O objetivo desta pesquisa é o estudo do uso potencial de multi-winglets adaptativas para obter reduções no arrasto induzido através da variação do diedro das winglets. Os vórtices gerados nas pontas das asas são um produto inevitável da presença da sustentação, ou seja, é um custo a pagar pela força que mantém as aeronaves no ar. Diferentes estudos têm demonstrado que o escoamento presente nas pontas das asas pode ser redirecionado usando pequenas superfícies aerodinâmicas reduzindo assim o arrasto induzido. O modelo testado era constituído por uma asa retangular construída a partir de um perfil NACA 653 - 018 dotado de três winglets tipo \"tip-sails\", que são pequenas asas sem enflechamento ao 25% da corda. Os testes realizados foram para um regime de Número de Reynolds de 357.000. Os resultados foram analisados através da análise da sustentação, arrasto e mapeamento da esteira através da técnica de anemometria de fio quente. / The aim of this research is the study of the potential use of adaptive multi-winglets to reduce induced drag through variations of winglet cant angles. The vortices generated at the wing tips are an inevitable product of the presence of lift, that is, they represent the price paid for the presence for the force that keeps the aircraft in the air. Different studies have shown that the flow over the wing-tip can be redirected using small aerodynamics surfaces, thereby reducing the induced drag. The model tested is composed of a rectangular wing using a NACA 653 - 018 profile with three winglets called \"tip-sails\", which are small wings without sweep at 25% chord. The tests were made at a Reynolds number of 350,000. The results are analyzed in terms of lift and drag and mapping of the wake using hot wire anemometry techniques.

Reduções no arrasto de uma aeronave, beneficiam a performance e, reduzem a potência necessária. A componente do arrasto que oferece grande potencial, é o arrasto induzido, que varia de 30% à 50% do arrasto total. Este pode ser diminuído através de modificações nas pontas de asa. Alguns modelos, deslocam os vórtices da ponta de asa para fora, diminuindo o arrasto induzido. Outros modelos, aproveitam o fluxo em espiral nesta região, para produzirem uma tração, reduzindo o arrasto total, como as \"winglets\". Tratando-se de aviões agrícolas, que efetuam a deposição de defensivos sobre plantações em vôos rasantes, deslocamentos do vórtice são fundamentais para o aumento da eficiência do processo de pulverização. Este trabalho estudou, através de ensaios em túnel de vento, variações nas características aerodinâmicas de uma asa impostas por modificações em suas pontas. As pontas ensaiadas foram: \'delta tip\', \"winglet\" e Hoerner. Para aproximar os ensaios da realidade operacional, adicionou-se uma placa plana, paralela ao fluxo, simulando o efeito solo que ocorre no vôo rasante, durante a \"passagem\". Efetuou-se também, visualizações de fluxo para cada configuração. A ponta tipo \"Hoerner\" apresentou maior beneficio aerodinâmico e estrutural, mas não é adequada ao serviço agrícola por deslocar o vórtice para baixo, prejudicando a deposição. A \'delta tip\' possui rendimento menor porém, o vórtice melhor posicionado. Já a asa com \"winglet\", proporciona beneficio aerodinâmico modesto, excelente posicionamento do vórtice mas, prejuízo estrutural. / An airplane\'s drag reductions can improve performance and reduce the required power. The induced drag is the component which, if reduced, offers better results, because it is responsible from 30% to 50% of total drag. Such reductions in drag can be achieved through modifications of the wing tips. Some models displace wing tip vortices outwards diminishing the induced drag. Others, like the \'\'winglets\'\', make good use of the spiral draught on this portion of the wing, producing traction and reducing the total drag. Concerning agricultural airplanes, wing tip vortex position is really important while spreading products over a plantation. In this work, wind tunnel tests were made in order to find a better wing tip among the folowing types for this use: the delta tip, \"winglet\" and \"Hoerner\". The \'\'Hoerner\'\' tip was better for total drag reduction, but not good with reference to vortex position. The delta tip gave low improvement on aerodynamic characteristics, but a good vortiex position. The \"winglet\" tip had a better vortex position, but caused an undesirable result with reference to the wing root bending moment.

O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.

O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.

