Keynote Speakers:There will be seven keynote speeches during the Congress.
- Jing Tian, President of the Chinese Acoustical Societ, China
- Mats Åbom, The Royal Institute of Technology, Sweden
- Goran Pavic, INSA-Lyon, France
- Jose Sanchez Dehesa, Polytechnic University of Valencia, Spain
- Aly El-Shafei, Cairo University, Egypt
- Maria Heckl, Keele University, United Kingdom
- Joachim Scheuren, Muller BBM, Germany
Opportunities for Acoustics in the Ubiquitous Information Society
Jing Tian, President of the Chinese Acoustical Society
Abstract:
Along with the rapid development and wide application of a series of Information Technologies, such as sensor networks, network computing, mobile communications, new mediae and a new generation of broadband Internet, an emerging category of technologies named as "ubiquitous network", has drawn more and more attention of researchers, enterprises and even governments in the new century. Connoisseurs supposed that the human being would come to "u-society" (ubiquitous society) from the e-society. Anyone and anything existing in this "ubiquitous" world could be interconnected and communicated with any other(s) in anytime and anywhere in an "always on" mode. The ubiquity of information and communications will have a significant impact on the current living and manufacturing modes, and will also bring us with great opportunities for correlated technological developments. For acoustics, the challenges and requirements are mainly in the following areas. (1) Sound and vibration sensors and intelligent sensor chips (SoC), especially MEMS microphones and accelerometers integrated with preamplifier circuits, A/D inverters and DSPs etc. (2) Application technology for Internet of Things in environmental noise and vibration monitoring systems. (3) Audio content searching for acoustic event detection and data mining. (4) Virtual soundscope with holographic recording and reconstruction of remote sound field.
Acoustic Multi-ports with application to Duct Acoustics
Mats Åbom, The Royal Institute of Technology, Sweden
Abstract:
In this lecture the development of acoustic multi-port models to describe linear acoustic problems in ducts with flow is presented. From an engineering point of view this field covers many important applications ranging from ventilation ducts in vehicles or buildings to intake/exhaust ducts on IC-engines and power plants. Historically the use of multi-port models for ducts started in the 1920´s, when the four-pole (2-port) filter models used by electrical engineers were applied to analyse transmission of low frequency 1D (plane) waves, e.g., with application to automotive mufflers. An important step was then taken in 1971 when Cremer presented the idea that such "black box" or multi-port models can be applied to describe aerodynamically generated sound in ducts. This implies that any fluid machine or unsteady flow process can be modelled as a "black box" with a passive part, that describes how incident waves are scattered, and an active part, that describes the sound generation. The active part is assumed independent of the acoustic state, which makes the "black box" or acoustic multi-port model consistent with Lighthills acoustic analogy. For linear duct aeroacoustic problems, i.e., cases with linear wave propagation and sound generation uncoupled to the acoustic field, a multi-port represents the most general way of describing acoustic sources. Knowledge of the multi-port data for all active (fans, flow constrictions,...) and passive (straight ducts,...) elements in a duct systems, plus the radiation impedances at duct openings, enables a complete acoustic analysis. This is of course important for engineering acoustics, but to make it useful experimental or numerical methods to determine multi-ports are needed. Since 1970 most of the works done in this field have been focusing on the low frequency 1D (plane) wave range and have been experimental. But the progress in Computational Fluid Mechanics (CFD) during the last 10-15 years has opened the possibility for the determination of both the passive and the active part via numerical methods. In particular the possibility to compute the active part is important. For fluid machines (IC-engines, compressors, fans,....) the periodic part of the spectrum can normally be obtained by so called U-RANS, but the broad-band part requires LES and is still in most cases not feasible to compute. An example of an area where 1-port source data determination via (1D) CFD codes today are common practice is the gas exchange analysis of IC-engines. Recent examples of the use of CFD models to analyse both passive (vortex-sound effects) and active multi-port data will be presented in the lecture. Although multi-port models are linear they can be used to identify amplification of sound due to vortex-sound or thermo-acoustic effects. This interesting possibility is currently being investigated by a number of groups and is of course important for many applications. By making a linear stability analysis of a system using known multi-ports one can predict whistling (poles in the wrong half plane) and also determine the amount of damping needed to avoid it. Regarding the future one can note that very little work exist on multi-ports beyond the low frequency (plane wave) range. Multi-ports including higher order modes are of interest to better model the transition from wave based models ("strong coupling between the source and the system") to the high frequency power based models ("no coupling between source and system") used for, e.g., ventilation ducts.
