Time -Accurate Implementation of Lighthill's Acoustic Analogy for Complex 3-D Jet Noise Prediction PDF Download
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Author: Melissa Beth Carter
Publisher:
ISBN:
Category :
Languages : en
Pages : 91
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Author: Melissa Beth Carter
Publisher:
ISBN:
Category :
Languages : en
Pages : 91
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Book Description
Author: Leonardo A. Bueno
Publisher:
ISBN:
Category : FORTRAN (Computer program language)
Languages : en
Pages : 118
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Book Description
"In this thesis, the numerical code for predicting the far-field sound radiated from a localized sound source is developed based on Lighthill's acoustic analogy theory. The acoustic analogy equation allows calculating the sound intensity in terms of the integral over the volume with distributed Lighthill tensor of unsteady flow fluctuations. A FORTRAN code is written to perform the integration using Simpson's numeric technique. The procedure for validating the code against the test case for the sound source in the form of Gaussian pulse is examined. Future application of the code to predict acoustic radiation from turbulent jets is briefly discussed."--Leaf 3.
Author: Stewart Glegg
Publisher: Academic Press
ISBN: 0128097930
Category : Science
Languages : en
Pages : 554
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Book Description
Aeroacoustics of Low Mach Number Flows: Fundamentals, Analysis, and Measurement provides a comprehensive treatment of sound radiation from subsonic flow over moving surfaces, which is the most widespread cause of flow noise in engineering systems. This includes fan noise, rotor noise, wind turbine noise, boundary layer noise, and aircraft noise. Beginning with fluid dynamics, the fundamental equations of aeroacoustics are derived and the key methods of solution are explained, focusing both on the necessary mathematics and physics. Fundamentals of turbulence and turbulent flows, experimental methods and numerous applications are also covered. The book is an ideal source of information on aeroacoustics for researchers and graduate students in engineering, physics, or applied math, as well as for engineers working in this field. Supplementary material for this book is provided by the authors on the website www.aeroacoustics.net. The website provides educational content designed to help students and researchers in understanding some of the principles and applications of aeroacoustics, and includes example problems, data, sample codes, course plans and errata. The website is continuously being reviewed and added to. Explains the key theoretical tools of aeroacoustics, from Lighthill’s analogy to the Ffowcs Williams and Hawkings equation Provides detailed coverage of sound from lifting surfaces, boundary layers, rotating blades, ducted fans and more Presents the fundamentals of sound measurement and aeroacoustic wind tunnel testing
Author: Harvey H. Hubbard
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 620
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Book Description
Author: Vasileios Sassanis
Publisher:
ISBN:
Category :
Languages : en
Pages : 157
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Book Description
In Computational aeroacoustics, hybrid approaches first resolve the source and nearfield regions of the flow field by employing Reynolds Averaged Navier-Stokes (RANS) equations, Large Eddy Simulations (LES) or Direct Numerical Simulations (DNS). The source region data is used to form source terms, which are, in turn, applied to either empirical models or equations linearized around a mean flow. An acoustic analogy type of model is used to propagate the acoustics to the farfield regions. The aim of this research is two-fold: to introduce and test a hybrid acoustic analogy, based on a coupling between the Navier-Stokes equations, applied in the source region, and the Non-linear Euler (NLE) equations applied in the acoustic propagation region; and to test and validate a recently derived generalized acoustic analogy theory in the framework of jet noise with acoustic source information obtained from RANS or LES. In the first part, the coupling between the Navier-Stokes and the NLE equations is accomplished via a buffer region, which is used to interpolate and penalize the flow variables of interest from the source region. The penalized flow variables are then applied as source terms in the NLE equations, to calculate the acoustic propagation. The non-linear Euler equations, discretized using high-accurate dispersion-relation preserving schemes constitute a very efficient approach for jet noise predictions in complex environments, especially for supersonic and hypersonic jets, where nonlinearities may propagate over long distances. In the second part, a RANS- or LES-informed model, which is used to provide data for Goldstein’s generalized acoustic analogy, is presented. The generalized acoustic analogy of Goldstein is considered, wherein the effects of non-parallelism are taken into account and an asymptotic expansion is utilized to simplify the adjoint Green function equations. The use of the adjoint Green’s function leads to a simple model for jet noise predictions for low frequencies and small observation angles, in the linear regime. Both approaches are extensively tested and validated against numerous benchmark problems and applications.