The accurate and efficient estimation of aircraft loads is an important problem in the aerospace industry. The extreme values of these loads are typically the key parameters used for sizing the aircraft's structure and, therefore, have a significant influence on the performance of an aircraft. Inaccurate estimations of these loads will lead to poor design choices, most typically a conservative structure design that is overweight, increasing energy consumption, toxic emissions, and noise pollution. This research will develop tools for the efficient identification of uncertainties and nonlinearities in aircraft structural components and investigate how they affect aircraft loads. Only nonlinearities and uncertainties in the joints will be considered in this project, but the developed framework can be used for other sources of nonlinearities and uncertainties, such as aerodynamics and flight control systems. Developing such a framework is crucial in order to overcome the predominant practice whereby aircraft designs are restricted to a deterministic and linear regime, despite rapidly increasing demands to consider unavoidable uncertainties and nonlinearities from technological, economic and safety considerations. In this project, a detailed and sophisticated numerical model of an aircraft structure will be used to explicitly identify the possible range of variations in the dynamic response due to geometric and material uncertainties and nonlinearities of a wing-store joint. These data will then be used to identify the parameters of reduced-order models (ROMs). ROMs are extremely useful for computational efficiency, and are used to efficiently predict extreme unsteady loads. The validated reduced-order structural model will be incorporated into the aeroelastic model and will allow the designer to include the effects of nonlinearities and uncertainties in the process of load calculations. The goal is to move away from the conventional safety-factor-based approach and explore the wide horizon of stochastic nonlinear aeroelastic analysis. This project will be carried out in partnership with Airbus, which will provide the data necessary to undertake the research. Since it has been observed that multiple sources of nonlinearities and uncertainties affect aircraft performance, the study aims to investigate the following questions: 1- How can detailed numerical models be used in the identification of sources of nonlinearities and uncertainties? 2- How can the structural model updating tools (the tools that will be used to validate the numerical model based on experimental data or detailed finite element predictions) be used to obtain ROMs that are capable of including the nonlinear and uncertain effects estimated by detailed numerical models? 3- How can these validated ROMs be used to efficiently investigate the effects of uncertainties and nonlinearities in aircraft load predictions (important parameters that have significant impact on aircraft performance)? The aforementioned questions will be answered by considering an important source of nonlinearities and uncertainties in the aircraft structure, i.e. structural joints.

Next-generation aircraft are likely to require significant changes in technology to meet ambitious targets on fuel burn, CO2, NOX and noise emissions. Integrated computer-aided engineering is a key enabler to mitigate the risk coming with disruptive change and new design concepts. Moreover, the long-term vision of digital aircraft design and certification, to reduce reliance on wind tunnel and in-flight testing, requires leaps in highest-fidelity flow simulation. We revisit a grand challenge of aircraft aerodynamics using both state-of-the-art industrial and next-generation simulation tools enabled for the identification of coherent flow structures targeting the mechanisms leading to transonic wing shock buffet and constituting the instability, which despite intensive research efforts remains controversial. Shock buffet manifests itself as a flow instability in high-speed flight with detrimental effects on the aircraft performance, economic efficiency, and ultimately passenger safety. A vast amount of literature on flow instability exists, yet analysis of practical flows relevant to the aerospace industry is limited and often confined to simplified cases. Two key technology demonstrations provide the background to the work. The first is a recent global stability analysis of transonic shock buffet flow with three inhomogeneous spatial directions on an industry-relevant test case using an industry-grade computational fluid dynamics (CFD) solver suite and a Reynolds-averaged Navier-Stokes (RANS) aerodynamic model. However, high confidence in industry-standard CFD solutions is given only in a small region in the operating flight envelope near the cruise point due to the unavailability of general models to predict turbulent separated flow. Hence, the second recent key achievement is high Reynolds number direct numerical simulation (DNS) of supercritical transonic aerofoil flow, which also provides access to global modes. The premise of the work programme is that significant new elements, relying on high-performance computing and advanced numerical flow analysis, are in place to develop next-generation buffet prediction schemes suitable for next-generation transonic wings. We investigate global and resolvent mode analysis across the range of aerodynamic models (from RANS to DNS) applied to low-drag configuration (swept, laminar flow, supercritical) aerofoils and wings, culminating in a modern long-range, wide-body aircraft wing geometry. The practical aim is to develop robust, cost-effective methods to determine the buffet boundary of the wings of the future. Along the way, we will learn more about the physics of shock-induced unsteadiness and the mechanisms leading to shock buffet in the flow around transonic wings.

