Although modern aircraft are much quieter than their predecessors, the growth in the size of the airliner fleet and number of movements over the last few decades has ensured that noise continues to be a social and political issue. As a consequence, the noise constraints on modern aircraft continue to tighten and noise assessment and reduction remain an important part of the process of designing new aeroengines.
This set of proceedings follows the usual format of the Von Karman Institute (VKI) Lecture Series, with several international experts in the field having been invited to present an introduction or overview of a particular topic. When taken together, the series of lectures are intended to form an introduction for engineers and scientists entering the field.
The initial two lectures in this volume are presented by representatives of industry and are used to set the scene for the more technical topics that follow. The first, presented by Nicolas Tantot of Snecma, looks at the factors that control aeroengine efficiency and how this is driving engine architectures towards ultra-high bypass ratios and open rotors. This is followed by a discussion of engine-airframe aeroacoustic integration and installation effects by Thomas Nodé-Langlois of Airbus. He starts by looking at the noise certification process before moving on to consider how other design decisions, from inlet geometry to the way the engine is mounted on the aircraft, may have an impact on noise.
Christophe Schram of VKI then kicks off the more technical presentations with an introduction to acoustics and flow noise. He begins from first principles in deriving the wave equation, moves rapidly on to consider the various acoustic analogies on which most analytical methods are based, and finally considers numerical acoustics in the form of finite and boundary element methods. Although he covers a lot of ground, the information is well presented and remains pleasingly readable.
The following three lectures are all given by Michel Roger from Ecole Centrale de Lyon and consider analytical methods for turbomachinery noise prediction. Firstly, we are introduced to the noise of open rotors, covering isolated rotors, rotor-wake interactions and then counter-rotating propellers, the emphasis being on the treatment of rotating sources rather than prediction of source levels. In Roger's second lecture, he introduces the effect of a hard-walled annular duct on the generation and propagation of sound. In his third lecture, he takes us through the modelling of various blade and vane aerodynamic sound sources.
Combustion noise and thermoacoustics are covered in a lecture by Maria Heckl from Keele University, with the emphasis clearly on thermoacoustic instabilities. She begins by using the Rijke tube to introduce fluctuating heat release as a source of sound, before moving on to instabilities in combustion systems.
The next lecture, on aeroengine nacelle liner design and optimisation, is presented by Gwenael Gabard from the ISVR at the University of Southampton. He begins by considering sound absorption by perforated liners, then how this is related attenuation of sound propagating in a duct, and finally how liners are optimised for a given sound source and duct geometry.
Jet noise, both subsonic and supersonic, is addressed by Messrs Bailly, Bogey, Marsden and Castellain from the LMFA in Lyon. They begin with a discussion of the sources and scaling laws, before moving on to discuss control of subsonic jet noise and supersonic jet noise mechanisms in more depth.
Mario Felli of the Italian National Maritime Technology Research Institute then presents a lecture on experimental methods applied to jet noise, starting with purely acoustic methods for source location before moving on to more interesting techniques which attempt to relate aerodynamic events with noise production.
In the final lecture of the series, Roberto Camussi of Università Roma Tre discusses advanced analysis techniques for identification of noise sources in turbulent flows. He introduces wavelet transforms, Linear Stochastic Estimation and Proper Orthagonal Decomposition, and then considers the application of these to some typical aeroacoustic problems, including jet noise, turbulent boundary layers and fan-tip leakage.
These proceedings are all well written, clearly presented and easy to follow. The presenters are all active researchers and engineers, and, consequently, the information is topical and current. The long lists of references and bibliographies provide an excellent starting point for further study. The preface to the volume claims, rather boldly, that all sound production mechanisms are addressed. This is not the case, as some aeroengine noise sources, such as engine handling bleed valves and broad-band combustion noise, are missing. But these are minor omissions, and it is fair to say that all the major sources are covered. This lecture series would indeed constitute an excellent introduction for engineers, scientists and PhD students entering the field.
