Dissertations / Theses on the topic 'Wind tunnel balance'

All the operational and measurement systems of Ankara Wind Tunnel was modified to operate automatically under the control of a central computer system programmed using the Lab View programming language. A cruciform air-to-air missile with triangular canard control and a trapezoidal wing model was tested by a 35mm diameter internal balance at Mach 0.2 and data was compared with the test data of the same model&rsquo
s test that was performed at NASA Langley Research Center.

In recent years, especially in the crowded city-centers where land prizes have become extremely high, tall buildings with more than 30 floors have started to be designed and constructed in Turkey. On the other hand, the technical improvements have provided the opportunity of design and construction of more slender structures which are influenced by the wind actions more. If the building is flexible, wind can interact with it so the wind induced oscillations can be significantly magnified. In order to analyze the response of such buildings under wind effects, wind tunnel tests are accepted to be the most powerful tool all over the world. In this study, a series of tests were performed in Ankara Wind Tunnel on a model building in the shape of a rectangular prism. For the similitude of flow conditions, passive devices were designed. The response of the model building was measured through a high frequency base balance which was designed specifically for this case study. Through the tests, the effects of turbulence intensity, vortex shedding and wind angle of attack on the response of the building were questioned. Finally, the results were compared with the results of various technical specifications about wind.

Although small scale magnetic suspension and balance systems (MSBSs) for wind tunnel use have been in existence for many years, they have not found general application in the production testing of flight vehicles. One reason for this is thought to lie in the relatively limited range of attitudes over which a wind tunnel model may be suspended. This text reports on the modifications made to an existing small MSBS at Southampton University to permit the suspension and control of axisymmetric models over an angle of attack range from less than zero degrees to over ninety degrees. Previous work had shown that the existing arrangement of ten electromagnets was unable to generate one of the force components necessary for control at the extreme attitudes. Examination of possible solutions has resulted in a simple alteration which rectifies this deficiency. To generate the feedback signals essential to control the magnetically suspended model, an optical position sensing system using collimated beams of laser light illuminating photodiode arrays has been installed and tested. An analytical basis has been developed for distributing the demands for force and moment needed for model stabilisation amongst the electromagnets and over the full attitude range. This has been implemented by an MSBS control program able to continually adjust the distribution for the instantaneous incidence in accordance with pre-scheduled data. Results presented demonstrate rotations of models from nought to ninety degrees at rates of change up to ninety degrees per second, with pitching rates rising to several hundred degrees per second in response to step-change demands. A study of a design for a large MSBS suggests that such a system could be given the capability to control a model in six degrees of freedom over an unlimited angle of attack range.

Force and moment balances have proved to be essential in the measurement and calculation of aerodynamic properties during wind tunnel testing. With the recent advancements of technology, new fiber optic sensors have been designed to replace the conventional foil strain gage sensors commonly found on balances, thereby offering several distinct advantages. The use of fiber optic sensors on a balance brings with it some potential advantages over conventional strain gage balances including increased resolution and accuracy, insensitivity to electromagnetic interference, and the capability of use at high temperatures. By using the fiber optic sensors, some of the limitations of the conventional balance can be overcome, leading to a better overall balance design.

This thesis considers an initial trial application of new fiber optic sensors on a conventional, six-component sting balance while retaining the original foil strain gage sensors for comparison. Tests were conducted with a blunt, 10º half-angle cone model in the Virginia Tech 9x9 inch Supersonic Wind Tunnel at Mach 2.4 with a total pressure of 48 psia and ambient total temperature of 25.3ºC. Results showed a close comparison between the foil strain gages and the fiber optic sensor measurements, which were set up to measure the normal force and pitching moment on the blunt cone model. A Finite Element Model (FEM) of the sting balance was produced in order to determine the best locations for the fiber optic sensors on the sting balance. Computational Fluid Dynamics (CFD) was also used in order to predict and compare the results acquired from all of the sensors.
Master of Science

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2003.
Thesis advisor(s): E. Roberts Wood, Richard M. Howard. Includes bibliographical references (p. 53-54). Also available online.

