Download or read book Analysis and Discretization of Time Domain Impedance Boundary Conditions in Aeroacoustics written by Florian Monteghetti and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In computational aeroacoustics, time-domain impedance boundary conditions (TDIBCs) canbe employed to model a locally reacting sound absorbing material. They enable to computethe effect of a material on the sound field after a homogenization distance and have proveneffective in noise level predictions. The broad objective of this work is to study the physical,mathematical, and computational aspects of TDIBCs, starting from the physical literature.The first part of this dissertation defines admissibility conditions for nonlinear TDIBCs underthe impedance, admittance, and scattering formulations. It then shows that linear physicalmodels, whose Laplace transforms are irrational, admit in the time domain a time-delayedoscillatory-diffusive representation and gives its physical interpretation. This analysis enablesto derive the discrete TDIBC best suited to a particular physical model, by contrast with a onesize-fits-all approach, and suggests elementary ways of computing the poles and weights. Theproposed time-local formulation consists in composing a set of ordinary differential equationswith a transport equation.The main contribution of the second part is the proof of the asymptotic stability of the multidimensionalwave equation coupled with various classes of admissible TDIBCs, whose Laplacetransforms are positive-real functions. The method of proof consists in formulating an abstractCauchy problem on an extended state space using a realization of the impedance, be it finiteor infinite-dimensional. The asymptotic stability of the corresponding strongly continuoussemigroup of contractions is then obtained by verifying the sufficient spectral conditions of theArendt-Batty-Lyubich-V ̃u theorem.The third and last part of the dissertation tackles the discretization of the linearized Eulerequations with TDIBCs. It demonstrates the computational advantage of using the scatteringoperator over the impedance and admittance operators, even for nonlinear TDIBCs. This isachieved by a systematic semi-discrete energy analysis of the weak enforcement of a genericnonlinear TDIBC in a discontinuous Galerkin finite element method. In particular, the analysishighlights that the sole definition of a discrete model is not enough to fully define a TDIBC.To support the analysis, an elementary physical nonlinear scattering operator is derived andits computational properties are investigated in an impedance tube. Then, the derivation oftime-delayed broadband TDIBCs from physical reflection coefficient models is carried out forsingle degree of freedom acoustical liners. A high-order discretization of the derived time-localformulation, which consists in composing a set of ordinary differential equations with a transportequation, is applied to two flow ducts.
Download or read book Time domain Impedance Boundary Condition for Computational Aeroacoustics written by Christopher K. W. Tam and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Liner Impedance Modeling in the Time Domain with Flow written by Christoph Richter and published by Univerlagtuberlin. This book was released on 2009 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Impedance Boundary Conditions for Time domain Computational Aeroacoustics Methods written by Yusuf Ozyoruk and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Implementation of a Time Domain Impedance Boundary Condition written by Qiuling Suo and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Trailing edge noise is an important source of airframe noise. It is mainly caused by the turbulent pressure fluctuations passing an edge discontinuity. A promising passive modification for noise reduction is to use porous or partly porous airfoils. Some of the numerical studies of the porous airfoils focus on describing the complete phenomenon. The flow inside the porous region is investigated separately from the outside flow field. However, this is often computationally demanding and time consuming. For engineering purposes, a gross description of the effects of the impedance materials on incident acoustic waves is preferred. The method of time-domain impedance boundary condition is attractive to study noise scattering of absorbing surfaces. The acoustic impedance is used to describe the properties of an absorbing material. It is defined in the frequency domain as the ratio of the acoustic pressure to the acoustic velocity normal to the porous or impedance surface. Most classical impedance models were obtained in the frequency domain, and to obtain a time domain impedance boundary condition is not straightforward. In this thesis, a three-parameter model based on the mass-spring-damper system is adopted. It is verified to have a stable solution. The key to the implementation of this model is to use a ghost point outside the computational domain. This ensures that the boundary points satisfy both the discretized Euler equations and the absorbing boundary condition. Numerical results for the normal-incidence impedance tube problems show a good agreement with the analytical results. The time domain impedance boundary condition has also been developed into a two-dimensional form. An initial example problem is a Gaussian pressure pulse propagating in a uniform Cartesian grid. After that, the simulation is modified into the curvilinear coordinates to simulate the acoustic scattering around a circular cylinder. The results qualitatively show that the absorbing boundaries do reduce the amplitude of the reflected pulse. Having demonstrated simulations for a curved surface, the time domain impedance boundary condition is applied to an impedance-treated airfoil. This code could be used to find a better design of the geometry of the porous trailing edge, and to provide a better choice of the properties of the impedance.
