In recent years unconventional aircraft configurations, such as Blended-Wing-Body (BWB) aircraft, are being investigated and researched with the aim to develop more efficient aircraft configurations, in particular for very large transport aircraft that are more efficient and environmentally-friendly. The BWB configuration designates an alternative aircraft configuration where the wing and fuselage are integrated which results essentially in a hybrid flying wing shape. The first example of a BWB design was researched at the Loughead Company in the United States of America in 1917. The Junkers G. 38, the largest land plane in the world at the time, was produced in 1929 for Luft Hansa (present day; Lufthansa). Since 1939 Northrop Aircraft Inc. (USA), currently Northrop Grumman Corporation and the Horten brothers (Germany) investigated and developed BWB aircraft for military purposes. At present, the major aircraft industries and several universities has been researching the BWB concept aircraft for civil and military activities, although the BWB design concept has not been adapted for civil transport yet. The B-2 Spirit, (produced by the Northrop Corporation) has been used in military service since the late 1980s. The BWB design seems to show greater potential for very large passenger transport aircraft. A NASA BWB research team found an 800 passenger BWB concept consumed 27 percent less fuel per passenger per flight operation than an equivalent conventional configuration (Leiebeck 2005). The purpose of this research is to assess the aerodynamic efficiency of a BWB aircraft with respect to a conventional configuration, and to identify design issues that determine the effectiveness of BWB performance as a function of aircraft payload capacity. The approach was undertaken to develop a new conceptual design of a BWB aircraft using Computational Aided Design (CAD) tools and Computational Fluid Dynamics (CFD) software. An existing high-capacity aircraft, the Airbus A380 Contents RMIT University, Australia was modelled, and its aerodynamic characteristics assessed using CFD to enable comparison with the BWB design. The BWB design had to be compatible with airports that took conventional aircraft, meaning a wingspan of not more than 80 meters for what the International Civil Aviation Organisation (ICAO) regulation calls class 7 airports (Amano 2001). From the literature review, five contentions were addressed; i. Is a BWB aircraft design more aerodynamically efficient than a conventional aircraft configuration? ii. How does the BWB compare overall with a conventional design configuration? iii. What is the trade-off between conventional designs and a BWB arrangement? iv. What mission requirements, such as payload and endurance, will a BWB design concept become attractive for? v. What are the practical issues associated with the BWB design that need to be addressed? In an aircraft multidisciplinary design environment, there are two major branches of engineering science; CFD analysis and structural analysis; which is required to commence producing an aircraft. In this research, conceptual BWB designs and CFD simulations were iterated to evaluate the aerodynamic performance of an optimal BWB design, and a theoretical calculation of structural analysis was done based on the CFD results. The following hypothesis was prompted; A BWB configuration has superior in flight performance due to a higher Lift-to-Drag (L/D) ratio, and could improve upon existing conventional aircraft, in the areas of noise emission, fuel consumption and Direct Operation Cost (DOC) on service. However, a BWB configuration needs to employ a new structural system for passenger safety procedures, such as passenger ingress/egress. The research confirmed that the BWB configuration achieves higher aerodynamic performance with an achievement of the current airport compatibility issue. The beneficial results of the BWB design were that the parasite drag was decreased and the spanwise body as a whole can generate lift. In a BWB design environment, several advanced computational techniques were required to compute a CFD simulation with the CAD model using pre-processing and CFD software.