Air transportation is becoming more accessible to a greater number of people who can afford to travel by air. The air transportation sector forecasts that passenger and freight traffic will increase at an average rate of 4-5% per annum over the next two decades, leading to a doubling of the aircraft fleet by 2034 with respect to 2015. Formidable progress has been made since the introduction of jet-propelled aircraft about 65 years ago, but much of this improvement is offset by the huge increase in air traffic today. The Advisory Council for Aviation Research and Innovation in Europe (ACARE) "FlightPath 2050" calls for reductions of 75% in fuel burn, 65% in perceived noise, and 90% in oxides of nitrogen emissions by 2050 compared to the year 2000. NASA has proposed similar goals in the US for the "N+2" (service-entry 2025) and "N+3" (service-entry 2030-2035) generations of aircraft. These environmental constraints have generated a large effort to reduce the aerodynamic drag and to generate more efficient engines. A small reduction in fuel burn multiplied by the total number of transport aircraft leads to a significant reduction of emissions into the atmosphere. The FALCon project will develop new methods and tools to design a new generation of transport aircraft that take advantage of wing flexibility to improve the global aircraft efficiency. The project is specifically developed around a long-standing industrial challenge: assessing the impact of aerodynamic changes on the structural loads used for structural sizing of aircraft components is an expensive process (from several weeks when low-order methods are employed, to several months when employing higher-fidelity methods). Generally, the computing cost of an aeroelastic analysis is largely dominated by the aerodynamic analysis. The novelty of the FALCon project lies in the development of a computationally-efficient aerodynamic solver that reduces the computational time by, at least, 80% compared to current state-of-the-art methods. The FALCon project will contribute to: - Improved realism of predictions earlier in the aircraft design process, reducing the risk of not meeting customers' expectations and shortening the time to bring new aircraft on the market. - Reduce current conservatism in aircraft design by performing dynamic (time-domain) aeroelastic analysis, which are today neglected because of the computational costs. - Implement a paradigm change in aircraft design through the development of enhanced design tools for conceptual and preliminary phases, including aero-servo-elastic design constraints from the start of the design process. A new design paradigm is proposed, shifting the structural deformability from a performance limitation to a design opportunity. - A close collaboration with industry guarantees that the outcomes of the project will feed back to the UK and European aviation sector, strengthening its competitiveness. A seamless integration within the existing industrial design process is expected, adding no complications to current procedures.

Aircraft noise is known to be responsible for many physiological and psychological effects. According to the recent studies, aircraft noise not only creates a nuisance by affecting amenity, quality of life, productivity, and learning, but it also increases the risk of hospital admissions and mortality due to strokes, coronary heart disease, and cardiovascular disease. The World Health Organization estimated in 2011 that up to 1.6 million healthy life years are lost annually in the western European countries because of exposure to high levels of noise. The noise is also acknowledged by governments and airport operators as a limit to both airline fleet growth and their operations, with direct consequences to the UK economy. Based on the EUROCONTROL forecasts, the air traffic in Europe is expected to continue its long-term growth trend and the number of flights will increase by up to 2.2 times from 2010 to 2030, with the potential increase in related environmental nuisances, particularly noise. As a result, ever more stringent environmental regulations are now in place to reduce the impact of aircraft noise. It is, therefore, of great importance for major aviation industries, such as Airbus and Embraer, to better understand the aerodynamic noise generation mechanisms and develop more robust and effective methods to reduce the noise at source. While the introduction of high bypass ratio turbofans led to significant improvement of the aerodynamic performance of jet engines, it also brought about an aeroacoustical challenge, known as the "jet installation effect", due to the interaction of the jet hydrodynamic field with the high lift device components. The interaction of the jet linear or non-linear hydrodynamic field with the high-lift device components results in a significant increase of noise at low frequencies and also the potential emergence of some aharmonic tones. While a number of very recent studies have provided some insights into the physics of the low-frequency noise amplification in the case of simple circular jets, our current understanding of the interplay between the jet hydrodynamic field, the flow instabilities and the trapped acoustic modes, particularly for non-conventional jets, which generates noise, remains very limited. Our approach in JINA is to reduce the low-frequency noise amplification by the manipulation of the jet hydrodynamic field via nozzle shape optimization. The JINA campaign will bring together expertise in experimental and computational aeroacoustics and design optimization, alongside a strong international advisory and industrial board, aiming at the development of fundamental understanding of jet installation noise, leading to design and manufacture of next-generation quiet jet engines.

