Noise prediction Tools) a pour but principal de tester, valider et améliorer les codes numériques et les modèles de prédiction du bruit de cellule (trains d’atterrissage + voilure) sur des géométries simplifiées afin de disposer de cas tests pour les recherches futures. L’objectif de la thèse, associé à la contribution de l’ECL dans ce projet, est de créer des bases de données expérimentales fiables sur des systèmes à deux éléments – bec/aile et aile/volet – et de modéliser analytiquement le bruit issu de tels systèmes. La thèse s’est concentrée sur un système aile/volet non porteur et parallèle dans un écoulement de soufflerie à veine ouverte, en configuration d’alignement ou de recouvrement partiel, menant à de possibles interactions aérodynamiques et/ou acoustiques. Les mesures ont été faites pour différentes vitesses d’écoulement (30 − 100 m~s), avec une attention particulière à 50 m~s (M0 ∼ 0, 15). Le taux de turbulence de l’écoulement incident est modifiable par l’ajout d’une grille de turbulence à maille large placée dans la section de sortie du convergent. Les résultats aérodynamiques (fil chaud, pression en paroi) ont révélé la présence d’une forte interaction lorsque la distance entre les deux corps est de l’ordre de grandeur de la couche limite turbulente au bord de fuite de l’aile. De plus, le couplage acoustique a lieu lorsque la longueur de recouvrement est positive ou nulle. Des mesures de localisation de sources menées par l’ONERA/DSNA ont permis de valider les mesures de champ lointain en confirmant l’absence de sources de bruit d’installation en dessous de 10 kHz. Par ailleurs, des comparaisons avec les simulations numériques donnent de bons accords. Du point de vue analytique, le problème mathématique de deux plaques planes en recouvrement partiel dans un écoulement uniforme a été posé et une réduction bidimensionnelle a été justifiée. Le problème n’ayant pas de solution exacte, plusieurs modèles issus de la littérature – théories de Howe et d’Amiet – ont été étudiés. Les plus pertinents ont été confrontés aux résultats expérimentaux, révélant les limites asymptotiques de ces modèles. Un modèle original est alors proposé pour la géométrie du problème posé, sans hypothèse restrictive. La démarche est basée sur une procédure de diffraction itérative permettant de prendre en compte la proximité des deux corps et utilisant la fonction de Green exacte du demi-plan en écoulement uniforme. Le modèle prédit des comportements qualitatifs angle/fréquence proches des résultats expérimentaux. La prise en compte de la statistique des rafales incidentes reste néanmoins à effectuer afin de procéder à des comparaisons quantitatives. Une campagne expérimentale complémentaire avec une marche descendante permet de mettre en évidence les écoulements de cavité arrière d’une aile, plus proche de la réalité. De même, des mesures sur une configuration bec/aile a été testée et la prise en compte de la déflexion du jet de la soufflerie pour la réfraction des ondes sonores par la couche de cisaillement a été proposée. / Air traffic still grows from decades, with yearly 6 billion passengers nowadays in the world. By 2020, the EC imposes aircraft noise reductions by 10 dB per measuring point with respect to the status in 2000. In this context, VALIANT (VALidation and Improvement of Airframe Noise prediction Tools) is an EC-supported project that aims at testing, validating and improving numerical codes and analytical/theoretical models for the prediction of airframe noise (landing gears + high-lift devices) in simplified configurations in order to generate test cases for research needs. The main objective of the thesis in connection with ECL contribution in the scope of VALIANT project is to generate reliable experimental databases for 2-element systems – slatwing and wing-flap – as well as to analytically model overlapping configurations. It is particulary focussed on the experimental and analytical studies of a non lifting wing-flap system in a parallel flow, in aligned and overlapping arrangements. This is aimed at discussing likely aerodynamic and/or acoustic interactions. The tests have been carried out in an open-jet anechoic wind-tunnel for each arrangement and for several flow speeds (30-100 m/s), with main interest on 50 m/s (M0 ∼ 0, 15). The turbulence rate could be changed by fixing a removable turbulence grid with a large mesh at the outlet cross-section of the duct. Aerodynamic results (hot-wire anemometry, wall-pressure) show a strong interaction when the wing-flap distance is about the wing trailingedge boundary layer thickness. Acoustic coupling can be pointed out in cases of overlap. Source localization tests performed by ONERA/DSNA have permitted to validate far-field acoustic tests since no installation effect source seems to strongly radiate below 10 kHz. A good agreement with numerical simulations has been shown for every test. In order to predict noise analytically for a 2-element system in case of overlap in a uniform flow, the mathematical statement has been defined and a 2D-reduction of the equation system can be justified. Since no exact solution exists, several models from the literature – Howe’s and Amiet’s theories – have been studied. Comparisons between overlapping half-planes and slotted trailing-edge models proposed by Howe and experimental results show obvious limitations in the predictions. Then, an original model is proposed involving two bodies in close overlap arrangement, with no assumption. It is based on an iterative scattering procedure to take into account the close vicinity of the two bodies, using the exact half-plane Green’s function in a uniform flow. Convergence is relatively quick and qualitative predictions in angle/frequency behaviour show a good agreement with experiments. However, the statistics of the vortical flows responsible for the sound must be implemented for better comparisons. Other experiments have been done with a backward-facing step – it represents wing trailing-edge cove – to make cavity flow mechanisms appear, such as what is observed in real HLD. Finally, a series of tests has been performed involving a slat-wing system and an angular correction due to refraction of sound waves in shear-layer for a deflected jet has been proposed.
43