The subject of this experimental investigation is to measure the dynamic stability derivatives in roll plane for an oscillating combat aircraft model by using forced oscillation technique. In forced oscillation technique the model is forced to oscillate around the center of gravity according to a harmonic motion of small amplitude and low frequency. The aerodynamic reactions are measured by an internal balance placed inside the model. The thesis presents a brief description of the test rig and the measurement system. The theory of dynamic stability derivatives and forced oscillation technique are also explained. The data is collected and analyzed by using a data acquisition system written with under the Labview programming language. Systematic analysis of the static and dynamic tests results and effect of various parameters (angle of attack, sideslip angle, oscillation frequency and amplitude, wind velocity) on these results are presented. Comparison of the present results with previous results obtained in other test facilities is also given. Design and manufacture process of a new angle of attack mechanism is also given in this thesis.

Tato práce se zabývá měřením aerodynamických charakteristik modelu závodního vozu Formula SAE v aerodynamickém tunelu, v měřítku 1:4. V první části je představen projekt Formula SAE a popsána role aerodynamiky v rámci této soutěže. Následuje přehled teoretického pozadí, které je relevantní k provedenému experimentu. Ve druhé části práce je popsán samotný experiment a prezentovány jeho výsledky. Součástí je návrh, výroba a kalibrace šestikomponentní tenzometrické váhy pro měření aerodynamického zatížení. Testy v aerodynamickém tunelu byly provedeny ve čtyřech konfiguracích, aby bylo možné určit vliv přítlačných křídel a podlahy s difuzorem na výsledné aerodynamické charakteristiky vozu.

In this thesis, techniques for testing aircraft models in ground effect in a low speed wind tunnel are investigated. Although these types of tests have been done before, the current study is unique in that forces are measured with an overhead balance instead of an internal balance. This has the advantage that the types of models that are difficult to mount on a sting with an internal balance, can often be mounted with a strut protruding from the top of the model. Positioning a sting-mounted model close to the ground at a high angle-of-attack is also usually difficult if not impossible. Finally, drag measurements are often more accurate when measured with an overhead balance rather than with an internal sting-type balance. The disadvantages associated with this method of testing are identified and solutions suggested. These include accurate moment transfers and correcting for support tares and interference. The thesis also investigates general procedures associated with ground effect testing such as proper boundary corrections and the necessity of a rolling floor. A simplified preliminary test series was performed in order to identify shortcomings in the existing equipment and procedures. This series is explained in Chapter 2. Chapter 4 and 5 describe changes made to the existing equipment following this test series. These include a novel telescopic fairing to shroud the mounting strut and an internal pitching mechanism. The correction techniques and general theory are summarised in Chapter 3. The author concludes in Chapter 6 that with the application of the techniques described in this thesis, the test engineer should be able to obtain accurate and reliable data from most aircraft configurations. Additional suggestions for testing models in ground effect are also given in this chapter. Finally, a few shortcomings that still need to be investigated are mentioned at the end of Chapter 6. AFRIKAANS : Hierdie verhandeling ondersoek tegnieke om vliegtuigmodelle in grondeffek in 'n laespoed-windtonnel te toets. Alhoewel hierdie tipe van toetse al voorheen gedoen is, is die huidige studie uniek deurdat 'n oorhoofse balans eerder as 'n interne balans gebruik word. Die voordeel hiervan is dat modelle wat moeilik op 'n naald- of "sting"-balans monteer kan word, baie keer makliker monteer kan word met 'n stang wat deur die bokant van die model steek. Posisioneering van 'n naald-gemonteerde model naby aan die vloer van die tonnel by hoe invalshoeke is gewoonlik ook baie moeilik indien nie onmoontlik nie. Laastens is sleurkrag-metings wat met 'n oorhoofse balans gemeet is gewoonlik meer akkuraat as sleurkrag-metings wat met 'n interne naald-tipe balans gedoen is. Die nadele wat met hierdie toetsmetode geassosieer kan word, word geïdentifiseer en moontlike oplossing word voorgestel. Hierdie sluit die berekening in van akkurate moment-transformasies en monteersleureffekte en -steurings. Die verhandeling ondersoek ook algemene prosedures wat met grondeffektoetse geassosieer kan word, byvoorbeeld akkurate wandkorreksies en die nodigheid van die rolvloer. 'n Vereenvoudigde vooraf-toetsreeks was uitgevoer om moontlike tekortkominge in die bestaande toerusting en prosedures te identifiseer. Hierdie toetsreeks word in Hoofstuk 2 bespreek. Hoofstuk 4 en 5 verduidelik die veranderinge wat aan die bestaande toerusting gemaak is na aanleidng van hierdie toetsreeks. Hierdie veranderinge sluit 'n teleskopiese windskerm in om die monteerstang te isoleer van die wind, sowel as 'n interne heimeganisme om die invalshoek van die model te verstel. Die korreksieprosedures en algemene teorie word in Hoofstuk 3 opgesom. Die outeur se gevolgtekking in Hoofstuk 6 stel dat die toetsingenieur, met behulp van die gebruik van die tegnieke in hierdie verhandeling beskryf, in staat behoort te wees om betroubare metings te kan neem van meeste vliegtuigkonfigurasies. Verdere voorstelle vir die toets van modelle in grondeffek word ook in hierdie hoofstuk gemaak. Uiteindelik word 'n paar tekortkominge genoem wat moontlik in 'n toekomstige studie ondersoek kan word.
Dissertation (MEng)--University of Pretoria, 1999.
Mechanical and Aeronautical Engineering
unrestricted