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In Computational aeroacoustics, hybrid approaches first resolve the source and nearfield regions of the flow field by employing Reynolds Averaged Navier-Stokes (RANS) equations, Large Eddy Simulations (LES) or Direct Numerical Simulations (DNS). The source region data is used to form source terms, which are, in turn, applied to either empirical models or equations linearized around a mean flow. An acoustic analogy type of model is used to propagate the acoustics to the farfield regions. The aim of this research is two-fold: to introduce and test a hybrid acoustic analogy, based on a coupling between the Navier-Stokes equations, applied in the source region, and the Non-linear Euler (NLE) equations applied in the acoustic propagation region; and to test and validate a recently derived generalized acoustic analogy theory in the framework of jet noise with acoustic source information obtained from RANS or LES. In the first part, the coupling between the Navier-Stokes and the NLE equations is accomplished via a buffer region, which is used to interpolate and penalize the flow variables of interest from the source region. The penalized flow variables are then applied as source terms in the NLE equations, to calculate the acoustic propagation. The non-linear Euler equations, discretized using high-accurate dispersion-relation preserving schemes constitute a very efficient approach for jet noise predictions in complex environments, especially for supersonic and hypersonic jets, where nonlinearities may propagate over long distances. In the second part, a RANS- or LES-informed model, which is used to provide data for Goldstein's generalized acoustic analogy, is presented. The generalized acoustic analogy of Goldstein is considered, wherein the effects of non-parallelism are taken into account and an asymptotic expansion is utilized to simplify the adjoint Green function equations. The use of the adjoint Green's function leads to a simple model for jet
Author:
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 776
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Book Description
Author: Andrea D. Jones
Publisher:
ISBN: 9780549041023
Category : Airplanes
Languages : en
Pages : 87
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Book Description
Aircraft airframe noise pollution resulting from the take-off and landing of airplanes is a growing concern. Because of advances in numerical analysis and computer technology, most of the current noise prediction methods are computationally efficient. However, the ability to effectively apply an approach to complex airframe geometries continues to challenge researchers. The objective of this research is to develop and analyze a robust noise prediction method for dealing with geometrical modifications. This new approach for determining sound pressure involves computing exact, or tailored, Green's functions for use in acoustic analogy. The effects of sound propagation and scattering by solid surfaces are included in the exact Green's function, which is tailored for a specific geometry. The exact Green's function is computed using a spectral collocation boundary element method that can easily accommodate complex geometries. A frequency-domain spectral collocation method is applied to both smooth and non-smooth boundaries, resulting in exponential convergence on smooth boundaries. Solution singularities at boundary corners are dealt with via an exponential grading element refinement. With proper refinement, exponential convergence is also obtained for non-smooth boundaries. The formulation and application of a three-dimensional time-domain BEM allows computation of exact Green's functions for all frequencies in a single calculation. Long-time instabilities in the time-marching numerical solutions are corrected via a Burton-Miller modified integral equation. Two examples provide validation of the acoustic analogy involving the exact Green's function.
Author: F.P. Mechel
Publisher: Springer Science & Business Media
ISBN: 3662072963
Category : Technology & Engineering
Languages : en
Pages : 1197
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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.
Author: Xiaofeng Sun
Publisher: Elsevier
ISBN: 012408074X
Category : Technology & Engineering
Languages : en
Pages : 556
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Book Description
Fundamentals of Aeroacoustics with Applications to Aeropropulsion Systems from the Shanghai Jiao Tong University Press Aerospace series, is the go-to reference on the topic, providing a modern take on the fundamental theory and applications relating to prediction and control of all major noise sources in aeropropulsion systems. This important reference compiles the latest knowledge and research advances, considering both the physics of aerodynamic noise generation in aero-engines and related numerical prediction techniques. Additionally, it introduces new vortex sound interaction models, a transfer element method, and a combustion instability model developed by the authors. Focusing on propulsion systems from inlet to exit, including combustion noise, this new resource will aid graduate students, researchers, and R&D engineers in solving the aircraft noise problems that currently challenge the industry. Updates the knowledge-base on the sound source generated by aeropropulsion systems, from inlet to exit, including combustion noise Covers new aerodynamic noise control technology aimed at the low-noise design of next generation aero-engines, including topics such as aerodynamic noise and aero-engine noise control Includes new, cutting-edge models and methods developed by an author team led by the editor-in-chief of the Chinese Journal of Aeronautics and Astronautics Considers both the physics of aerodynamic noise generation in aero-engines and related numerical prediction techniques