Mechanical Design, Analysis, and Manufacturing of Wind Tunnel Model and Support Structure / Mekanisk design, analys och tillverkning av vindtunnelmodell och stödstruktur

Penela Guerrero, Luis Alfonso January 2022 (has links)
The use of wind tunnel models for aerodynamic research is nowadays indispensable to aviation progress in the last years as aircrafts have become more complex. Wind tunnel model design and manufacturing has adopted many different processes and materials such as the use of a five-axis CNC; making this process a relatively long and expensive one. Composite materials offer a good trade-off between ease and cost of manufacturing compared to the more traditional methods, especially for in-house-built prototypes. This volume covers the different phases from design to manufacturing of a wind tunnel model for the MK18 conceptual blended wing-body UAV designed by KTH Green Raven Project students.The model is a down-scaled 1.5 meter span version with a belly-mounted two-strut support. The main structural requirements for the model are to withstand the aerodynamic loads obtained via CFD simulations. A mechanical interface for the support structure connection was designed. Carbon fiber reinforcement with an epoxy resin matrix was selected as the constituents for the airframe skins. A finite element model of the design was developed by using Abaqus to verify the overall structural behavior and stability. The manufacturing strategy of the airframe skins involved producing lightweight fiberglass molds out of CNC milled MDF male patterns and using vacuum infusion process to obtain the final carbon fiber parts. The internal structure members were manufactured out of different materials and processes from water-jet cutting of aluminum profiles to 3D-printed plastic components. The FEA study results showed that the model withstands the maximum loads with a high safety factor and a wing-tip deflection of less than 2\% of half the wingspan. The manufacturing of the molds turned out to be longer and more complicated than expected, but with overall good results. The composite skins came out with good mechanical and surface quality. The total weight of the model resulted in approximately 4.5 kg. Pressure taps were positioned and installed on the model skins. Their respective tubes routed in CAD to visualize the networking for manufacturing. This ensured proper placement to balance ease of installation with meaningful data collection. / Användningen av vindtunnelmodeller för aerodynamisk forskning är idag oumbärlig för flygets framsteg eftersom flygplan de senaste åren har blivit mer komplexa. Vindtunnelmodelldesign och konstruktion har använder många olika tillverkningsmetoder och material såsom femaxlig CNC; vilket gör processen relativt långsam och dyr. Kompositmaterial ger en bra avvägning mellan enkelhet och tillverkningskostnad jämfört med de mer traditionella metoderna, särskilt för egenbyggda prototyper. Denna rapport behandlar faserna från design till tillverkning av en vindtunnelmodell för en konceptuell blended wing-body UAV, MK18, konstruerad av KTH Green Raven Project­studenter. Modellen är en nedskalad version med 1,5 meter spännvidd som monteras på ett bukmonterat, tvådelat stöd. De viktigaste kraven på modellen är att kunna motstå de aerodynamiska belastningarna som beräknats via CFD­simuleringar. Den interna strukturen i modellen utformades för att integrera anslutningen med stödstrukturen. Kolfiber tillsammans med en epoxihartsmatris valdes som beståndsdelar för flygplanets skal. En finit elementmodell av designen utvecklades med hjälp av Abaqus FEA för att verifiera det övergripande strukturella beteendet och stabiliteten. Tillverkningsstrategin för flygplansskalet innebar att man tillverkade lätta glasfiberformar på CNC­frästa MDF­hanformar och använde en vakuuminfusionsprocess (VIP) för att erhålla de slutliga kolfiberdelarna. De inre strukturdelarna tillverkades av olika material och processer från bearbetning av aluminiumprofiler till 3D­utskrivna plastkomponenter. FEA­studieresultaten visade att modellen tål de maximala belastningarna med en hög säkerhetsfaktor och uppvisar en utböjning vid vingspetsarna på mindre än 2% av halva spännvidden. Tillverkningen av formarna visade sig ta längre tid och vara mer komplicerad än väntat, men gav övergripande goda resultat. Kompositskalet visade sig ha god mekanisk ytskvalitet. Modellens totala vikt blev under 5 kg. Hål för tryckmätning placerades också på modellens skal och rören drogs i en CADmodell för att visualisera nätverket för tillverkning. Detta säkerställde korrekt placering för att balansera enkelhet i installationen med meningsfull datainsamling.
44

