JINA: Jet Installation Noise Abatement

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.

Impact on People - Exposure to high levels of noise over long periods of time can cause serious physiological to psychological problems, such as hearing impairment, communication interference, sleeplessness, annoyance, task interference, learning difficulties, etc. This is particularly the case for the residential areas near large airports. The significant increase in the number of short- and mid-range flights in the near future will mean that more people will be exposed to high levels of noise. A significant part of the aircraft overall noise, particularly at take-off, is due to the jet and jet-wing interaction noise. JINA will help us better understand the noise generation mechanism and for the first time, proposes a well-structured methodology to develop a high-fidelity joint computational and experimental optimization platform to reduce the jet installation noise.

Impact on industry - The proposed work in JINA is of high relevance to the aviation industry, where the implementation of multi-fidelity modelling based on a range of state-of-the-art acoustic models of jet installation noise based on multi-fidelity LES solutions, and corresponding experimental campaign, for future low-noise exhaust systems will allow aircraft jet engines to be designed more rapidly with reduced physical verification and validation. This is clearly reflected in the letters of support by Airbus, Embraer, and DLR. The high-quality experimental and computational data produced and released as part of the JINA project will also enable development of more robust empirical and semi-empirical jet-installation noise prediction, which again will be of great importance of the development of more accurate in-house prediction tools for the aviation industries.