AERODYNAMICS & AEROACOUSTICS OF COMPLEX GEOMETRY HOT JETS

With the projected demand for air transport set to double the world aircraft fleet by 2020 it is becoming urgent to take steps to reduce the environmental impact of take off noise from aircraft. In the worst case noise can be more than just annoying, potentially being a contributory factor towards illnesses such as hypertension. Hence, the Advisory Council for Aeronautics Research in Europe (ACARE) has set the target of reducing perceived noise levels by 50% by the 2020. Continual reductions in permitted take-off noise levels are placing the commercial viability of more established plane models in jeopardy giving strong economic implications for the current work. The work proposed merges and extends two recently competed and highly successful EPSRC jet noise projects - GR/S43191/01 and GR/T06629/01. In GR/T06629/01 - rated tending to Outstanding - Large Eddy Simulation (LES) type predictive techniques for complex geometry jets were explored. During the previous GR/S43191/01 (rated Outstanding) project a RANS (Reynolds Averaged Navier-Stokes) based model for turbulent isothermal jet noise, based on an acoustic analogy was developed that is informed by LES. The model was proven to be more accurate for sound predictions, both for the sideline and aft angles to the jet, than previous acoustic models. It provided insights into the mechanisms of noise generation. Here we wish to extend the model to hot jets and complex nozzles, such as chevrons and co-axial jets, which will be of immediate interest to engine manufacturers. We also wish to contrast the model's performance with NASA Glenn, Southampton University and other models. There is very little understanding of the impact of the various space-time correlations of velocity and temperature or indeed the magnitude of these correlations themselves for hot jets. Hence, this flow physics element will be explored thus linking with the current research thrusts at NASA Glenn and the University of Poitiers.

The potential benefits to society and hence impact beyond academia of this project is high, the project's nature being industrially and environmentally inspired. With the projected demand for air transport set to double the world aircraft fleet by 2020 it is becoming urgent to take steps to reduce the environmental impact with respect to noise emissions. At the same time continual reductions in permitted take-off noise levels are placing the commercial viability of more established plane models in jeopardy giving strong economic implications for the current work. With regards to the UK economy we expect that the current work will have strong technological impact, especially for Rolls-Royce plc. All the applicants are part of the Rolls-Royce University UGTP (University Gas Turbine Partnership). Hence, we expect strong engagement with Rolls-Royce plc from the start. This will naturally take place through continuing the regular interactions we have with their engineers. The methods will help ensure that imperative regulatory noise emissions targets can be met, and the potential to manufacture quieter and more efficient engines offers tremendous competitive business advantage; thus creating greater wealth for the UK and securing employment. The project will itself produce three highly trained aerodynamicists/aeroacousticians - who will have benefitted from regular supervision by investigators with diverse and in depth expertise as well as their own interactions with Rolls-Royce & the overseas collaborators (NASA Glenn and the University of Poitiers). This training should thus be of direct value to the UK science/technology base, and there is a well-established recruitment route for such researchers into Rolls-Royce and other key UK aerospace companies. Improved computational and mathematical modelling technology will additionally offer the potential for substantially reduced design costs and time to market for aero engines. We will disseminate the computational and experimental procedures developed to Rolls-Royce plc as well as the wider R&D community. In summary, the planned work has great environmental importance for directly improving the quality of people's lives. It also has commercial importance, potentially safeguarding UK jobs in a high technology area. This is because greater physical understanding, better mathematical models, and valuable new predictive technology for acoustics design will be created. This could potentially ultimately result in more environmentally friendly and hence commercially competitive aircraft that can be brought to the market more quickly and at lower cost. The LES, acoustic and measurement technology devised during the project along with the physical insights should thus all have substantial impact. The work also has wide potential application beyond acoustics and turbomachinery since generic predictive and measurement technologies will be developed as well as insights into turbulence physics for non-isothermal flows.