Noise Sources in Turbulent Shear Flows
April 18, 2011 — April 22, 2011
- Roberto Camussi (Università di Roma Tre, Roma, Italy)
A knowledge of the physical mechanisms underlying the generation of noise in turbulent shear flows remains a challenging task despite over 50 years of intensive research in the field. The interest in this topic is considerable since turbulent shear flows are encountered in many engineering applications including, for example, turbulent boundary layers with and without pressure gradients, compressible and incompressible jet flows and wakes behind streamlined or bluff bodies. An accurate knowledge of the noise generation mechanisms is a fundamental step for both theoretical modelling and practical applications leading, for instance, to the development of flow/noise manipulation techniques and noise suppression devices. Recent developments in terms of our capacity to both numerically and experimentally analyse the physics of turbulent shear flows have opened up new possibilities to improve our knowledge about the noise generation and propagation mechanisms. The aim of the course is to present a state-of-the-art review of on-going activities in noise prediction, simulation and measurement and to indicate current research directions in a way that is accessible to attendees coming from both academic and industrial areas. To this purpose, introductory lectures on fundamentals of aeroacoustics will be followed by up-to-date reviews of topics of specific interest for engineering applications. The first part of the course is denoted as “Fundamentals” and includes two lectures. The first one, opening the course, is devoted to general concepts of aeroacoustics. The second one, is again dealing with general issues but more directly correlated with the need for simulating numerically aeroacoustic problems. This lecture will deal with computational aspects but elucidates more general issues spanning from noise generation mechanisms to noise propagation in turbulent flows.
In the second part of the course, denoted as “Specific Topics”, particular emphasis will be put on topics of relevant interest for engineering applications and aircraft design. These topics will include:
– Self-sustained oscillations generated, for examples, in cavity flows as a result of feed-back resonance mechanisms.
– Fundamentals and modelling of jet noise, including some references to the problem of jet noise control.
– Experimental aspects dealing with aeroacoustics measurements with emphasis not only to measurement techniques and post-processing procedures but also to methods commonly adopted for noise sources identification.
– Noise from moving surfaces, such as airfoils (self-noise and trailing edge noise) or turbine blades.
– Duct acoustics and acoustic wave propagation in closed domains.
– Boundary layer noise with particular emphasis on theoretical aspects related to the statistical modeling of wall pressure fluctuations in attached and separated wall flows.
All these arguments will be treated extensively with the inclusion of many examples of practical applications. The main objective of this course is therefore to allow an information transfer between well-known scientists, leaders in the field of aeroacoustics, and industries and laboratories. Indeed, the lecturers, coming from European countries and from US, are all leading experts in the field of aeroacoustics covering both basic theoretical aspects and the state-of-the-art in industrial high-end applications.
KEYWORDS: Noise, Vibration, Turbulent flow.