It is important to keep an overhead power line within rated operating conditions. Thus,an accurate prediction of the conductor's thermal and electrical behavior leads to an increasein reliability and eciency. Under DLR operation, the current rating is adjustedbased on ambient weather and solar conditions to allow for dynamic line loading. Therating adjustment takes into account the cooling mechanisms acting on the conductor. Inthis thesis, cooling by means of convective heat transfer is studied based on wind tunnelexperimental measurements of three dierent conductor samples. Convection contributesto most of the cooling; however, it is aected by wind speed and direction. Two angle ofattacks were studied (40 and 90), where perpendicular ow was found to result in bettercooling. The location of boundary layer separation highly aects the surface distribution ofcooling, which is non-uniform. Oblique wind ow results in reduction in overall cooling dueto earlier boundary layer separation. Finally, the surface average convective heat transfercoecient correlates non-linearly with the Reynolds number, where higher wind speeds andlarger conductor diameters can lead to signicant improvements in cooling while keepingrelatively low current densities. The existing standards of IEEE and CIGRE were found tooverestimate the eect of convective cooling for the specic experimental cases.
Det är viktigt att hålla en kraftöverföringsledning inom nominella driftsförhållanden.Således leder en korrekt förutsägelse av ledarens termiska och elektriska beteende till en ökad tillförlitlighet och effektivitet. Under DLR-drift justeras nuvärdet baserat på omgivande väder och solförhållanden för att möjliggöra dynamisk belastning. Klassificeringsjusteringen tar hänsyn till de kylmekanismer som verkar på ledaren. I denna avhandling studeras kylning med hjälp av konvektiv värmeöverföring baserat på provning av vindtunnel av tre olika ledartyper. Konvektion bidrar till det mesta av kylningen. Det påverkas dock av vindhastighet och riktning. Två angreppsvinkelar studerades (40◦ och 90◦), där vinkelrätt flöde befanns resultera i bättre kylning. Placeringen av ytskiktseparationen har stor inverkan på ytfördelningen av kylning, vilken är ojämn. Skrå vindflöde resulterar i minskning av den totala kylningen på grund av tidigare separering av gränsskiktet. Slutligen korrelerar den ytvärdesöverföringskoefficienten för ytvärdet icke-linjärt med Reynolds-talet, där högre vindhastigheter och större ledardiametrar kan leda till signifikanta förbättringar i kylning samtidigt som relativt låga strömtäthet hålls. De befintliga standarderna för IEEE och CIGRE visade sig överskatta effekten av konvektiv kylning för de specifika experimentellafallen.

The masters thesis is focused on design of the device for measurement of the aerodynamic forces and moments acting on radiators mounted in the wind tunnel test section. The thesis also includes the analysis of the aerodynamic drag which is produced by radiators and the LabView application software development.

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.

