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Aeroacoustics of Turbulent High-Speed Jets

Author : National Aeronautics and Space Administration (NASA)

Publisher : Createspace Independent Publishing Platform

Page : 38 pages

File Size : 23,56 MB

Release : 2018-06-30

Category :

ISBN : 9781722052225

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Book Description

Aeroacoustic noise generation in a supersonic round jet is studied to understand in particular the effect of turbulence structure on the noise without numerically compromising the turbulence itself. This means that direct numerical simulations (DNS's) are needed. In order to use DNS at high enough Reynolds numbers to get sufficient turbulence structure we have decided to solve the temporal jet problem, using periodicity in the direction of the jet axis. Physically this means that turbulent structures in the jet are repeated in successive downstream cells instead of being gradually modified downstream into a jet plume. Therefore in order to answer some questions about the turbulence we will partially compromise the overall structure of the jet. The first section of chapter 1 describes some work on the linear stability of a supersonic round jet and the implications of this for the jet noise problem. In the second section we present preliminary work done using a TVD numerical scheme on a CM5. This work is only two-dimensional (plane) but shows very interesting results, including weak shock waves. However this is a nonviscous computation and the method resolves the shocks by adding extra numerical dissipation where the gradients are large. One wonders whether the extra dissipation would influence small turbulent structures like small intense vortices. The second chapter is an extensive discussion of preliminary numerical work using the spectral method to solve the compressible Navier-Stokes equations to study turbulent jet flows. The method uses Fourier expansions in the azimuthal and streamwise direction and a 1-D B-spline basis representation in the radial direction. The B-spline basis is locally supported and this ensures block diagonal matrix equations which are solved in O(N) steps. A very accurate highly resolved DNS of a turbulent jet flow is expected. Rao, Ram Mohan and Lundgren, Thomas S. Ames Research Center NCC2-5017; DAAL03-89-C-0038...





Computational Aeroacoustics

Author : Jay C. Hardin

Publisher : Springer Science & Business Media

Page : 525 pages

File Size : 46,65 MB

Release : 2012-12-06

Category : Science

ISBN : 1461383420

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Book Description

Computational aeroacoustics is rapidly emerging as an essential element in the study of aerodynamic sound. As with all emerging technologies, it is paramount that we assess the various opportuni ties and establish achievable goals for this new technology. Essential to this process is the identification and prioritization of fundamental aeroacoustics problems which are amenable to direct numerical siIn ulation. Questions, ranging from the role numerical methods play in the classical theoretical approaches to aeroacoustics, to the correct specification of well-posed numerical problems, need to be answered. These issues provided the impetus for the Workshop on Computa tional Aeroacoustics sponsored by ICASE and the Acoustics Division of NASA LaRC on April 6-9, 1992. The participants of the Work shop were leading aeroacousticians, computational fluid dynamicists and applied mathematicians. The Workshop started with the open ing remarks by M. Y. Hussaini and the welcome address by Kristin Hessenius who introduced the keynote speaker, Sir James Lighthill. The keynote address set the stage for the Workshop. It was both an authoritative and up-to-date discussion of the state-of-the-art in aeroacoustics. The presentations at the Workshop were divided into five sessions - i) Classical Theoretical Approaches (William Zorumski, Chairman), ii) Mathematical Aspects of Acoustics (Rodolfo Rosales, Chairman), iii) Validation Methodology (Allan Pierce, Chairman), iv) Direct Numerical Simulation (Michael Myers, Chairman), and v) Unsteady Compressible Flow Computa tional Methods (Douglas Dwoyer, Chairman).





Aeroacoustic Measurements

Author : Thomas J. Mueller

Publisher : Springer Science & Business Media

Page : 327 pages

File Size : 13,57 MB

Release : 2013-11-27

Category : Technology & Engineering

ISBN : 3662050587

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Book Description

The book describes recent developments in aeroacoustic measurements in wind tunnels and the interpretation of the resulting data. The reader will find the latest measurement techniques described along with examples of the results.





Combustion Noise

Author : Anna Schwarz

Publisher : Springer Science & Business Media

Page : 304 pages

File Size : 23,47 MB

Release : 2009-06-17

Category : Technology & Engineering

ISBN : 3642020380

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Book Description

November, 2008 Anna Schwarz, Johannes Janicka In the last thirty years noise emission has developed into a topic of increasing importance to society and economy. In ?elds such as air, road and rail traf?c, the control of noise emissions and development of associated noise-reduction techno- gies is a central requirement for social acceptance and economical competitiveness. The noise emission of combustion systems is a major part of the task of noise - duction. The following aspects motivate research: • Modern combustion chambers in technical combustion systems with low pol- tion exhausts are 5 - 8 dB louder compared to their predecessors. In the ope- tional state the noise pressure levels achieved can even be 10-15 dB louder. • High capacity torches in the chemical industry are usually placed at ground level because of the reasons of noise emissions instead of being placed at a height suitable for safety and security. • For airplanes the combustion emissions become a more and more important topic. The combustion instability and noise issues are one major obstacle for the introduction of green technologies as lean fuel combustion and premixed burners in aero-engines. The direct and indirect contribution of combustion noise to the overall core noise is still under discussion. However, it is clear that the core noise besides the fan tone will become an important noise source in future aero-engine designs. To further reduce the jet noise, geared ultra high bypass ratio fans are driven by only a few highly loaded turbine stages.





Computational Aeroacoustics

Author : Christopher K. W. Tam

Publisher : Cambridge University Press

Page : 497 pages

File Size : 16,91 MB

Release : 2012-09-28

Category : Technology & Engineering

ISBN : 1139576569

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Book Description

Computational aeroacoustics (CAA) is a relatively new research area. CAA algorithms have developed rapidly and the methods have been applied in many areas of aeroacoustics. The objective of CAA is not simply to develop computational methods but also to use these methods to solve practical aeroacoustics problems and to perform numerical simulation of aeroacoustic phenomena. By analysing the simulation data, an investigator can determine noise generation mechanisms and sound propagation processes. This is both a textbook for graduate students and a reference for researchers in CAA and as such is self-contained. No prior knowledge of numerical methods for solving partial differential equations (PDEs) is needed, however, a general understanding of partial differential equations and basic numerical analysis is assumed. Exercises are included and are designed to be an integral part of the chapter content. In addition, sample computer programs are included to illustrate the implementation of the numerical algorithms.



Formulas of Acoustics

Author : F.P. Mechel

Publisher : Springer Science & Business Media

Page : 1197 pages

File Size : 21,7 MB

Release : 2013-06-29

Category : Technology & Engineering

ISBN : 3662072963

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Book Description

This application-orientated collection of formulas has been written by applied scientists and industrial engineers for design professionals and students who work in engineering acoustics. It is subdivided into the most important fields of applied acoustics, each dealing with a well-defined type of problem. It provides easy and rapid access to profound and comprehensive information. In order to keep the text as concise as possible, the derivation of a formula is described as briefly as possible and the reader is referred to the original source. Besides the formulas, useful principles and computational procedures are given.