Over the last forty or so years interest in the study of wing-tip vortices has increased, primarily due to the introduction of larger passenger aircraft and their subsequent interaction with smaller aircraft. The vortices generated by these larger aircraft present a problem in two main areas; the wake hazard problem, where other aircraft can be subjected to the large tangential velocities of the vortex, and the interaction with ground based features of vortices created during landing and take-off. The first of these is particularly dangerous close to the ground when aircraft are in a high lift configuration at take-off and landing. As the vortices effectively scale with aircraft wing span, significant encounters between large vortices and smaller aircraft have been documented over the years. An example of one such documented wake vortex interaction incident can be found in Ogawa. In this study, the system of vortices are described as classical Batchelor vortices (or linear superpositions thereof) which are then subjected to small perturbations. By discretising the domain and solving for the eigenvalues of the system it is possible to ascertain the stability characteristics of the flow as a function of the system parameters which include the axial wave-number, the spacing of the vortices, their cross-flow decay rate and their axial strength. We first consider the inviscid instability of multiple tip vortices, an approximation which is valid in the limit of large Reynolds numbers. In this limit the stability of the flow is dominated by the axial component of the basic vortex flow. The governing equations of continuity and momentum are reduced to a second order partial differential equation (PDE). This equation is solved numerically to determine which vortex configurations produce the greatest instability growth rate. These results are extended to consider the effect of compressibility on the inviscid instability. Finally we consider the effects of viscosity on the stability of the full Batchelor similarity solution which results in a second order PDE in four dependent variables. The stability equations are solved both globally (for the entire eigenspectra) and locally (for a single eigenvalue in a pre-determined region) using codes that run in both serial and parallel form. The numerical methods are based on pseudospectral discretisation (Chebyshev polynomials for Cartesian and radial directions and Fourier for azimuthal) in the global scheme, the eigenvalues being recovered either with a QZ algorithm or a shift-and-invert Arnoldi algorithm. For the local scheme, fourth order centred finite-diffences are used in conjunction with an iterative eigenvalue recovery method. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1383207 / Thesis (Ph.D.) - University of Adelaide, School of Mathematical Sciences, 2010

Over the last forty or so years interest in the study of wing-tip vortices has increased, primarily due to the introduction of larger passenger aircraft and their subsequent interaction with smaller aircraft. The vortices generated by these larger aircraft present a problem in two main areas; the wake hazard problem, where other aircraft can be subjected to the large tangential velocities of the vortex, and the interaction with ground based features of vortices created during landing and take-off. The first of these is particularly dangerous close to the ground when aircraft are in a high lift configuration at take-off and landing. As the vortices effectively scale with aircraft wing span, significant encounters between large vortices and smaller aircraft have been documented over the years. An example of one such documented wake vortex interaction incident can be found in Ogawa. In this study, the system of vortices are described as classical Batchelor vortices (or linear superpositions thereof) which are then subjected to small perturbations. By discretising the domain and solving for the eigenvalues of the system it is possible to ascertain the stability characteristics of the flow as a function of the system parameters which include the axial wave-number, the spacing of the vortices, their cross-flow decay rate and their axial strength. We first consider the inviscid instability of multiple tip vortices, an approximation which is valid in the limit of large Reynolds numbers. In this limit the stability of the flow is dominated by the axial component of the basic vortex flow. The governing equations of continuity and momentum are reduced to a second order partial differential equation (PDE). This equation is solved numerically to determine which vortex configurations produce the greatest instability growth rate. These results are extended to consider the effect of compressibility on the inviscid instability. Finally we consider the effects of viscosity on the stability of the full Batchelor similarity solution which results in a second order PDE in four dependent variables. The stability equations are solved both globally (for the entire eigenspectra) and locally (for a single eigenvalue in a pre-determined region) using codes that run in both serial and parallel form. The numerical methods are based on pseudospectral discretisation (Chebyshev polynomials for Cartesian and radial directions and Fourier for azimuthal) in the global scheme, the eigenvalues being recovered either with a QZ algorithm or a shift-and-invert Arnoldi algorithm. For the local scheme, fourth order centred finite-diffences are used in conjunction with an iterative eigenvalue recovery method. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1383207 / Thesis (Ph.D.) - University of Adelaide, School of Mathematical Sciences, 2010

