263 research outputs found

    Optimal airfoil design and wing analysis for solar-powered high altitude platform station

    Get PDF
    The ability of flying continuously over prolonged periods of time has become target of numerous research studies performed in recent years in both the fields of civil aviation and unmanned drones. High altitude platform stations are aircrafts that can operate for an extended period of time at altitudes 17 km above sea level and higher. The aim of this paper is to design and optimize a wing for such platforms and computationally investigate its aerodynamic performance. For that purpose, two-objective genetic algorithm, class shape transformation and panel method were combined and used to define different airfoils with the highest lift-to-drag ratio and maximal lift coefficient. Once the most suitable airfoil was chosen, polyhedral half-wing was modeled and its aerodynamic performances were estimated using the CFD approach. Flow simulations of transitional flow at various angles-of-attack were realized in ANSYS FLUENT and various quantitative and qualitative results are presented, such as aerodynamic coefficient curves and flow visualizations. In the end, daily mission of the aircraft is simulated and its energy requirement is estimated. In order to be able to cruise above Serbia in July, an aircraft weighing 150 kg must accumulate 17 kWh of solar energy per day

    Optimal Propeller design for future HALE UAV

    Get PDF
    Osnovne uloge bespilotnih letelica podrazumevaju: osmatranje, nadzor, prenos robe, daljinsko očitavanje i različite bezbedonosne zadatke. Poboljšana klasa bespilotnih letelica su one koje su posebno projektovane za velike visine leta i duge istrajnosti (uglavnom pri podzvučnim brzinama krstarenja). Do sada je probano nekoliko varijanti koje se razlikuju kako po dimenzijama tako i po primenjenim tehničkim rešenjima. Uobičajeni pristup podrazumeva standarnu konfiguraciju krilotrup-zadnje repne površine i let pomoću elise koja je najefikasnija u tom opsegu brzina. Rad ukratko prikazuje preliminarnu aerodinamičku analizu glavnih uzgonskih površina, ali i detaljniji opis izvedene višekriterijumske optimizacije elise sposobne da obezbedi dovoljni potisak na zadatoj visini i brzini krstarenja. Aerodinamičke performanse razmatranih elisa procenjene su kombinovanim modelom. Izabrani optimizacioni metod, genetski algoritam, pogodan je za probleme koji uključuju veliki broj ulaznih promenljivih.The main roles of unmanned air vehicles (UAVs) include: observation, surveillance, transportation, remote sensing and various security tasks. Improved, augmented type of UAVs are high-altitude long-endurance (HALE) aircraft capable and designed, as their name suggests, for lengthy flights at higher altitudes (which also usually implies subsonic cruising velocities). Different variants, in both size and applied technical solutions, have been tried. Common approach incorporates standard wing-fuselage-aft empennage configuration and propelled flight as the most efficient for the required speed range. The paper gives a brief overview of a preliminary aerodynamic analysis of the main lifting surfaces as well as a detailed description of the performed multi-objective optimization of the propeller capable of producing a sufficient amount of thrust at the cruising altitude and speed. Aerodynamic performances of the investigated propellers are estimated by a simple blade element momentum theory (BEMT). The chosen optimizing method, genetic algorithm (GA), is suitable for dealing with a large number of input variables

    Optimal Propeller design for future HALE UAV

    Get PDF
    Osnovne uloge bespilotnih letelica podrazumevaju: osmatranje, nadzor, prenos robe, daljinsko očitavanje i različite bezbedonosne zadatke. Poboljšana klasa bespilotnih letelica su one koje su posebno projektovane za velike visine leta i duge istrajnosti (uglavnom pri podzvučnim brzinama krstarenja). Do sada je probano nekoliko varijanti koje se razlikuju kako po dimenzijama tako i po primenjenim tehničkim rešenjima. Uobičajeni pristup podrazumeva standarnu konfiguraciju krilotrup-zadnje repne površine i let pomoću elise koja je najefikasnija u tom opsegu brzina. Rad ukratko prikazuje preliminarnu aerodinamičku analizu glavnih uzgonskih površina, ali i detaljniji opis izvedene višekriterijumske optimizacije elise sposobne da obezbedi dovoljni potisak na zadatoj visini i brzini krstarenja. Aerodinamičke performanse razmatranih elisa procenjene su kombinovanim modelom. Izabrani optimizacioni metod, genetski algoritam, pogodan je za probleme koji uključuju veliki broj ulaznih promenljivih.The main roles of unmanned air vehicles (UAVs) include: observation, surveillance, transportation, remote sensing and various security tasks. Improved, augmented type of UAVs are high-altitude long-endurance (HALE) aircraft capable and designed, as their name suggests, for lengthy flights at higher altitudes (which also usually implies subsonic cruising velocities). Different variants, in both size and applied technical solutions, have been tried. Common approach incorporates standard wing-fuselage-aft empennage configuration and propelled flight as the most efficient for the required speed range. The paper gives a brief overview of a preliminary aerodynamic analysis of the main lifting surfaces as well as a detailed description of the performed multi-objective optimization of the propeller capable of producing a sufficient amount of thrust at the cruising altitude and speed. Aerodynamic performances of the investigated propellers are estimated by a simple blade element momentum theory (BEMT). The chosen optimizing method, genetic algorithm (GA), is suitable for dealing with a large number of input variables