Download or read book A Comparison of Time Domain Boundary Conditions for Acoustic Waves in Wave Guides written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1991 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Aeroacoustics written by Christopher K. W. Tam and published by Cambridge University Press. This book was released on 2012-09-28 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Computational Strategies for Impedance Boundary Condition Integral Equations in Frequency and Time Domains written by Alexandre Dély and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Boundary Elements in Acoustics written by Otto von Estorff and published by Computational Mechanics. This book was released on 2000 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text provides reports on all aspects of BEM calculations in acoustics. Special attention is paid to efficiency and accuracy issues, frequency and time domain procedures, direct and indirect formulations, hybrid as well as inverse techniques. Emphasis is also placed on applications in different firlds, such as vehicle acoustics, engine noise, electroacoustic transducers, optimization of musical instruments and underwater acoustics.
Download or read book Wideband Impedance Boundary Conditions for FE DG Methods for Solving Maxwell Equations in Time Domain written by Irene Woyna and published by . This book was released on 2014 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1996 with total page 834 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Boundary Element Method in Acoustics written by Stephen Kirkup and published by Stephen Kirkup. This book was released on 1998 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Broadband Time domain Impedance Boundary Modeling with the Discontinuous Galerkin Method for Room Acoustics Simulations written by Huiqing Wang and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2004 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Finite Element and Boundary Methods in Structural Acoustics and Vibration written by Noureddine Atalla and published by CRC Press. This book was released on 2015-04-17 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effectively Construct Integral Formulations Suitable for Numerical ImplementationFinite Element and Boundary Methods in Structural Acoustics and Vibration provides a unique and in-depth presentation of the finite element method (FEM) and the boundary element method (BEM) in structural acoustics and vibrations. It illustrates the principles using a
Download or read book Acoustics of Ducts and Mufflers written by M. L. Munjal and published by John Wiley & Sons. This book was released on 2014-02-04 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fully updated second edition of the premier reference book on muffler and lined duct acoustical performance Engine exhaust noise pollutes the street environment and ventilation fan noise enters dwellings along with fresh air. People have become conscious of their working environment. Governments of most countries have responded to popular demand with mandatory restrictions on sound emitted by automotive engines, and a thorough knowledge of acoustics of ducts and mufflers is needed for the design of efficient muffler configurations. This fully updated Second Edition of Acoustics of Ducts and Mufflers deals with propagation, reflection and dissipation/absorption of sound along ducts/pipes/tubes, area discontinuities, perforated elements and absorptive linings that constitute the present-day mufflers and silencers designed to control noise of exhaust and intake systems of automotive engines, diesel-generator sets, compressors and HVAC systems. It includes equations, figures, tables, references, and solved examples and unsolved exercises with answers, so it can be used as a text book as well as a reference book. It also offers a complete presentation and analysis of the major topics in sound suppression and noise control for the analysis and design of acoustical mufflers, air conditioning and ventilation duct work. Both the fundamentals and the latest technology are discussed, with an emphasis on applications. Deals with reactive mufflers, dissipative silencers, the frequency-domain approach, and the time-domain approach. Fully updated second edition of the premier reference book on muffler and lined duct acoustical performance, in one complete volume Presents original new research on topics including baffle silencers and louvers, 3D analytical techniques, and flow-acoustic analysis of multiply-connected perforated-element mufflers Includes a general design procedure to help muffler designers in the automotive industry, exhaust noise being a major component of automobile and traffic noise pollution Written by an expert with four decades’ experience in teaching to graduate students, publishing extensively in reputed international journals, and consulting with industry for noise control as well as designing for quietness
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
