Airports are unavoidably noisy places, but if an EU research initiative works out, at least the aircraft buzzing overhead will be a bit quieter. A three-year basic research initiative hopes to find ways of making jet engines a little easier on the ears.
Trinity College has won the honour of leading the project, which involves university and industrial partners, including some of the world's most successful jet engine manufacturers. This level of industrial involvement also ensures that the research will translate as quickly as possible into usable commercial advantage.
Partners include engine-builders, Snecma, Volvo Aero and Rolls Royce Deutschland, and aero frame designer Dassault Aviation. Research institutes include DERA in Britain and ONERA in France, and thirdlevel research partners include Trinity, Chalmers University, Ecole Centrale de Lyon, University of Southampton, University of Poitiers and Instituto Superior Tecnico in Portugal. The 13th partner is the National Institute for Turbomachinery in Romania.
Prof John Fitzpatrick, head of mechanical engineering at Trinity, will lead the project in co-operation with fellow Trinity researcher, Dr Craig Meskell. It is called JEAN for Jet Exhaust Aerodynamics and Noise and has a budget of P2.33 million.
Airlines are being forced to reduce jet aircraft noise, with many countries introducing legislation. "International laws on environmental noise from aircraft are being framed with the intention of significantly reducing the noise at airports," Prof Fitzpatrick said. "We have to comply and in Ireland there will have to be monitoring."
Airports are being asked to police noise pollution and will carry the blame if noise limits are not met. In the Netherlands, Schipol airport was fined heavily last year for exceeding international limits averaged over the year - the "cumulative noise exposure index", Prof Fitzpatrick explained.
In the future, airports will deny "slots", or opportunities to land, if aircraft do not comply with the limits. "As a consequence, airlines are tending to buy quieter planes because the slot availability will be reduced if they have a high noise-exposure rating," he said.
JEAN is just part of a larger research initiative. "Europe has set up a number of thematic networks led by European industry," he said, including one called "X-noise", which looks at noise produced by engines, airframe, flaps and landing gear.
Prof Fitzpatrick is on the scientific committee of X-noise and was approached by European companies to head JEAN, in recognition of his research expertise. "It is nice to be considered to be of sufficient value to do such a project."
The team is developing ways to model how an engine will sound, long before it is actually built. "The object is to be able to use this model to develop new designs so you know how much noise a design will generate." Noise reduction is now an important aspect of engine design and each of the likely noise sources is considered in advance rather than assessing how much noise an engine will make when it has been constructed.
Each of the main components of a modern engine, such as fan, compressor and jet, contributes its own share to the overall noise produced. Old engines were simple propulsion units, with most of the noise coming from jet itself. Newer designs, known as high ratio bypass engines, are much quieter and are being made quieter still. Ironically, this will in time cause the jet to again become the single nosiest component, Prof Fitzpatrick said.
In the JEAN project, the problem of predicting the noise generated by jet exhausts would be addressed in three phases, he explained.
The first will be to develop and validate computer-based models that will predict "the complex exhaust flows" produced by modern aero engines using computational fluid dynamics techniques.
The second phase will couple the aerodynamic predictions to noise source generation and propagation models to estimate the near and far field noise generated by subsonic jets. The results will be evaluated against data obtained from a series of carefully designed experiments.
For the final phase, the validated noise prediction procedures will be applied to exhaust mixing improvements and to co-axial jets and the results compared with existing data for these configurations.
The work will recommend the use of a particular suite of techniques and these will then provide for the development of new concepts in low-noise design of jet engines.
Prof Fitzpatrick believes that this type of modelling is becoming a standard part of engine design. It should make living near an airport a little bit more peaceful.