Feasibility Study for Testing the Dynamic Stability of Blunt Bodies with a Magnetic Suspension System in a Supersonic Wind Tunnel

Sevier, Abigail 05 June 2017 (has links)
No description available.
45

Mechanical Design, Analysis, and Manufacturing of Wind Tunnel Model and Support Structure / Mekanisk Design, Analys och Tillverkning av Vindtunnelmodell och Stödstruktur

Ghika, Sara January 2021 (has links)
This volume covers the phases from design to manufacturing of a wind tunnel test support structure for a conceptual blended wing-body UAV designed by KTH Green Raven Project students. The innovative aircraft design demonstrates sustainability within aviation by utilizing a hybrid electric-fuel cell propulsion system. The wind tunnel test to be conducted at Bristol University will produce data to evaluate the aerodynamic properties of the model for design verification. The wind tunnel model is a small-scaled 1.5m-span model supported by struts that change the pitch and yaw angles during testing. An external force balance provided by Bristol University measures the loads and moments experienced by the model. The main requirements for the structure are to withstand the aerodynamic loads imposed by the model and to change the model's orientation while maintaining wind speed during the test. The maximum aerodynamic loads were provided in a matrix, the largest of which was used as the load condition for the support equating to a 512N lift at 14 degrees AOA. Trade studies were conducted to determine the mechanisms to satisfy the requirements while staying within budget. The chosen design for the support structure includes a circular base plate constrained by a locking ring with positioning pins to change the yaw angle. The main strut is mounted at the the center of the circular base plate. A hinge bracket at the top of the strut interfaces with another hinge bracket within the model via a clevis pin. An electric linear actuator mounted downstream of the main strut is used to vary the pitch angle, with the center of rotation at the clevis pin. Once the design was finalized, finite element analysis was done to verify the structural stability of the design. The FEA results were compared to Euler-Bernoulli approximations for deflection. Manufacturing of the components was out-sourced while assembly and programming of the actuator was done in-house. / Det här examensarbetet är en del av ett projekt som omfattar processen från design till tillverkning av en vindstunnelstödstruktur för en konceptuell UAV av typen flygande vinge, designad av KTH Green Raven Project-studenter. Den innovativa flygplanskonstruktionen visar hållbarhet inom flygindustrin genom att använda hybridbränsleceller som framdrivningssystem. Vindtunneltest som genomförs vid Bristol University kommer att producera data för att utvärdera de aerodynamiska egenskaperna hos modellen för verifiering av designen. Vindtunnelmodellen är en nedskalad modell på 1,5 m som stöds av stag som ändrar anfalls- och girvinklarna under testningen. En extern mätsond från Bristol University mäter de krafter och moment som modellen utsätts för. De viktigaste kraven för konstruktionen är att motstå de aerodynamiska lasterna som modellen påför och att ändra modellens orientering samtidigt som vindhastigheten bibehålls under testet. De maximala aerodynamiska belastningarna tillhandahölls i en matris; varav den största användes som lastfall för stödet motsvarande en 512N lyftkraft vid 14 graders anfallsvinkel. Jämförande studier genomfördes för att bestämma mekanismerna för att uppfylla kraven samtidigt som de låg inom budgeten. Den valda konstruktionen för stödkonstruktionen består av en cirkulär basplatta som fixeras med hjälp av en låsring, och som har positioneringsstift för att ändra girvinkeln. En huvudstång är monterad i mitten av basplattan upp till ett gångjärnsfäste i modellen. Bakom detta sitter ett linjärt ställdon som dras ut och skjuts ihop för att ändra modellens attityd med rotationscentrum vid det övre fästet på huvudstaget. När designen slutfördes gjordes en finit elementanalys för att verifiera dess strukturella stabilitet. FEA-resultaten jämfördes med Euler-Bernoulli-uppskattningar för utböjning. Tillverkningen av komponenterna överläts till extern part, medan monteringen och programmeringen av ställdonet gjordes internt.
46