    Initial investigation of aerodynamic shape design optimisation for the Aegis UAV

    Get PDF
    This paper presents an aerodynamic design optimisation methodology used in further developing an already existing Unmanned Aerial Vehicle (UAV) platform called Aegis. This paper aims to deliver a medium altitude long endurance UAV for civilian purposes. The methodology used is also applicable to conceptual and preliminary design phases of any aerial vehicle platform. It combines a low fidelity aerodynamic analysis tool, Athena Vortex Lattice Code, with a design optimisation tool (Nimrod/O). The meta-heuristic algorithm, Multi-Objective Tabu Search-2 (MOTS2), is used to perform the optimisation process. This new methodological study optimises the UAV wing planform for level flight. It was used successfully to obtain a set of optimal wing shapes for the Aegis UAV flying at different speeds. Prior to the formulation of the design problem, a parametric study was performed to explore the design space and provide an insight into how the objective functions behave with respect to the design variables. The methodology presented here is not finalized, it is a first step to constructing a general framework that can be used to optimise the design of a twin-boom UAV aerodynamic shape. The interfacing of the already successful packages Nimrod/O, MOTS2, and AVL software produces an initial result that shows the capability of the new methodology to provide correct support decisions making for a design optimisation process that will benefit the entire community of UAV researchers and designers when it is complete

    Multidisciplinary optimisation of an Unmanned Aerial Vehicle with a fuel cell powered energy system

    Get PDF
    ALF/ENGAER 139425-J Bernardo Miguel Teixeira Alves. Examination Committee: Chairperson: COR/ENGAER Luís António Monteiro Pessanha; Supervisors: Prof. André Calado Marta, MAJ/ENGAER Luís Filipe da Silva Félix; Member of the Committee: Prof. Pedro Vieira GamboaPara explorar a utilização de células de combustível a hidrogénio como alternativa viável aos combustíveis nocivos em veículos aéreos não-tripulados, um conceito de UAV de classe I foi desenvolvido no Centro de Investigação da Força Aérea (CIAFA). Este trabalho foca-se nos estudos trade-off realizados durante a sua conceção e na subsequente otimização. Primeiro, uma abordagem de otimização multi-objetivo foi utilizada com o auxílio do algoritmo genético NSGA-II para balancear dois objetivos em conflito: peso reduzido; e elevada autonomia. Conclui-se que é possível voar mais de três horas com um peso máximo à descolagem de 21,6 kg, uma célula de hidrogénio de 800 W e 148 g de hidrogénio. Uma configuração mais pesada com maior potência nominal e mais combustível foi descartada devido a um constragimento na envergadura. Posteriormente, com um conceito que satisfaz os requisitos impostos, uma abordagem multi-disciplinar (MDO) foi utilizada para maximizar a autonomia. O software utilizado foi o OpenAeroStruct, método dos elementos finitos (FEM) e o método da malha de vórtices (VLM) para modelar superfícies sustentadoras. Inicialmente, uma condição de cruzeiro e de carga foram utilizadas com torção geométrica da asa como variável de projeto. Posteriormente, maior complexidade foi introduzida atrav´es da utilização de afilamento, corda e envergadura. Finalmente, uma terceira condição de voo foi introduzida com o intuito de garantir o requisito de perda. Com a utilização de MDO foi possível aumentar a autonomia em 21% satisfazendo todos os requisitos. Este trabalho marca um passo importante no desenvolvimento de um futuro protótipo no Centro de Investigação.To explore the use of hydrogen fuel cells as a feasible alternative to pollutant fuels on Unmanned Aerial Vehicles (UAVs), a class I concept was designed at the Portuguese Air Force Research Centre. This work focuses on the trade-off studies performed during its design and on the optimisation that followed. First, a multi-objective optimisation approach was used with the aid of the Algorithm NSGAII to balance between two conflicting objectives: low weight and high endurance. It was found that it is possible to fly for more than 3 hours with a Maximum Take-off Weight of 21.6 kg, an 800 W fuel cell and 148 g of hydrogen. A heavier configuration with more power and fuel was discarded due to a wingspan constraint. Later, after the concept satisfied the project requirements, Multi-Disciplinary Design Optimisation (MDO) was performed to achieve the maximum endurance possible. The software used was OpenAeroStruct, low fidelity Finite Element Analysis (FEA) and Vortex Lattice Method (VLM) to model lifting surfaces. Initially, a cruise and a load flight point were used with wing geometric twist only as design variable. After, more complexity was added by introducing taper, wing chord and span. Finally, a third flight point was introduced to ensure the stall requirements were satisfied. The use of MDO allowed a 21% increase in endurance with a smaller wing area. Other improvements could not be achieved without violation of the constraints. This work marks an important milestone in the development of a future prototype at the Research Centre.N/