Hydraulic fluid power is widely used in land, sea and air transportation, construction machinery, industrial machinery, agricultural machinery, oil and gas, mining and defence. However hydraulic systems are inherently very noisy and new techniques for fluid-borne noise (FBN) attenuation are needed to achieve acceptable and safe noise levels as documented in The Health and Safety Executive 'The Control of Noise at Work Regulations 2005'. It is obvious that low-noise hydraulic machines can significantly improve people's working environment and quality of life. Hydraulic systems are often inefficient with an average efficiency of 21%. An average 5% improvement in efficiency can save 0.51 quadrillion Btu of energy and US$10.1 billion while reducing carbon dioxide emissions by more than 33.95 million metric tons, according to the recent study of 'Estimating the Impact (Energy, Emission and Economics) of the US Fluid Power Industry, 2011'. Some new techniques such as 'digital' fluid power promise much lower energy losses but are hampered by higher noise levels according to the findings from the recently completed research project (EPSRC grant EP/H024190/1). Effective noise control techniques should enable use of these more efficient hydraulic systems, resulting in considerable reduction in fuel consumption and carbon dioxide emissions. The noise in hydraulic circuits presents itself as FBN, structure borne noise and air borne noise. FBN is caused by the unsteady flow produced by pumps and motors or 'digital' hydraulics, and propagates through the system causing vibration or structure borne noise, which in turn causes air borne noise. Traditional noise control measures can lead to additional power losses. Unwanted noise also consumes energy and generates heat which may lead to machines instability and failures. In response to the engineering challenges in noise control and energy efficiency, this proposal is a timely investigation into a novel integrated noise attenuation system for hydraulic machines. The proposed research would be a world first, and will apply a newly integrated noise control approach engaging both active and passive control methods to obtain an effective, robust and high-bandwidth noise attenuation for fluid power systems. Uniquely, this new approach allows the dominant harmonic pressure pulsations to be attenuated by the active attenuator and high frequency noise to be cancelled by passive tuned flexible hoses without impairing the system dynamic response. This novel methodology can significantly improve the noise attenuation performance. Simulations of a generic integrated FBN control system studied by the PI show that 55dB attenuation was achieved, while 40dB was achieved by only using the active control method and 20dB was achieved by using the passive control approach, respectively. The research outcomes will deliver effective solutions to replace traditional noise control equipment and provide input into the development of quieter fluid power machines in the UK and worldwide. The experimental results will provide confidence in applying the integrated FBN control system and design methodology for both conventional and 'digital' hydraulic machines. This research will maintain my research group's unique world leading position and accelerate research impact to ensure the UK remains internationally competitive. This work will ensure the UK's significant role in the global market for hydraulic components which is projected to reach US$67.8 billion by 2020 and further enhance the UK's leading position in the European hydraulic market. It will also help ensure that the UK is well equipped to deal with noise challenges in hydraulic engineering and has the research capability and quantitative skills for worldwide environmental and energy challenges it may face in the future.