An Extended Calibration and Validation of a Slotted-Wall Transonic Wall-Interference Correction Method for the National Transonic Facility

Bailey, Matthew Marlando 26 November 2019 (has links)
Correcting wind tunnel data for wall interference is a critical part of relating the acquired data to a free-air condition. Accurately determining and correcting for the interference caused by the presence of boundaries in wind tunnels can be difficult especially for facilities employing ventilated boundaries. In this work, three varying levels of ventilation at the National Transonic Facility (NTF) were modeled and calibrated with a general slotted wall (GSW) linear boundary condition to validate the computational model used to determine wall interference corrections. Free-air lift, drag, and pitching moment coefficient predictions were compared for a range of lift production and Mach conditions to determine the uncertainty in the corrections process and the expected domain of applicability. Exploiting a previously designed statistical validation method, this effort accomplishes the extension of a calibration and validation for a boundary pressure wall interference corrections method. The foundational calibration and validation work was based on blockage interference only, while this present work extends the assessment of the method to encompass blockage and lift interference production. The validation method involves the establishment of independent cases that are then compared to rigorously determine the degree to which the correction method can converge free-air solutions for differing interference fields. The process involved first establishing an empty-tunnel calibration to gain both a centerline Mach profile of the facility at various ventilation settings, and to gain a baseline wall pressure signature undisturbed by a test article. The wall boundary condition parameters were then calibrated with a blockage and lift interference producing test article, and final corrected performance coefficients were compared for varying test section ventilated configurations to validate the corrections process and assess its domain of applicability. During the validation process discrimination between homogeneous and discrete implementations of the boundary condition was accomplished and final results indicated comparative strength in the discrete implementation's ability to capture experimental flow physics. Final results indicate that a discrete implementation of the General Slotted Wall boundary condition is effective in significantly reducing variations caused by differing interference fields. Corrections performed with the discrete implementation of the boundary condition collapse differing measurements of lift coefficient to within 0.0027, drag coefficient to within 0.0002, and pitching moment coefficient to within 0.0020. / Doctor of Philosophy / The purpose of conducting experimental tests in wind tunnels is often to acquire a quantitative measure of test article aerodynamic characteristics in such a way that those specific characteristics can be accurately translated into performance characteristics of the real vehicle that the test article intends to simulate. The difficulty in accurately simulating the real flow problem may not be readily apparent, but scientists and engineers have been working to improve this desired equivalence for the better part of the last half-century. The primary aspects of experimental aerodynamics simulation that present difficulty in attaining equivalence are: geometric fidelity, accurate scaling, and accounting for the presence of walls. The problem of scaling has been largely addressed by adequately matching conditions of similarity like compressibility (Mach number), and viscous effects (Reynolds number). However, accounting for the presence of walls in the experimental setup has presented ongoing challenges for ventilated boundaries; these challenges include difficulties in the correction process, but also extend into the determination of correction uncertainties. Exploiting a previously designed statistical validation method, this effort accomplishes the extension of a calibration and validation effort for a boundary pressure wall interference corrections method. The foundational calibration and validation work was based on blockage interference only, while this present work extends the assessment of the method to encompass blockage and lift interference production. The validation method involves the establishment of independent cases that are then compared to rigorously determine the degree to with the correction method can converge free-air solutions for differing interference scenarios. The process involved first establishing an empty-tunnel calibration to gain both a centerline Mach profile of the facility at various ventilation settings, and to gain a baseline wall pressure signature undisturbed by a test article. The wall boundary condition parameters were then calibrated with a blockage and lift interference producing test article, and final corrected performance coefficients were compared for varying test section ventilated configurations to validate the corrections process and assess its domain of applicability. During the validation process discrimination between homogeneous and discrete implementations of the boundary condition was accomplished and final results indicated comparative strength in the discrete implementation's ability to capture experimental flow physics. Final results indicate that a discrete implementation of the General Slotted Wall boundary condition is effective in significantly reducing variations caused by differing interference fields. Corrections performed with the discrete implementation of the boundary condition collapse differing measurements of lift coefficient to within 0.0027, drag coefficient to within 0.0002, and pitching moment coefficient to within 0.0020.
47

