Design methodologies for aircraft noise estimation with parametric analysis
Creators: name: Marciello, Valerio
Publisher: name: Zenodo
Year: 2020
Subjects: Airframe noise, object-oriented programming, sensitivity analysis.

description: A major challenge in the transport sector is to make economic growth compatible<br> with environmental constraints, while remaining competitive and innovative. The<br> loose integration of engine models into iterative design workflows has prevented aircraft<br> manufacturers from implementing efficient, cost-effective solutions. The search<br> for a new paradigm has led European programmes such as Clean Sky 2 to coordinate<br> and finance research activities aimed at delivering a more sustainable aviation with<br> reduced gas emissions and noise levels. Among these, the ADORNO project has<br> originated from the partnership of the University of Naples with MTU Aero Engines<br> and Lead Tech. Its objectives include the development of a computer method<br> for the prediction of aircraft noise, allowing to consider acoustic emissions from<br> the early stages of design processes. In order to accelerate the attainment of this<br> goal, the candidate has completed an internship activity at the headquarters of MTU. The new software had to comply with several constraints concerning compatibility<br> with the development environments in use at MTU. The new code had to be written<br> in C++, following the paradigms of object-oriented programming. It had to rely on<br> methods capable of predicting the noise generated by moving turbofan aircraft, with<br> reference to microphones placed at arbitrary positions, including both aerodynamic<br> and propulsive sources as well as the effects of sound propagation in the atmosphere. Based on a pre-existing MATLAB code developed at UNINA, the new program<br> has been redesigned by the candidate and named ATTILA++. The employed<br> semi-empirical methods, provided by some ESDU Items, allow to calculate the<br> aerodynamic noise starting from a few geometric data. The engine noise is calculated<br> by external programs and given to the software as additional input. All contributions<br> are adjusted for atmospheric attenuation, ground reflection and lateral attenuation. The first version of ATTILA++ has been completed in compliance with the technical<br> requirements. In order to test its potential, a parametric analysis of the airframe<br> noise has been conducted on a specific regional aircraft, with the main objective of<br> identifying the geometric parameters with the greatest impact on the total noise<br> level. Preliminary results have shown that efforts made to reduce aerodynamic noise<br> are rewarded only in the approach conditions envisaged by the regulatory authority.<br> It has been found that switching from single- to triple-slotted flaps can lead to an<br> increase of + 3.2 dB in airframe noise and + 1.7 dB in the total effective perceived<br> noise level (EPNL). Reducing the flap deflection by 10° has resulted in a reduction<br> of 0.34 % in the total EPNL. Doubling the main wheels has increased the EPNL<br> by 0.53 %, while halving their diameter has led to − 0.26 %. Lastly, the acoustic<br> footprints left by the aircraft during take-off and landing have been reproduced