This master thesis focuses on designing of an external six-component balance. This universal concept would provide access of results from different models of wings, aircraft and automobiles with relatively small scales. This work also includes theoretical background needed in aerodynamic testing, analysis of 1D beam element model of scale and explanation of components used in scale. Lastly methods of calibration and measurement in aerodynamic tunnel are described, which can be adopted for this design to achieve the adequate level of accuracy.

Medições realizadas em edifícios altos, em escala real, têm mostrado que o carregamento devido à ação do vento pode causar importantes efeitos de torção. A atual tendência de construção de prédios com formas e sistemas estruturais mais complexos promove a acentuação das excentricidades entre o centro de massa, centro elástico e o ponto de aplicação instantânea de forças aerodinâmicas. Soma-se a isso o fato de os edifícios altos modernos estarem se tornando cada vez mais esbeltos e leves, o que baixa a velocidade (do vento) de disparo de fenômenos como galope e drapejamento torcional, fazendo com que esta velocidade se aproxime cada vez mais das velocidades do vento consideradas nos projetos. Frente a isso, os efeitos dinâmicos, tanto de flexão como de torção, induzidos pelo vento em edifícios altos representam uma importante consideração nos projetos de estruturas modernas. Os métodos analíticos para determinação da resposta de edifícios altos submetidos à ação do vento, hoje disponíveis, não levam a resultados satisfatórios em casos de geometrias não regulares, bem como não contemplam efeitos torsionais. Seu uso também não é recomendado no caso de estruturas muito flexíveis, cujo movimento afeta as forças aerodinâmicas que nelas atuam. Nessas situações, a melhor opção para os engenheiros é um estudo mais detalhado dos efeitos do vento sobre a estrutura, através de ensaios de modelos em escala reduzida em túneis de vento, que simulem as características do vento natural. O objetivo deste trabalho é o desenvolvimento de um mecanismo que permita a obtenção da resposta de edifícios altos frente à ação do vento, a partir de ensaios em túnel de vento com modelos em escala reduzida. Busca-se determinar a resposta em termos de suas componentes médias e flutuantes. Admite-se que a parcela dinâmica contempla os dois modos fundamentais de vibração livre em flexão, ortogonais entre si e aproximados de forma linear, e o primeiro modo de torção, aproximado de forma constante. As simplificações adotadas permitem que os modelos tenham baixa complexidade de projeto e construção, diminuindo, assim, o custo da modelagem e tornando o processo experimental mais ágil. Para validar os resultados obtidos com a utilização do mecanismo desenvolvido foram realizados ensaios em escala reduzida do CAARC Standard Tall Building, edifício alto tomado como padrão para calibração de técnicas de modelagem aeroelástica, no Túnel de Vento Professor Joaquim Blessmann, da Universidade Federal do Rio Grande do Sul. Os resultados obtidos foram comparados com os valores publicados por outros pesquisadores e com resultados determinados a partir de ensaios de medidas de pressões em alta freqüência. A coerência entre os valores comparados permitiu concluir que o equipamento simula satisfatoriamente o comportamento dinâmico de edifícios altos submetidos à ação do vento, mesmo perante fenômenos aeroelásticos, como a ressonância por desprendimento alternado de vórtices. A partir dos resultados verificou-se também a importância dos efeitos dinâmicos de torção induzidos pela ação do vento, e a necessidade de que sejam apropriadamente considerados nos projetos
Measurements performed in full-scale high rise buildings have shown that wind loading may cause important torsional effects. The current trend of building construction, with new shapes and complex structural systems promotes an increase in the distances (eccentricities) among the center of mass, elastic center and the instantaneous point of application of the resulting wind loads. Furthermore, modern tall buildings are becoming increasingly light and slender, diminishing the trigger wind speed of some phenomena such as galloping and torsional flutter, bringing these velocities closer to the design wind speeds. Therefore, wind induced bending and torsional dynamic effects in tall buildings play an important role in the design of modern structures. The current analytical methods for the response determination of tall buildings under wind loading do not lead to reliable results for the non regular building shapes, as well as do not consider torsional effects. Also, its use is not recommended for the case of very flexible structures, where the structure´s own motion may affect the aerodynamic forces acting on it. In these situations, the best option for engineers is a more detailed study of the wind effects, through boundary layer wind tunnels. The aim of this study is the development of a device that allows the determination of the response of tall buildings under wind loading, through wind tunnel tests with reduced scale models. The goal is the determination of the responses in terms of its mean and fluctuating components. It is assumed that the dynamic parcel contemplates the two fundamental bending modes of vibration, orthogonal and linear, as well as the torsional mode, which is assumed constant along the height. The adopted simplifications allow for a low complexity in the process of model design and construction as well as for a very low modeling cost, making more efficient the whole testing process. To validate the device, tests were performed with a reduced scale model of the CAARC Standard Tall Building, which is taken as a standard for the calibration of aeroelastic modeling techniques, in Prof. Joaquim Blessmann boundary layer wind tunnel of the Federal University of Rio Grande do Sul. The obtained results were compared with other researchers' values as well as with results obtained from pressure measurements, in a rigid model. The agreement among the compared values allows the conclusion that the device simulates satisfactorily well the dynamic behaviour of high rise buildings under wind loading, even for aeroelastic phenomena such as the resonance due to vortex shedding. It was also verified the importance of the wind induced torsional effects and the need for its proper consideration in the design process.