Desenvolvimento de um sistema de aumento de estabilidade longitudinal de uma aeronave com enflechamento negativo e canard, com ensaios em túnel de vento / Development of a longitudinal stability augmentation system of a forward swept wing and canard airplane, with wind tunnel testing

Pereira, Natanael de Carvalho 19 August 2005 (has links)
As pesquisas modernas em aeronáutica envolvem a expansão dos envelopes de vôo, como resultado do desejo de melhorar a manobrabilidade e controlabilidade em operações táticas, e melhorar a segurança do vôo. Esses objetivos podem ser alcançados através do desenvolvimento de sistemas automáticos de controle de vôo. Os sistemas de controle aplicados a aeronaves podem ser desenvolvidos e simulados através de métodos computacionais. No entanto, existem imperfeições na simulação computacional por não se conseguir reproduzir algumas características do vôo real ou devido a simplificações no modelo matemático da aeronave. Desta forma, a construção de um modelo físico de uma aeronave em escala reduzida e a implementação de um controlador a este modelo, torna-se uma ferramenta bastante importante para validar resultados teóricos e métodos computacionais. Os custos associados a estes testes são geralmente muito menores que aqueles dos ensaios em vôo e com maior flexibilidade de instrumentação. Este trabalho descreve a construção de um modelo de aeronave, baseado no X-29, o desenvolvimento de um mecanismo de fixação do modelo ao túnel de vento, tipo rótula, e a implementação de um sistema de aumento de estabilidade longitudinal, através de um sistema de controle automático. O modelo físico possui uma configuração de asa com enflechamento negativo e canard, e que tende a ser inerentemente instável, sendo necessário o auxílio de um sistema de aumento de estabilidade. Testes de estabilidade dinâmica em arfagem foram realizados no túnel de vento em diferentes posições do centro de gravidade. Os parâmetros de estabilidade foram registrados e analisados através de uma curva de ajuste exponencial. / Modern aeronautical research involves flight envelope expansion as the result of a desire for improvement in tactical operation handling qualities and improvement in flight safety. These objectives can be achieved through the development of automatic flight control systems. Aircraft flight control systems can be developed and simulated through computational methods. However, there are imperfections in the computational simulation of flight dynamics due to the difficulty in reproducing real flight conditions or due simplifications in the aircraft mathematical model. The construction of a reduced scale physical aircraft model and the implementation of a controller is a very valuable tool to validate theoretical results and computational methods. The costs associated with these tests are usually much smaller than those associated with full scale flight testing and may offer greater flexibility for instrumentation. The present work describes the construction of an airplane model, based on the X-29, the development of a wind tunnel gimbal type support and the implementation of a longitudinal stability augmentation system using automatic flight control. The model configuration has forward swept wings and canard with a tendency to be inherently unstable and, thus, requiring a stability augmentation system. Pitching dynamic stability tests where conducted in a wind tunnel in different center of gravity positions. Stability parameters were acquired and analyzed by exponential fit curve.
48

Aeroelastic Concepts for Flexible Aircraft Structures

Heinze, Sebastian January 2007 (has links)
In this thesis, aeroelastic concepts for increased aircraft performance are developed and evaluated. Active aeroelastic concepts are in focus as well as robust analysis concepts aiming at efficient analysis using numerical models with uncertain or varying model parameters. The thesis presents different approaches for exploitation of fluid-structure interaction of active aeroelastic structures. First, a high aspect ratio wing in wind tunnel testing conditions is considered. The wing was developed within the European research project \textit{Active Aeroelastic Aircraft Structures} and used to demonstrate how structural flexibility can be exploited by using multiple control surfaces such that the deformed wing shape gives minimum drag for different flight conditions. Two different drag minimization studies are presented, one aiming at reduced induced drag based on numerical optimization techniques, another one aiming at reduced measured total drag using real-time optimization in the wind tunnel experiment. The same wing is also used for demonstration of an active concept for gust load alleviation using a piezoelectric tab. In all studies on the high aspect ratio wing, it is demonstrated that structural flexibility can be exploited to increase aircraft performance. Other studies in this thesis investigate the applicability of robust control tools for flutter analysis considering model uncertainty and variation. First, different techniques for taking large structural variations into account are evaluated. Next, a high-fidelity numerical model of an aircraft with a variable amount of fuel is considered, and robust analysis is applied to find the worst-case fuel configuration. Finally, a study investigating the influence of uncertain external stores aerodynamics is presented. Overall, the robust approach is shown to be capable of treating large structural variations as well as modeling uncertainties to compute worst-case configurations and flutter boundaries. / QC 20100713
49