Zugl.: Braunschweig, Techn. Univ., Diss., 2009

Este trabalho tem por objetivo analisar o comportamento aerodinâmico de dispositivos de ponta de asa e Fences acoplados em uma aeronave Blended Wing Body (BWB) através de testes em túnel de vento. A BWB é um projeto de aeronave alternativo que faz parte do conceito de aeronaves sustentáveis. O Laboratório de Aeronaves da Escola de Engenharia de São Carlos, Universidade de São Paulo, vem realizando uma série de pesquisas sobre este assunto. Em trabalhos anteriores com o modelo BWB foram observados a presença tanto de um escoamento transversal na parte externa quanto um forte vórtice no meio do modelo. A fim de melhorar o primeiro protótipo o Droop, bem como um arranjo de três Fences foram adicionados no modelo BWB. Além disso, os dispositivos Winglets e C-wing foram considerados neste estudo. Entre o desenvolvimento de aeronaves, vários dispositivos têm sido estudados e implementados em aeronaves convencionais. Estes tem várias vantagens, tais como a melhoria da eficiência aerodinâmica e a redução do arrasto induzido e efeitos positivos no rendimento do avião. Os dispositivos de ponta da asa criam uma força aerodinâmica em que um do seus componentes atua na direção do voo, esta também pode contribuir para a redução da intensidade dos vórtices nas pontas da asa, reduzindo o arrasto induzido. Pesquisas em aeronaves não convencionais mostraram que BWB poderia ter melhores características aerodinâmicas do que uma aeronave convencional. Aindústriaaeronáuticaestáprocurandoareduçãodoscustosoperacionais,bemcomo a adaptação das aeronaves para a restrição legislativa das emissões de gases e poluição sonora. Nas últimas décadas, esta redução não teve uma melhora significativa em termos de valores absolutos para configurações convencionais, isso fez com que novas e mais eficientes configurações têm sido estudadas. A interferência dos diferentes dispositivos no modelo BWB foram analisados em teste em túnel de vento. Os experimentos foram realizados no Laboratório de Aeronaves da Escola de Engenharia de São Carlos, Universidade de São Paulo. Foi utilizado um túnel de vento fechado com uma seção de teste de 1.7x1.3x3 [m]. O ângulo de ataque foi variado desde -4º a 20º e Re = 390.000. Os resultados mostram que os dispositivos nas pontas da asa melhoraram o desempenho da aeronave, bem como a eficiência aerodinâmica. Com relação aos Fence este comportamento não foi observado. Entre tanto, em ângulos elevados a eficiência foi aumentada. Através da técnica de visualização oil flow observou-se que o escoamento sobre a asa foi redirecionado diminuindo o coeficiente de arrasto em ângulos de ataque elevados. / This work aims to analyze the aerodynamic behavior of wingtip devices and Fences coupled on a Blended Wing Body aircraft (BWB) through wind tunnel tests. The BWB is an alternative of airship design which makes up part of the Green aircraft concept. The Aircraft Laboratory of the School of Engineering of São Carlos-University of São Paulo has been carrying out a lot of research into this subject. In previous works with a BWB model, the presence both of a cross flow on the external part and a stronger vortex in the middle of the model have been observed. In order to improve the first prototype a Droop as well as an arrangement of three Fences were added on the BWB model. Furthermore the Winglets, C-wing devices were considered in this study. Among the aircraft development, several devices have been studied and implemented in conventional aircraft. These ones had several advantages such as improving the aerodynamic efficiency and induced drag reduction and getting positive effects on aircraft performance. The wingtip devices create an aerodynamic force in which one of this components acts in the flight direction, also these can contribute to the reduction of the wingtip vortices strength, reducing the induced drag. Researches in non conventional aircraft has shown that BWB could have better aerodynamic characteristics than a conventional aircraft. The aeronautical industry is looking for the reduction of direct operational cost, as well as the adaptation of aircrafts to the demanding legislative restriction of gas emissions and noise pollution. In the last few decades this reductions has not had a significant improvement in terms of absolute values for conventional configurations, this has meant that new and more efficient configurations have been studied. The interference of the different devices on the BWB model were analyzed in wind tunnel test. The experiments were carried out in the Aircraft Laboratory of the School of Engineering of São Carlos-University of São Paulo. A closed wind tunel with a section work of 1.7x1.3x3 [m] was used. The angle of attack was varied from -4º to 20º and Re = 390.000. The results shows that the wing tip devices improved the aircraft performance as well as the aerodynamic efficiency. Regarding the Fences this behavior was not observed. However, at higher angles the efficiency was increased. Through oil flow visualization it was observed that the flow over the wing was redirected decreasing the drag coeficient at higher attack angles.