Orientador: Lucila Chebel Labaki
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: A ventilação natural é uma das estratégias mais adequadas para o resfriamento passivo dos edifícios e para a manutenção da qualidade do ar. Uma das alternativas existentes para se alcançar tal proposição é a utilização de torres de vento situadas acima do nível da cobertura, as quais podem funcionar como captadores ou extratores de ar. Esta pesquisa tem como objetivo geral avaliar quatro tipos de torres, atuando como captadores: a unidirecional, com uma abertura para a entrada de vento, em locais onde o vento se movimenta predominantemente em uma direção; a tetradirecional, com quatro aberturas; a octodirecional, com oito aberturas e a dodecadirecional, com doze aberturas; em locais em que o vento age em várias direções. Para alcançar o objetivo utilizaram-se ensaios em túnel de vento e simulações no software CFX®, os quais permitiram estudar as características técnicas das torres analisadas e seus efeitos sobre a ventilação interna do ambiente, bem como contribuir para a difusão desse sistema de ventilação no Brasil. O desenvolvimento do trabalho foi dividido nas seguintes etapas: definição das geometrias das torres; definição, construção e instrumentação das maquetes; definição dos ângulos de incidência do vento; ensaios no túnel de vento e simulações no software CFX®: velocidade e pressão. Os resultados obtidos a partir de uma série de experimentos e simulações computacionais permitiram a análise e comparação dos diversos projetos propostos, auxiliando, portanto, na determinação das configurações mais adequadas, além da verificação da compatibilidade entre os dois tipos de estudo, concluindo que as torres octodirecional e dodecadirecional são as mais eficientes, pois proporcionam maiores valores de velocidade do ar interno na maioria das posições consideradas. Desta forma, utilizando o túnel de vento e o CFX®, as análises possibilitaram desenvolver melhorias para os ambientes avaliados, no que se refere ao desempenho da ventilação. Isso proporcionará melhores taxas de conforto aos usuários da edificação, considerando todas as aberturas para permitir o fluxo do vento em qualquer situação. Ademais, podem-se verificar as distribuições das aberturas de entrada e saída mais adequadas para captação e distribuição do vento no interior dos ambientes, proporcionando melhores condições de conforto térmico
Abstract: Natural ventilation is one of the most appropriate strategies for passive cooling of buildings and the maintenance of air quality. One of the alternatives for achieving such proposal is the use of wind towers above the level of the roof, which can function as air catchers or extractors. This research aims to evaluate four types of towers, acting as air catchers: unidirectional, with an opening for the entrance of the wind, in locations where the wind moves predominantly in one direction, the tetradirectional, with four openings, the octodirectional, with eight openings and dodecadirectional, with twelve openings, in locations where the wind moves in various directions. To achieve the goal, tests in wind tunnel and simulations in CFX® software were performed, which allowed the study of the technical characteristics of the analyzed towers and their effects on the indoors ventilation, as well as the contribution to the spread of this ventilation system in Brazil. The methodology was divided into the following steps: the definition of the geometry of the towers; definition, construction and instrumentation of the models; definition of the angles of the incidence of the wind; wind tunnel tests and simulations in CFX® software: speed and pressure. The obtained results from a series of experimental and computational simulations allowed the analysis and comparison of the various proposed design configurations, helping, therefore, in determining the most appropriate settings, besides the verification of compatibility between the two types of study, concluding that the octodirectional and dodecadirectional towers are the most efficient ones , as they provide higher rate of indoor air speed in most considered positions. Thus, using the wind tunnel and CFX®, the analysis allowed the development of enhancements to the analyzed environments, concerning the performance of the ventilation. This will provide better comfort rates to the users of the building, considering all openings to allow the wind flow in any situation. Furthermore, the most suitable distribution of inlet and outlet openings for the catchment and distribution of the wind within the environments may be verified, providing better conditions of thermal comfort
Doutorado
Arquitetura e Construção
Doutor em Engenharia Civil