Visualisation of Sound and Vibration Fields by the Substitute Source Approach
Goran Pavic, INSA-Lyon, France
Abstract:
The substitute source method is a particular modelling technique allowing the use of an analytically available solution of a simple /parent/ object to transform it into the solution of a more complex /child/ object. This technique has been already employed for the computation of sound radiation and/or diffraction but it can be applied to the modelling of vibration fields as well. The method uses the linear superposition principle. The field of the targeted child object driven by the original /primary/ sources is obtained by superposing two fields of the parent object: one produced by the primary sources, the other by secondary /substitute/ sources. The latter are tuned to the primary sources in order to reproduce the boundary conditions along the borders of the child object. The tuning is normally obtained by an inverse procedure which leads to the discretisation of boundary conditions and subsequent matrix computation. Examples of vibration and sound fields are shown to illustrate the technique.
Jose Sanchez Dehesa, Polytechnic University of Valencia, Spain Abstract:
An acoustic metamaterial is a structured system whose properties are extraordinary in comparison with those of materials employed in its fabrication. This paper will review the recent advances on metamaterials based on periodic distributions of sonic scatterers in a fluid or gas background. Emphasis will be given in metamaterials with show anisotropy in the effective mass density. Applications of these metamaterials to engineer acoustic cloaks, gradient index lens and sonic crystals radially periodic will be also reported.
Instability Control and Unbalance Compensation of Flexible Rotors Supported on Journal Bearings Using Magnetic Bearings
Aly El-Shafei, Cairo University, Egypt
Abstract:
This paper presents some new developments in Fluid Film Bearing (FFB) technology. The phenomena of oil whirl and oil whip leading to instability in FFB supported rotors; limit the performance of rotating machinery. This paper presents some new developments that affect the instability threshold, namely the positive effect of angular misalignment on the instability threshold and related design improvements in FFB design. In addition, the concept of an integrated FFB with active magnetic bearing (AMB) is discussed with implications on improving the stability threshold, and actively controlling FFBs.
Thermo-acoustic Instabilities: Modeling and Control
Maria Heckl, Keele University, United Kingdom
Abstract:
If a heat source is put into an acoustic resonator, a thermo-acoustic feedback between the heat release and the acoustic field can occur, which gives rise to intense pressure oscillations. This phenomenon is termed "thermo-acoustic instability". Such instabilities can occur in a variety of combustion-driven devices, such as gas turbines, jet aero engines, rockets and furnaces. They represent a serious problem, because they lead to excessive structural vibrations, fatigue and even catastrophic engine damage.
In recent years, the development of clean combustion systems with reduced pollution of the environment has become a priority. This is achieved by using lean premixed flames and burning at relatively low temperatures. However, such combustion systems are particularly prone to thermo-acoustic instabilities.
This talk aims to give an overview of the key physical mechanisms involved in thermo-acoustic instabilities. It will analyse a very simple thermo-acoustic system, the Rijke tube, and subsequently discuss practical combustion systems. Particular attention will be given to the work going on at Keele University, which focuses on mathematical modelling these instabilities and their control.
The Importance of Research and Development in Acoustics for Practical Noise Control Engineering
Joachim Scheuren, Muller BBM, Germany
Abstract:
Due to the natural pleasance and communicative importance of listening to sounds, the investigation and application of acoustic principles has been constitutive to the cradle of natural science. Starting from supporting acoustic pleasance and communication, this most original discipline of physics has turned more and more into an important technical discipline. This has been strongly pushed forward by the need for well-aimed control of unwanted, annoying or even health affecting sounds and vibrations as inherently generated by the forces and movements of our progressively mechanised world. Today, sound control engineering, i.e. the intentional generation, propagation, incidence, registration, perception and analysis of arbitrary sounds, has become an indispensable element of modern technology.
Thus being established as a most relevant part of modern acoustics, practical noise control engineering has strongly contributed to and benefited from any technical progress in the field of acoustics. And, to meet future challenges, effective noise control engineering will continue to crucially depend on further progress in acoustics.
The lecture demonstrates the mutual importance of motivations, efforts and successes in acoustic research and development. Starting from a historical review of problems and solutions in practical noise control, it will be shown how research on noise effects helped to identify problems, such problems then provoked better insight and methodological approaches and, finally, any related acoustic progress frequently led to innovative solutions in practical noise control.
To further highlight the importance of research and development in acoustics for practical noise control engineering, three recent fields of interest will be presented and discussed in some detail: the conceptive and methodical impact of progress in transfer path analysis and synthesis, the great potential of consequent application of acoustic principles to silent road surface design and the innovative perspectives of active sound control.