Winglets being a small structure play an important role in reducing the induced drag in aircraft. Many types of winglets have been designed and their significance in reducing the drag is published. One of the main objectives of this master thesis work is to study about the winglet design and about their contribution in reducing induced drag. A brief overview of wing tip devices and their performance from the manufacturers as well as from airliner’s point of view are discussed. Moreover, the role of winglet in reducing the drag of commercial civil jet aircraft is studied and the percentage of drag reduction is calculated by a conceptual approach. A320 specifications are taken to perform induced drag reduction calculation with and without winglets. Indeed, the total drag count reduced with the help of winglets accounts for additional payload which will be an advantage for the aircraft operator. Reducing the process time in design is one of the important criteria for any field and hence automation with help of CAD tools is very significant in reducing time. This study also aims at developing an automated model for different types of winglets and wing tip devices with the help of CAD technology focused on reducing design time during the initial design process.  Knowledge based approach is used in this work and all the models are parameterized so each model could be varied with associated parameters. The generic model created would take different shapes and switches between different types of wing tip devices as per the user’s requirement with the help of available parameters. Knowledge Pattern (KP) approach is used to develop the automation process. User Defined Features (UDFs) are created for each type of winglet and tip devices. CATIA V5 R18 software is used to develop the models of winglets and tip devices.

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.

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.

This thesis discusses a comparison of the differences in aerodynamic performance of wings designed with elliptical and bell-shaped lift distributions. The method uses a Standard Cirrus sailplane wing with a lift distribution associated with the induced drag benefits of an elliptical distribution (span efficiency = 0.96) as the basis of comparison. The Standard Cirrus is a standard class sailplane with 15-meter wingspan that was designed by Schempp-Hirth in 1969. This sailplane wing was modeled and analyzed in XFLR5, then validated against existing wind tunnel airfoil data, and Standard Cirrus flight test data. The root bending moment of the baseline wing was determined and used as the primary constraint in the design of two wings with bell-shaped lift distribution. These wings were modeled in XFLR5 by adjusting chord length and geometric twist respectively, and then they were studied using fixed speed lifting line analysis. Steady state cruise conditions for the Standard Cirrus sailplane were taken from the flight test data and applied for the analysis. The wing designed with chord variation posed incompatibilities with the lifting line method. The resulting planform was strongly tapered in the wingtip region and the reference chord length there was such that the software could not solve for a Reynolds number the magnitude resulting from two-dimensional airfoil analysis. However, the wing geometry provided insight into the design aspect of wings with bell-shaped lift distribution. Using chord variation to shape the lift distribution, the wing featured a 12% increase in wingspan but a 6.5% decrease in total wetted area when compared to the baseline. The results of the analysis of the wing designed with geometric twist indicate that induced drag decreased by 5% when compared to the baseline wing. The constraint on root bending moment resulted in a 12% increase in wingspan. Wetted area also increased by 14.8% over the baseline yielding an estimated 15% increase in skin friction.

The transition of flight from manned to unmanned systems has led to new research and applications of technology within the field that, until recently, were previously thought to be unfeasible. The industry has become interested in alternative control surfaces and uses for smart materials. A Macro Fiber Composite (MFC), a smart material, takes advantage of the piezoelectric effect and provides an attractive alternative actuator to servos in the Small Unmanned Aerial Systems (SUAS) regime of flight. This research looks to take MFC actuated control surfaces one step further by pulling inspiration from and avian flight. A dual mode control surface, created by applying two sets of two MFCs to patch of carbon fiber, can mimic the tip feathers of a bird. This actuator was modeled both using Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD). Real-world static testing on a feather confirmed preliminary FEA results, and wind tunnel tests simulating assumed cruise conditions confirmed the feather would not exhibit any adverse structural behaviors, such as flutter or aeroelastic divergence. From its modeled performance on a wing using CFD, the MFC feather proved to be a success. It was able to produce a wing that, when compared to a traditional rectangular wing, yielded 73% less induced drag and generated proverse yaw. However, the MFC feathers alone, in the configuration tested, did not produce enough roll authority to feasibly control an aircraft. / Master of Science / The transition of flight from manned to unmanned systems has led to new research and applications of technology within the field that, until recently, were previously thought to be unfeasible. The industry has become interested in alternative control surfaces and uses for smart materials. A Macro Fiber Composite (MFC), a smart material, takes advantage of a specific material property and provides an attractive alternative actuator to servos in the Small Unmanned Aerial Systems (SUAS) regime of flight. This research looks to take MFC actuated control surfaces one step further by pulling inspiration from and avian flight. A dual mode control surface, created by applying two sets of two MFCs to patch of carbon fiber, can mimic the tip feathers of a bird. This actuator was modeled both using Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD). Real-world static testing on a feather confirmed preliminary FEA results, and wind tunnel tests simulating assumed cruise conditions confirmed the feather would not exhibit any adverse structural behaviors, such as flutter or aeroelastic divergence. From its modeled performance on a wing using CFD, the MFC feather proved to be a success. It was able to produce a wing that, when compared to a traditional rectangular wing, yielded 73% less induced drag and generated proverse yaw. However, the MFC feathers alone, in the configuration tested, did not produce enough roll authority to feasibly control an aircraft.