Aerodynamic Modeling of Post-Stall and Spin Dynamics of Large Transport Airplanes

Murch, Austin Matthew 08 1900 (has links)
This work addressed aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport aircraft. This was accomplished by applying historically successful modeling methods used on high-performance military aircraft to a transport configuration. The overall research approach involved integrating forced oscillation and rotary balance wind tunnel data into an aerodynamic model using several methods of blending these data. The complete aerodynamic model was integrated into a six degree-of-freedom simulation. Experimental data from free-spin wind tunnel testing was used to validate the aerodynamic modeling methods by comparing aerodynamic force and moment coefficients and also to validate the simulation performance by comparing spin mode characteristics and time histories. The aerodynamic model prediction of spin dynamics was generally very good using all of the blending methods studied. In addition, key spin mode characteristics were predicted with a high degree of accuracy. Overall, using the Hybrid Kalviste method of blending forced oscillation and rotary balance data produced the closest match to the free-spin data when comparing aerodynamic coefficients and spin mode characteristics. Several issues were encountered with the blending methods that were exacerbated by nonlinearities and asymmetries in the dynamic aerodynamic data. A new method of looking up dynamic aerodynamic data was proposed to address shortcomings in the blending methods and recommendations were provided on addressing issues with the dynamic aerodynamic data.
50

Desenvolvimento de um sistema de aumento de estabilidade longitudinal de uma aeronave com enflechamento negativo e canard, com ensaios em túnel de vento / Development of a longitudinal stability augmentation system of a forward swept wing and canard airplane, with wind tunnel testing

Natanael de Carvalho Pereira 19 August 2005 (has links)
As pesquisas modernas em aeronáutica envolvem a expansão dos envelopes de vôo, como resultado do desejo de melhorar a manobrabilidade e controlabilidade em operações táticas, e melhorar a segurança do vôo. Esses objetivos podem ser alcançados através do desenvolvimento de sistemas automáticos de controle de vôo. Os sistemas de controle aplicados a aeronaves podem ser desenvolvidos e simulados através de métodos computacionais. No entanto, existem imperfeições na simulação computacional por não se conseguir reproduzir algumas características do vôo real ou devido a simplificações no modelo matemático da aeronave. Desta forma, a construção de um modelo físico de uma aeronave em escala reduzida e a implementação de um controlador a este modelo, torna-se uma ferramenta bastante importante para validar resultados teóricos e métodos computacionais. Os custos associados a estes testes são geralmente muito menores que aqueles dos ensaios em vôo e com maior flexibilidade de instrumentação. Este trabalho descreve a construção de um modelo de aeronave, baseado no X-29, o desenvolvimento de um mecanismo de fixação do modelo ao túnel de vento, tipo rótula, e a implementação de um sistema de aumento de estabilidade longitudinal, através de um sistema de controle automático. O modelo físico possui uma configuração de asa com enflechamento negativo e canard, e que tende a ser inerentemente instável, sendo necessário o auxílio de um sistema de aumento de estabilidade. Testes de estabilidade dinâmica em arfagem foram realizados no túnel de vento em diferentes posições do centro de gravidade. Os parâmetros de estabilidade foram registrados e analisados através de uma curva de ajuste exponencial. / Modern aeronautical research involves flight envelope expansion as the result of a desire for improvement in tactical operation handling qualities and improvement in flight safety. These objectives can be achieved through the development of automatic flight control systems. Aircraft flight control systems can be developed and simulated through computational methods. However, there are imperfections in the computational simulation of flight dynamics due to the difficulty in reproducing real flight conditions or due simplifications in the aircraft mathematical model. The construction of a reduced scale physical aircraft model and the implementation of a controller is a very valuable tool to validate theoretical results and computational methods. The costs associated with these tests are usually much smaller than those associated with full scale flight testing and may offer greater flexibility for instrumentation. The present work describes the construction of an airplane model, based on the X-29, the development of a wind tunnel gimbal type support and the implementation of a longitudinal stability augmentation system using automatic flight control. The model configuration has forward swept wings and canard with a tendency to be inherently unstable and, thus, requiring a stability augmentation system. Pitching dynamic stability tests where conducted in a wind tunnel in different center of gravity positions. Stability parameters were acquired and analyzed by exponential fit curve.

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