Este trabalho tem por objetivo analisar o comportamento aerodinâmico de dispositivos de ponta de asa e Fences acoplados em uma aeronave Blended Wing Body (BWB) através de testes em túnel de vento. A BWB é um projeto de aeronave alternativo que faz parte do conceito de aeronaves sustentáveis. O Laboratório de Aeronaves da Escola de Engenharia de São Carlos, Universidade de São Paulo, vem realizando uma série de pesquisas sobre este assunto. Em trabalhos anteriores com o modelo BWB foram observados a presença tanto de um escoamento transversal na parte externa quanto um forte vórtice no meio do modelo. A fim de melhorar o primeiro protótipo o Droop, bem como um arranjo de três Fences foram adicionados no modelo BWB. Além disso, os dispositivos Winglets e C-wing foram considerados neste estudo. Entre o desenvolvimento de aeronaves, vários dispositivos têm sido estudados e implementados em aeronaves convencionais. Estes tem várias vantagens, tais como a melhoria da eficiência aerodinâmica e a redução do arrasto induzido e efeitos positivos no rendimento do avião. Os dispositivos de ponta da asa criam uma força aerodinâmica em que um do seus componentes atua na direção do voo, esta também pode contribuir para a redução da intensidade dos vórtices nas pontas da asa, reduzindo o arrasto induzido. Pesquisas em aeronaves não convencionais mostraram que BWB poderia ter melhores características aerodinâmicas do que uma aeronave convencional. Aindústriaaeronáuticaestáprocurandoareduçãodoscustosoperacionais,bemcomo a adaptação das aeronaves para a restrição legislativa das emissões de gases e poluição sonora. Nas últimas décadas, esta redução não teve uma melhora significativa em termos de valores absolutos para configurações convencionais, isso fez com que novas e mais eficientes configurações têm sido estudadas. A interferência dos diferentes dispositivos no modelo BWB foram analisados em teste em túnel de vento. Os experimentos foram realizados no Laboratório de Aeronaves da Escola de Engenharia de São Carlos, Universidade de São Paulo. Foi utilizado um túnel de vento fechado com uma seção de teste de 1.7x1.3x3 [m]. O ângulo de ataque foi variado desde -4º a 20º e Re = 390.000. Os resultados mostram que os dispositivos nas pontas da asa melhoraram o desempenho da aeronave, bem como a eficiência aerodinâmica. Com relação aos Fence este comportamento não foi observado. Entre tanto, em ângulos elevados a eficiência foi aumentada. Através da técnica de visualização oil flow observou-se que o escoamento sobre a asa foi redirecionado diminuindo o coeficiente de arrasto em ângulos de ataque elevados. / This work aims to analyze the aerodynamic behavior of wingtip devices and Fences coupled on a Blended Wing Body aircraft (BWB) through wind tunnel tests. The BWB is an alternative of airship design which makes up part of the Green aircraft concept. The Aircraft Laboratory of the School of Engineering of São Carlos-University of São Paulo has been carrying out a lot of research into this subject. In previous works with a BWB model, the presence both of a cross flow on the external part and a stronger vortex in the middle of the model have been observed. In order to improve the first prototype a Droop as well as an arrangement of three Fences were added on the BWB model. Furthermore the Winglets, C-wing devices were considered in this study. Among the aircraft development, several devices have been studied and implemented in conventional aircraft. These ones had several advantages such as improving the aerodynamic efficiency and induced drag reduction and getting positive effects on aircraft performance. The wingtip devices create an aerodynamic force in which one of this components acts in the flight direction, also these can contribute to the reduction of the wingtip vortices strength, reducing the induced drag. Researches in non conventional aircraft has shown that BWB could have better aerodynamic characteristics than a conventional aircraft. The aeronautical industry is looking for the reduction of direct operational cost, as well as the adaptation of aircrafts to the demanding legislative restriction of gas emissions and noise pollution. In the last few decades this reductions has not had a significant improvement in terms of absolute values for conventional configurations, this has meant that new and more efficient configurations have been studied. The interference of the different devices on the BWB model were analyzed in wind tunnel test. The experiments were carried out in the Aircraft Laboratory of the School of Engineering of São Carlos-University of São Paulo. A closed wind tunel with a section work of 1.7x1.3x3 [m] was used. The angle of attack was varied from -4º to 20º and Re = 390.000. The results shows that the wing tip devices improved the aircraft performance as well as the aerodynamic efficiency. Regarding the Fences this behavior was not observed. However, at higher angles the efficiency was increased. Through oil flow visualization it was observed that the flow over the wing was redirected decreasing the drag coeficient at higher attack angles.