D. Phil.
Conventional internal wind tunnel balances are designed and constructed to accommodate foil strain gauges which measure the deformation (strain) of the material. Foil strain gauge balances are known to be affected by electromagnetic interference and temperature. These balances are expensive and their manufacture is time consuming. With an increasing demand for higher accuracy, stiffness, increased resolution and temperature compensation, current balance designs are becoming inadequate. To overcome identified balance deficiencies a research programme in the application of optical Bragg gratings to wind tunnel balances was initiated. In this programme a new concept of using optical fibre Bragg grating sensors, with the advantage of using mechanical amplification to increase sensitivity, and the implementation of temperature compensation techniques was demonstrated on a simulated two component balance.

Achieving high quality, consistency, and testing efficiency in wind tunnel tests using internal balances is accomplished through the use of new testing methods, analysis of data output, and standardized documentation of test procedures at the Texas A&M Low Speed Wind Tunnel. The wind tunnel is capable of performing internal balance testing on models that experience less than 500 pounds of normal force. Testing has shown less than a 3% mean flow variation with the sting mount installed and a turbulence intensity of less than 0.25%. Documentation of procedures and check- lists for installation of internal balance testing equipment and test execution provide higher efficiency and consistency during a test. A step-by-step examination of the data analysis routines and associated uncertainty equations show uncertainty in the force and moment coefficients for the Mark XIII internal balance to be approximately ± 0.05 and ± 0.02, respectively. Quantifying the uncertainty of the primary output parameters and showing repeatability of the data within the defined uncertainty limits achieved higher quality results.

M.Phil.
In today's world with its competitive environment there is a need to shorten product development time by using CFD (Computational Fluid Dynamics) to design an object for example a car, aeroplane or missile and to predict the forces that the wind will have on the object (design). To evaluate the correctness of the CFD results, the design or a scale model of the design must be tested in a wind tunnel by using a force balance. The wind tunnel balance is an apparatus used in the designing and testing of wings, shapes and profiles. In general a balance can be used in all aerodynamic designs to determine the forces on an object when it is moving through air. The aim of this project was to design and manufacture a three-component external balance for a low-speed wind tunnel using an axiomatic design method. It also covers the installation of the external wind tunnel balance to a wind tunnel with a computerized data acquisition capturing system, and performance evaluation of the wind tunnel balance.

D.Ing. (Mechanical Engineering)
The most common data sought during a wind tunnel test program are the forces and moments acting on an airframe, (or any other test article). The most common source of this data is the internal strain gauge balance. Balances are six degree of freedom force transducers that are required to be of small size and of high strength and stiffness. They are required to deliver the highest possible levels of accuracy and reliability. There is a focus in both the USA and in Europe to improve the performance of balances through collaborative research. This effort is aimed at materials, design, sensors, electronics calibration systems and calibration analysis methods. Recent developments in the use of statistical methods, including modern design of experiments, have resulted in improved balance calibration models. Research focus on the calibration of six component balances has moved to the determination of the uncertainty of measurements obtained in the wind tunnel. The application of conventional statistically-based approaches to the determination of the uncertainty of a balance measurement is proving problematical, and to some extent an impasse has been reached. The impasse is caused by the rapid expansion of the problem size when standard uncertainty determination approaches are used in a six-degree of freedom system that includes multiple least squares regression and iterative matrix solutions. This thesis describes how the uncertainty of loads reported by a six component balance can be obtained by applying a direct simulation of the end-to-end data flow of a balance, from calibration through to installation, using a Monte Carlo Simulation. It is postulated that knowledge of the error propagated into the test environment through the balance will influence the choice of calibration model, and that an improved model, compared to that determined by statistical methods without this knowledge, will be obtained. Statistical approaches to the determination of a balance calibration model are driven by obtaining the best curve-fit statistics possible. This is done by adding as many coefficients to the modelling polynomial as can be statistically defended. This thesis shows that the propagated error will significantly influence the choice of polynomial coefficients. In order to do this a Performance Weighted Efficiency (PWE) parameter is defined. The PWE is a combination of the curve-fit statistic, (the back calculated error for the chosen polynomial), a value representing the overall prediction interval for the model(CI_rand), and a value representing the overall total propagated uncertainty of loads reported by the installed balance...