    Анализа, моделирање и оптимизација беспилотне летелице за велике висине на соларни погон

    Get PDF
    High-altitude long-endurance (HALE) or High-altitude platform station (HAPS) are aircraft that can fly in the stratosphere continuously for several months and provide support to military and civilian needs. In addition, HAPS can be used as a satellite at a fraction of the cost and provide instant, persistent, and improved situational awareness. Solar energy is the primary source of energy for these types of unmanned aerial vehicles (UAVs). Solar panels mounted on the wing and empennage capture solar energy during the day for immediate consumption and conserve the remainder for use at night. The main challenges to the successful design of HAPS are finding an appropriate model to calculate airframe weight, materials for structural analysis, designing a wing and propulsion system so that they can be integrated successfully into a unique aircraft configuration and these problems need to be solved. Therefore, this thesis investigates /focuses on the concept of HAPS, optimization of the airfoil, wing design and aerodynamic analysis, experimental analysis of different materials used in the wing structure, structural analysis of the wing and design of novel optimized propeller. The topics covered in the chapters are mentioned below. The first three chapters of this thesis deal with the introduction, review of available literature and previous relevant research, and background of existing high-altitude aircraft and their configurations. Then, in Chapter 4, the initial mission requirements, mission profile, basic characteristics of solar panels, rechargeable batteries, assessment of daily power consumption and battery mass as well as methodologies for the initial estimation of aircraft structural mass and wing loads are discussed. Chapter 5 is dedicated to selecting and defining the appropriate airfoil by using potential flow model and the multi-criteria optimization process. The aerodynamic analysis of wings performed by computational fluid dynamics is shown in Chapter 6. Calculations of aerodynamic coefficients of the wing and the flow field around the wing are presented in this chapter. Chapter 7 is dedicated to the structural design of high-performance slender wings. Tensile tests of a variety of 3D printed polymers and composite materials as well as the effect of ageing and heat treatment on the tensile properties of PLA are presented to investigate their mechanical characteristics. Structural analysis of the wing is presented in Chapter 8. Two different possible solutions of the aircraft's wing structure for high altitudes are presented and their performance is compared through static and modal analyses. Chapter 9 deals entirely with the methodology for designing the optimal propeller intended for highaltitude unmanned aerial vehicles. Coupled aero-structural optimization was performed using a genetic algorithm where input and output parameters and constraints were defined from a set of geometric, aerodynamic, and structural characteristics of the propeller. Finally, main conclusions are presented in chapter 10.Беспилотне летелице за велике висине (ХАЛЕ, ХАПС) су авиони који могу да лете у стратосфери непрекидно неколико месеци и пружају подршку војним и цивилним потребама. Поред тога, ове летелице се могу користити и као економични сателити и обезбеђивати тренутни, стални и побољшани увид у дешавања на Земљи. Сунчева енергија је главни извор енергије овог типа беспилотних летелица. Соларни панели распоређени по крилу и хоризонталним стабилизаторима упијају сунчеву енергију током дана за тренутну потрошњу док се остатак чува за лет током ноћи. Основни изазови успешном пројектовању ХАПС летелица су изналажење одговарајућег модела за процену тежине летелице, материјала за структуралну анализу, пројектовање крила и погонског система који се могу успешно интегрисати у јединствену конфигурацију летелице и ови проблеми морају бити решени. Стога, ова теза истражује/је фокусирана на концепт ХАПС-а, оптимизацију аеропрофила, дизајн и аеродинамичку анализу крила, експерименталну анализу различитих материјала коришћених у структури крила, структуралну анализу крила и дизајн нове оптимизоване елисе. Теме обрађене по поглављима наведене су у наставку. Прве три главе ове тезе баве се уводом, прегледом доступне литературе и претходних релевантних истраживања, као и прегледом постојећих ХАПС летелица и њихових конфигурација. Затим, у глави 4, разматрани су полазни захтеви и мисија, основне карактеристике соларних панела и пуњивих батерија, процена дневне потрошње енергије и потребне масе батерија, као и методологије за почетну процену масе конструкције авиона и оптерећења крила. Глава 5 посвећена је одабиру и дефинисању одговарајућег аеропрофила коришћењем модела потенцијалног струјања и вишекритеријумског оптимизационог поступка. Аеродинамичка анализа крила спроведена методом прорачунске механике флуида приказана је у глави 6. Овде су такође приказани и прорачунати аеродинамички коефицијенти крила као и струјно поље око крила. Глава 7 посвећена је унутрашњој структури високоперформантних витких крила. Описана су спроведена мерења затезних карактеристика различитих 3Д штампаних полимера и композитних материјала, као и ефекти старења и термичке обраде на механичке карактеристике 3Д штампаних епрувета. Структурална анализа крила представљена је у глави 8. Приказана су два различита могућа решења структуре крила авиона за велике висине и упоређене су њихове перформансе кроз статичку и модалну анализу. Глава 9 се у целости бави методологијом пројектовања оптималне елисе намењене беспилотној летелици за велике висине. Овде је спроведена спрегнута аеро-структурална оптимизација помоћу генетског алгоритма где су улазни и излазни параметри и ограничања дефинисани из скупа геометријских, аеродинамичких и структуралних карактеристика елисе. Коначно, основни закључци дати су у глави 10