The blended wing body (BWB) is a tailless aircraft with the potential to use 27% less fuel than a conventional aircraft with the same passenger capacity and range. The primary purpose of the current study was to determine the handling qualities of the BWB, using piloted-handling trials in a moving-base simulator. The secondary purpose was to determine the effect of simulator motion on handling-quality ratings. De Castro conducted piloted-handling trials in a fixed-base simulator. De Castro's tasks and flight model were modified in the current study. In the current study, three subjects rated the handling qualities as Level 1 or 2, depending on the task. Simulator motion did not have a significant effect on the results.

The blended wing body (BWB) is a tailless aircraft with the potential to use 27% less fuel than a conventional aircraft with the same passenger capacity and range. The primary purpose of the current study was to determine the handling qualities of the BWB, using piloted-handling trials in a moving-base simulator. The secondary purpose was to determine the effect of simulator motion on handling-quality ratings. De Castro conducted piloted-handling trials in a fixed-base simulator. De Castro's tasks and flight model were modified in the current study. In the current study, three subjects rated the handling qualities as Level 1 or 2, depending on the task. Simulator motion did not have a significant effect on the results.

Radical aircraft and propulsion system architecture changes may be required to continue historic performance improvement rates as current civil aircraft and engine technologies mature. Significant fuel-burn savings are predicted to be achieved through the Distributed Propulsion concept, where an array of propulsors is distributed along the span of an aircraft to ingest boundary layer air and increase propulsive efficiency. Studies such as those by NASA predict large performance benefits when integrating Distributed Propulsion with the Blended Wing Body aircraft configuration, as this planform geometry is particularly suited to the ingestion of boundary layer air and the fans can be redesigned to reduce the detrimental distortion effects on performance. Additionally, a conventional aircraft with Distributed Propulsion has not been assessed in public domain literature and may also provide substantial benefits. A conceptual aircraft design code has been developed to enable the modelling of conventional and novel aircraft. A distributed fan tool has been developed to model fan performance, and a mathematical derivation was created and integrated with the fan tool to enable the boundary layer ingestion modelling. A tube & wing Distributed Propulsion aircraft with boundary layer ingestion has been compared with a current technology reference aircraft and an advanced turbofan aircraft of 2035 technology. The advanced tube & wing aircraft achieved a 27.5% fuel-burn reduction relative to the baseline aircraft and the Distributed Propulsion variant showed fuel efficiency gains of 4.1% relative to the advanced turbofan variant due to a reduced specific fuel consumption, produced through a reduction in distributed fan power requirement. The Blended Wing Body with Distributed Propulsion was compared with a turbofan variant reference aircraft and a 5.3% fuel-burn reduction was shown to be achievable through reduced core engine size and weight. The Distributed Propulsion system was shown to be particularly sensitive to inlet duct losses. Further investigation into the parametric sensitivity of the system revealed that duct loss could be mitigated by altering the mass flow and the percentage thrust produced by the distributed fans. Fuel-burn could be further reduced bydecreasing component weight and drag, through decreasing the fan and electrical system size to below that necessary for optimum power or specific fuel consumption.