abstract: This study identifies the influence that leading-edge shape has on the aerodynamic characteristics of a wing using surface far-field and near-field analysis. It examines if a wake survey is the appropriate means for measuring profile drag and induced drag. The paper unveils the differences between sharp leading-edge and blunt leading-edge wings with the tools of pressure loop, chordwise pressure distribution, span load plots and with wake integral computations. The analysis was performed using Computational Fluid Dynamics (CFD), vortex lattice potential flow code (VORLAX), and a few wind-tunnels runs to acquire data for comparison. This study found that sharp leading-edge wings have less leading-edge suction and higher drag than blunt leading-edge wings. The blunt leading-edge wings have less drag because the normal vector of the surface in the front section of the airfoil develops forces at opposed skin friction. The shape of the leading edge, in conjunction with the effect of viscosity, slightly alter the span load; both the magnitude of the lift and the transverse distribution. Another goal in this study is to verify the veracity of wake survey theory; the two different leading-edge shapes reveals the shortcoming of Mclean’s equation which is only applicable to blunt leading-edge wings. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2019

The bell-shaped lift distribution (BSLD) wing design methodology advanced by Ludwig Prandtl in 1932 was proposed as providing the minimum induced drag. This study used this method as the basis to analyze its characteristics in two wing formation flight. Of specific interest are the potential efficiency savings and the optimal positioning for formation flight. Additional comparison is made between BSLD wings and bird flight in formation. This study utilized Computational Flow Dynamics (CFD) simulations on a geometric modeling of a BSLD wing, the Prandtl-D glider. The results were validated by modified equations published by Prandtl, by CFD modeling published by others, and by Trefftz plane analysis. For verification, the results were compared to formation flight research literature on aircraft and birds, as well as published research on non-formation BSLD flight. The significance of this research is two part. One is that the BSLD method has the potential for significant efficiency in formation flight. The optimal position for a trailing wing was determined to be partially overlapping the leading wing vortex core. For a BSLD wing these vortices are located inboard from the wingtips resulting in wingtip overlap and have a wider impact downstream than the elliptical lift distribution (ELD) wingtip vortices. A second aspect is that avian research has traditionally been studied assuming the ELD model for bird flight, whereas this study proposes that bird flight would be better informed using the BSLD.

Advances in numerical optimization have raised the possibility that efficient and novel aircraft configurations may be ``discovered'' by an algorithm. To begin exploring this possibility, a fast and robust set of tools for aerodynamic shape optimization is developed. Parameterization and mesh-movement are integrated to accommodate large changes in the geometry. This integrated approach uses a coarse B-spline control grid to represent the geometry and move the computational mesh; consequently, the mesh-movement algorithm is two to three orders faster than a node-based linear elasticity approach, without compromising mesh quality. Aerodynamic analysis is performed using a flow solver for the Euler equations. The governing equations are discretized using summation-by-parts finite-difference operators and simultaneous approximation terms, which permit nonsmooth mesh continuity at block interfaces. The discretization results in a set of nonlinear algebraic equations, which are solved using an efficient parallel Newton-Krylov-Schur strategy. A gradient-based optimization algorithm is adopted. The gradient is evaluated using adjoint variables for the flow and mesh equations in a sequential approach. The flow adjoint equations are solved using a novel variant of the Krylov solver GCROT. This variant of GCROT is flexible to take advantage of non-stationary preconditioners and is shown to outperform restarted flexible GMRES. The aerodynamic optimizer is applied to several studies of induced-drag minimization. An elliptical lift distribution is recovered by varying spanwise twist, thereby validating the algorithm. Planform optimization based on the Euler equations produces a nonelliptical lift distribution, in contrast with the predictions of lifting-line theory. A study of spanwise vertical shape optimization confirms that a winglet-up configuration is more efficient than a winglet-down configuration. A split-tip geometry is used to explore nonlinear wake-wing interactions: the optimized split-tip demonstrates a significant reduction in induced drag relative to a single-tip wing. Finally, the optimal spanwise loading for a box-wing configuration is investigated.