Advanced Turbofan-Equipped Aircraft Noise Model

Final Report Summary - FLIGHT-NOISE (Advanced turbofan-equipped aircraft noise model)

Executive summary:

The FLIGHT-NOISE project dealt with aircraft noise from a modern turbofan-powered commercial aircraft. The strategic goal of the project was to develop and validate a comprehensive model to predict the noise at ground receivers. The project consisted in a first phase, in which we gathered the specifications; then we developed the comprehensive model at several levels, including aircraft configurations, engine / propulsion model, flight mechanics, and aircraft noise. In the second phase, the models were validated at all levels, starting from the airplane models, through to the engine performance, the flight mechanics performance, and finally the aircraft noise. The latter point was the real focus of the project.

The noise model was broken down in parts: sources and propagation; the sources were modelled independently from the propagation and from each other. The noise sources were categorised as airframe (non-propulsive) and engine (propulsive). We have provided account for noise from the lifting surfaces (wing, horizontal stabiliser, vertical tail), high-lift systems (flaps and slats) as well as landing gear. On the engine side, we have provided models that account for fan noise, compressor noise, combustor noise, turbine noise, jet noise, APU noise; we have then developed model to simulate interference effects, such as jet-by-jet shielding, wing / fuselage scattering, acoustic liners in a duct. The propagation models consisted of a pure propagation in the free atmosphere, according to ISO models, as well as the effects of wind, relative humidity, temperature shears, ground effect.

The noise models have been validated at three levels: at the level of system component, at the level of integration onto the aircraft, at the trajectory level. For the latter part of the validation, we have used several types of analysis, from synthetic trajectories (comparison with INM V7) to real-life aircraft trajectories. For this purpose, we initiated a data gathering exercise and collected 4 trajectories for the Airbus A319-100 (thanks to the cooperation of DLR / Lufthansa, Germany), and 8 trajectories for the Embraer E195 (thanks to the cooperation of Manchester Airport / FlyBE). The data have been processed and prepared for the validation. Several exercises have been carried out, including (at the end of the project) a code-to-code comparison with DLR-Braunschweig. The validation was successful, and allowed us to make some fair comparisons and assess the overall accuracy of the methods developed under this initiative. The computer code FLIGHT-NOISE was delivered to Thales Avionics (Toulouse, France) at several stages of development. The final version of the code contained three airplane models: Airbus A139-100, Airbus A320-200, Embraer E195, and their respective engines. We conclude that the project was successful and was able to deliver the accuracy requested by the call.

Project context and objectives:

This project aimed to develop simulation methods for aircraft noise, with specific applications to turbofan powered commercial aircraft. All the projects objectives have been achieved. The FLIGHT-NOISE software was delivered to Thales Avionics at the end of the project. The software is capable of predicting real-life aircraft trajectories and is capable of simulating noise from the airframe, the engines and the auxiliary power systems. There are models for the noise propagation, ground effects, wind effects, atmospheric temperature effects. The model has been extensively tested with data from the open literature as well as with data from the flight data recorder. The aircraft modelled under this framework were: Airbus A319-100 with CFM engines, Airbus A320-211 with CFM engines.

Project results:

Results:

1. development of flight mechanics model;
2. development of realistic aircraft model;
3. development of realistic engine models, by using 1-dimensional aerothermodynamic theory;
4. system integration;
5. development of full aircraft noise model;
6. development of validation strategies;
7. collection of validation data, from open literature and from FDR (flight data recorders);
8. verification and validation of the full software system;
9. technical reporting to the sponsors.

Potential impact:

The FLIGHT-NOISE software developed under this research program has a large number of engineering applications. With specific reference to aircraft noise, the software can be used in a variety of scenarios, including, but limited to:

1. flight path optimisation;
2. effects of ground topography on noise propagation;
3. effects of atmospheric conditions, including winds, humidity and temperature shear;
4. noise analysis at airports, specifically noise footprints at landing and takeoff, noise stacks (noise levels from multiple aircraft movements);
5. analysis of a variety of integral noise metrics (SEL, EPNL, LAeqT);
6. parametric analysis to investigate the effects of each noise source.

There is clearly a vast impact, both on society, on the economic impact of aviation. This software can be used by trained professional to help in the formulation of environmental policies, to advice on airport expansions and operations, on the engineering analysis of aircraft noise at a very high technical level. Furthermore, there is potential for further exploitation by continuing the development of the software, and its validation with relevant data. Current areas of work include: acoustic liners, fan noise, fuselage external noise, fuselage internal noise, propeller noise, trajectory optimisation, sensitivity analysis and validation across all the disciplines.