[PDF] Numerical Simulation Of Aerodynamic Sound Source In The Wake Of A Complex Object eBook

Author :
Publisher :
Page : 39 pages
File Size : 47,93 MB
Release : 1989
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ISBN :

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Direct Numerical Simulation of Aerodynamic Noise is a part of an overall research program in compressible turbulence including the study of the physics of compressible turbulence, shock-turbulence interactions, reacting flows with heat release, and aerodynamic sound generation in shear flows. The objective of the work in aerodynamic sound generation is to use direct numerical simulations as a tool to study the noise generation processes directly, specifically answer the following questions: 1. Can one relate particular flow regions and events to the far-field noise? 2. What regions are the dominant contributors to the far-field noise? 3. What is the role played by pairing process in noise generation? 4. How important are the small scales to the noise generation? 5. What processes control the far-field directivity pattern? To answer these questions in shear flows, first study the acoustics of simple building block flows. The discussion below presents recent results obtained for one of the building block flows, the scattering of sound by a vortex. A short discussion of numerical accuracy is also given. Finally, results are presented for aerodynamic sound generation from a 2-d temporal mixing-layer. (jhd).

Author : Yaser Khalighi
Publisher :
Page : pages
File Size : 32,53 MB
Release : 2010
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Designing quiet mechanical systems requires an understanding of the physics of sound generation. Among various sources of noise, aerodynamic sound is the most difficult component to mitigate. In practical applications, aerodynamic sound is generated by complex flow phenomena such as turbulent wakes and boundary layers, separation, and interaction of turbulent flow with irregular solid bodies. In addition, sound waves experience multiple reflections from solid bodies before they propagate to an observer. Prediction of an acoustic field in such configurations requires a general aeroacoustic framework to operate in complex configurations. A general computational aeroacoustics method is developed to evaluate noise generated by low Mach number flow in complex configurations. This method is a hybrid approach which uses Lighthill's acoustic analogy in conjunction with source-data from an incompressible calculation. Flow-generated sound sources are computed by using either direct numerical simulation (DNS) or large eddy simulation (LES); scattering of sound waves are computed using a boundary element method (BEM). In this approach, commonly-made assumptions about the geometry of scattering objects or frequency content of sound are not present, thus it can be applied to a wider range of aeroacoustic problems, where sound is generated by interaction of complex flows with solid surfaces. This new computational technique is applied to a variety of aeroacoustic problems ranging from sound generated by laminar and turbulent vortex shedding from cylinders to realistic configurations such as noise emitted from a rear-view side mirror and a hydrofoil. The purpose of each test case, in addition to validation of the method, is to explore various physical and technical aspects of the problem of sound generation by unsteady flows. Through these test cases, it is demonstrated that the predicted sound field by this technique is accurate in the frequency range in which the sound sources are resolved by the computational mesh. It is also shown that in computation of sound, acoustic analogies are less sensitive to numerical errors than direct computations. Finally, a discussion on the efficacy of LES and the effect of sub-grid scale dynamics on predicted sound is presented.

Author : Chris Baker
Publisher : Butterworth-Heinemann
Page : 402 pages
File Size : 22,48 MB
Release : 2019-06-12
Category : Technology & Engineering
ISBN : 0128133112

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Train Aerodynamics: Fundamentals and Applications is the first reference to provide a comprehensive overview of train aerodynamics with full scale data results. With the most up-to-date information on recent advances and the possibilities of improvement in railway facilities, this book will benefit railway engineers, train operators, train manufacturers, infrastructure managers and researchers of train aerodynamics. As the subject of train aerodynamics has evolved slowly over the last few decades with train speeds gradually increasing, and as a result of increasing interest in new train types and high-speed lines, this book provides a timely resource on the topic. Examines the fundamentals and the state-of-the-art of train aerodynamics, beginning with experimental, numerical and analytical tools, and then thoroughly discussing the specific approaches in other sections Features the latest developments and progress in computational aerodynamics and experimental facilities Addresses problems relating to train aerodynamics, from the dimensioning of railway structures and trains, to risk analysis related to safety issues and maintenance Discusses basic flow patterns caused by bridges and embankments

Author : Perry R. Cook
Publisher : CRC Press
Page : 263 pages
File Size : 13,47 MB
Release : 2002-07-01
Category : Computers
ISBN : 1498765467

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Virtual environments such as games and animated and "real" movies require realistic sound effects that can be integrated by computer synthesis. The book emphasizes physical modeling of sound and focuses on real-world interactive sound effects. It is intended for game developers, graphics programmers, developers of virtual reality systems and traini