Increasing environmental concerns and fuel prices motivate the study of alternative, unconventional aircraft configurations. One such example is the blended-wing-body configuration, which has been shown to have several advantages over the conventional tube-and-wing aircraft configuration. In this thesis, a blended-wing-body aircraft is studied and optimized aerodynamically using a high-fidelity Euler-based flow solver, integrated geometry parameterization and mesh movement, adjoint-based gradient evaluation, and a sequential quadratic programming algorithm. Specifically, the aircraft is optimized at transonic conditions to minimize the sum of induced and wave drag. These optimizations are carried out with both fixed and varying airfoil sections. With varying airfoil sections and increased freedom, up to 52% drag reduction relative to the baseline geometry was achieved: at the target lift coefficient of 0.357, a drag coefficient of 0.01313 and an inviscid lift-to-drag ratio of 27.2 were obtained.

Increasing environmental concerns and fuel prices motivate the study of alternative, unconventional aircraft configurations. One such example is the blended-wing-body configuration, which has been shown to have several advantages over the conventional tube-and-wing aircraft configuration. In this thesis, a blended-wing-body aircraft is studied and optimized aerodynamically using a high-fidelity Euler-based flow solver, integrated geometry parameterization and mesh movement, adjoint-based gradient evaluation, and a sequential quadratic programming algorithm. Specifically, the aircraft is optimized at transonic conditions to minimize the sum of induced and wave drag. These optimizations are carried out with both fixed and varying airfoil sections. With varying airfoil sections and increased freedom, up to 52% drag reduction relative to the baseline geometry was achieved: at the target lift coefficient of 0.357, a drag coefficient of 0.01313 and an inviscid lift-to-drag ratio of 27.2 were obtained.

The blended-wing-body (BWB) configuration appears as a promising contender for the next generation of large transport aircraft. The idea of blending the wing with the fuselage and eliminating the tail is not new, it has long been known that tailless aircraft can suffer from stability and control problems that must be addressed early in the design. This thesis is concerned with identifying and then evaluating the flight dynamics, stability, flight controls and handling qualities of a generic BWB large transport aircraft concept. Longitudinal and lateral-directional static and dynamic stability analysis using aerodynamic data representative of different BWB configurations enabled a better understanding of the BWB aircraft characteristics and identification of the mechanisms that influence its behaviour. The static stability studies revealed that there is limited control power both for the longitudinal and lateral-directional motion. The solution for the longitudinal problem is to limit the static margins to small values around the neutral point, and even to use negative static margins. However, for the directional control problem the solution is to investigate alternative ways of generating directional control power. Additional investigation uncovered dynamic instability due to the low and negative longitudinal and directional static stability. Furthermore, adverse roll and yaw responses were found to aileron inputs. The implementation of a pitch rate command/attitude hold flight control system (FCS) improved the longitudinal basic BWB characteristics to satisfactory levels, or Level 1, flying and handling qualities (FHQ). Although the lateral-directional command and stability FCS also improved the BWB flying and handling qualities it was demonstrated that Level 1 was not achieved for all flight conditions due to limited directional control power. The possibility to use the conventional FHQs criteria and requirements for FCS design and FHQs assessment on BWB configurations was also investigated. Hence, a limited set of simulation trials were undertaken using an augmented BWB configuration. The longitudinal Bandwidth/Phase delay/Gibson dropback criteria, as suggested by the military standards, together with the Generic Control Anticipation Parameter (GCAP) proved possible to use to assess flying and handling qualities of BWB aircraft. For the lateral-directional motion the MIL-F-8785C criteria were used. Although it is possible to assess the FHQ of BWB configuartions using these criteria, more research is recommended specifically on the lateral-directional FHQs criteria and requirements of highly augmented large transport aircraft.