    An Integrated Method for Airfoil Optimization

    Get PDF
    Design exploration and optimization is a large part of the initial engineering and design process. To evaluate the aerodynamic performance of a design, viscous Navier-Stokes solvers can be used. However this method can prove to be overwhelmingly time consuming when performing an initial design sweep. Therefore, another evaluation method is needed to provide accurate results at a faster pace. To accomplish this goal, a coupled viscous-inviscid method is used. This thesis proposes an integrated method for analyzing, evaluating, and optimizing an airfoil using a coupled viscous-inviscid solver along with a genetic algorithm to find the optimal candidate. The method proposed is different from prior optimization efforts in that it greatly broadens the design space, while allowing the optimization to search for the best candidate that will meet multiple objectives over a characteristic mission profile rather than over a single condition and single optimization parameter. The increased design space is due to the use of multiple parametric airfoil families, namely the NACA 4 series, CST family, and the PARSEC family. Almost all possible airfoil shapes can be created with these three families allowing for all possible configurations to be included. This inclusion of multiple airfoil families addresses a possible criticism of prior optimization attempts since by only focusing on one airfoil family, they were inherently limiting the number of possible airfoil configurations. By using multiple parametric airfoils, it can be assumed that all reasonable airfoil configurations are included in the analysis and optimization and that a global and not local maximum is found. Additionally, the method used is amenable to customization to suit any specific needs as well as including the effects of other physical phenomena or design criteria and/or constraints. This thesis found that an airfoil configuration that met multiple objectives could be found for a given set of nominal operational conditions from a broad design space with the use of minimal computational resources on both an absolute and relative scale to traditional analysis techniques. Aerodynamicists, program managers, aircraft configuration specialist, and anyone else in charge of aircraft configuration, design studies, and program level decisions might find the evaluation and optimization method proposed of interest

    Aerodynamic improvement methods for a medium-altitude long-endurance UAV wing

    Get PDF
    Aerodynamic studies are critical in the development of aircraft and aircraft technology. To this end, a study of three means for improving the aerodynamic performance using range and endurance metrics is presented in this thesis to guide future design iterations of a mediumaltitude long-endurance tactical unmanned aerial vehicle, the Hydra Technologies S45 Bàalam. The results presented are obtained using computational fluid dynamics simulations and are therefore of high fidelity. Surrogate-based modeling using Gaussian processes is used to reduce the number of computationally-intensive simulations required in the optimizations performed. A Bayesian efficient global optimization algorithm using expected improvement is used in the two optimization series. The first set of results establishes the baseline performance of the wing and assesses the impact of an optionally-installed upswept blended winglet on the development of forces on the wing. Results show that the winglet consistently improves the wing aerodynamics. The spanwise distribution of forces shows that the presence of the winglet introduces a component of force in the direction of thrust owing to the curved shape and flow field, thus reducing drag at the wing tip. The second set of results presents an optimization study on global wing parameters. Three planform parameters, the aspect ratio, taper ratio, and sweep angle, as well as the out-of-plane geometric twist angle, are the design variables. Results show that possible improvements are modest at best unless the aspect ratio is increased because there are no significant design levers to increase the lift without causing a greater increase in the drag. Wing twist is identified to be a parameter useful in manipulating the angle of attack at which the maximum lift-to-drag ratio occurs. The third set of results focuses on the aerodynamic enhancements achievable through active morphing of the flexible upper surface of the wing in flight using actuated rods. Three amplitudes of displacement of the deformable surface are used to represent the morphing process simulated at a range of angles of attack and flow speeds over the full flight envelope of the vehicle. Up to 4 % improvement is obtained on the range and endurance metrics. Improvements are not obtained at all flight conditions tested. It is observed that the morphing process gains influence as the Reynolds number becomes higher because of the associated increase in turbulent flow on the wing which can be delayed to obtain improved aerodynamic coefficients

    CONTENTS

    Get PDF
    corecore