Reduções no arrasto de uma aeronave, beneficiam a performance e, reduzem a potência necessária. A componente do arrasto que oferece grande potencial, é o arrasto induzido, que varia de 30% à 50% do arrasto total. Este pode ser diminuído através de modificações nas pontas de asa. Alguns modelos, deslocam os vórtices da ponta de asa para fora, diminuindo o arrasto induzido. Outros modelos, aproveitam o fluxo em espiral nesta região, para produzirem uma tração, reduzindo o arrasto total, como as \"winglets\". Tratando-se de aviões agrícolas, que efetuam a deposição de defensivos sobre plantações em vôos rasantes, deslocamentos do vórtice são fundamentais para o aumento da eficiência do processo de pulverização. Este trabalho estudou, através de ensaios em túnel de vento, variações nas características aerodinâmicas de uma asa impostas por modificações em suas pontas. As pontas ensaiadas foram: \'delta tip\', \"winglet\" e Hoerner. Para aproximar os ensaios da realidade operacional, adicionou-se uma placa plana, paralela ao fluxo, simulando o efeito solo que ocorre no vôo rasante, durante a \"passagem\". Efetuou-se também, visualizações de fluxo para cada configuração. A ponta tipo \"Hoerner\" apresentou maior beneficio aerodinâmico e estrutural, mas não é adequada ao serviço agrícola por deslocar o vórtice para baixo, prejudicando a deposição. A \'delta tip\' possui rendimento menor porém, o vórtice melhor posicionado. Já a asa com \"winglet\", proporciona beneficio aerodinâmico modesto, excelente posicionamento do vórtice mas, prejuízo estrutural. / An airplane\'s drag reductions can improve performance and reduce the required power. The induced drag is the component which, if reduced, offers better results, because it is responsible from 30% to 50% of total drag. Such reductions in drag can be achieved through modifications of the wing tips. Some models displace wing tip vortices outwards diminishing the induced drag. Others, like the \'\'winglets\'\', make good use of the spiral draught on this portion of the wing, producing traction and reducing the total drag. Concerning agricultural airplanes, wing tip vortex position is really important while spreading products over a plantation. In this work, wind tunnel tests were made in order to find a better wing tip among the folowing types for this use: the delta tip, \"winglet\" and \"Hoerner\". The \'\'Hoerner\'\' tip was better for total drag reduction, but not good with reference to vortex position. The delta tip gave low improvement on aerodynamic characteristics, but a good vortiex position. The \"winglet\" tip had a better vortex position, but caused an undesirable result with reference to the wing root bending moment.

O objetivo desta pesquisa é o estudo do uso potencial de multi-winglets adaptativas para obter reduções no arrasto induzido através da variação do diedro das winglets. Os vórtices gerados nas pontas das asas são um produto inevitável da presença da sustentação, ou seja, é um custo a pagar pela força que mantém as aeronaves no ar. Diferentes estudos têm demonstrado que o escoamento presente nas pontas das asas pode ser redirecionado usando pequenas superfícies aerodinâmicas reduzindo assim o arrasto induzido. O modelo testado era constituído por uma asa retangular construída a partir de um perfil NACA 653 - 018 dotado de três winglets tipo \"tip-sails\", que são pequenas asas sem enflechamento ao 25% da corda. Os testes realizados foram para um regime de Número de Reynolds de 357.000. Os resultados foram analisados através da análise da sustentação, arrasto e mapeamento da esteira através da técnica de anemometria de fio quente. / The aim of this research is the study of the potential use of adaptive multi-winglets to reduce induced drag through variations of winglet cant angles. The vortices generated at the wing tips are an inevitable product of the presence of lift, that is, they represent the price paid for the presence for the force that keeps the aircraft in the air. Different studies have shown that the flow over the wing-tip can be redirected using small aerodynamics surfaces, thereby reducing the induced drag. The model tested is composed of a rectangular wing using a NACA 653 - 018 profile with three winglets called \"tip-sails\", which are small wings without sweep at 25% chord. The tests were made at a Reynolds number of 350,000. The results are analyzed in terms of lift and drag and mapping of the wake using hot wire anemometry techniques.

The primary purpose of this thesis is to quantify the effects of RANS turbulence modeling on the resolution of free shear vortical flows. The simulation of aerodynamic wing-tip vortices is used as a test bed. The primary configuration is flow over an isolated finite wing with aspect ratio, , and Reynolds number, . Tip-vortex velocity profiles, vortex core and wake turbulence levels, and Reynolds stresses are compared with wind tunnel measurements. Three turbulence models for RANS closure are tested: the Lumley, Reece, and Rodi full Reynolds stress transport model and the Sparlart-Allmaras model with and without a proposed modification. The main finding is that simulations with the full Reynolds stress transport model show remarkable mean flow agreement in the vortex and wake due to the proper prediction of a laminar vortex core. Simulations with the Spalart-Allmaras model did not indicate a laminar core and predicted over-diffusion of the tip-vortex. Secondary investigations in this work include the study of wall boundary layer treatment and simulating the wake-age of an isolated rotorcraft in hover using a steady-state RANS solver. By comparing skin friction plots over the NACA 0012 airfoil, it is shown that wall functions are most effective in the trailing edge half of the airfoil, while high velocity gradient and curvature of the leading edge make them more vulnerable to discrepancies. The rotorcraft simulation uses the modified Spalart-Allmaras turbulence model and shows proper, qualitative, resolution of the interaction between the vortex sheet and the tip vortex. / Master of Science

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