The objective of the work in this thesis was to to equip the University’s of Beira Interior wind tunnel with a Low Reynolds Number (LRN) Propeller Performance Test Rig. This LRN condition is veri ed in small Unmanned Aerial Vehicles (UAVs) applications or in the high-altitude airships covered by the project MAAT-Multybody Advanced Airship for Transport. The design, construction and validation of an accurate measuring mechanism was conducted. The test rig was developed to collect performance data of propellers with diameter between 6 to 14 inches (approx. 0.15 to 0.40m), operating at Reynolds number between 30,000 to 300,000 (based on chord at 3=4 of the blade radius). The design chosen for the thrust balance closely resembles the T-shaped pendulum structure originally built in the University of Illinois at Urbana-Champaign (UIUC). Due to the adjustable load cell positioning, this setting allows the use of the full range of the load cell for most thrust levels in the propeller size, relative wind speed and rotation speed ranges. The test rig was completely validated and the experimental procedure was shown herein as well. Furthermore, thrust and torque characteristics of two Aeronaut Carbon Electric were measured. It was shown that as the Reynolds number increases with the increase of propeller RPM, it affects the propellers performance increasing their thrust coef cient and their ef ciency. The developed test rig can be used for several purposes, namely: the design of propellers in the UBI’s Department of Aerospace Sciences; the development UAVs, as well as the validation and improvement of numerical tools such as JBLADE.
O objetivo do trabalho levado a cabo nesta tese foi dotar o túnel de vento da Universidade da Beira Interior de um equipamento de medição de desempenho de hélices de baixo número de Reynolds. Esta condição veri ca-se em casos da aplicação em pequenos Veículos Aéreos Não Tripulados (VANTs) ou aeronaves que operem a grande altitude, como é o caso dos dirigíveis no projeto MAAT-Multybody Advanced Airship for Transport. O sistema de medição foi desenvolvido para recolher dados de desempenho de hélices com um diâmetro compreendido entre 6 e 14 polegadas (aprox. 0,15 a 0,40 m), operando num número de Reynolds compreendido entre 30.000 a 300.000 (baseado na corda a 3=4 do raio da pá). O conceito escolhido para a estrutura da balança desenvolvida para a medição da tração, consiste num pêndulo em forma de T que se assemelha ao originalmente construído na Universidade de Illinois em Urbana-Champaign (UIUC). Devido ao posicionamento ajustável de célula de carga, esta con guração permite a utilização de toda a escala da célula de carga para a maioria das condições de funcionamento das hélices propostas. A conceção, construção e validação de todo o mecanismo e procedimentos de medição são apresentados detalhadamente. Além disso, foi medido o desempenho de duas hélices da gama CAM Carbon do fabricante Aeronaut, a de duas pás 13x8 e a de três pás 12x8 . Foi demonstrado que, o aumento do número de Reynolds associado ao aumento das RPM, tem uma in uência considerável no desempenho das hélices, aumentando a sua e - ciência e coe ciente de tração. A instalação experimental desenvolvida pode ser utilizada para diversos ns, nomeadamente: o projeto de hélices no seio do Departamento de Ciências Aeroespaciais da UBI; para os trabalhos de desenvolvimento de VANTs, bem como para a validação e aperfeiçoamento de ferramentas numéricas como é o JBLADE.