Download or read book Acoustic Control of Turbulent Jets written by A.S. Ginevsky and published by Springer Science & Business Media. This book was released on 2012-11-02 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of experimental research on aerodynamic and acoustic control of subsonic turbulent jets by acoustic excitation are presented. It was demonstrated that these control methods, originated by authors, not only can intensify mixing (by acoustic irradiation at low frequency), but also notably ease it (at high-frequency irradiation). This research monograph presents the updated results of the authors supplemented by other investigations conducted in USA, Germany and Great Britain. The methods for the numerical simulation of subsonic turbulent jets under acoustic excitation are described in detail, and examples are reviewed of practical applications, including reduction of turbojet engine noise and acoustic control of self-sustained oscillations in wind tunnels.

Download or read book An Acoustic Source Modeling Technique to Predict the Near Sound Field of Axisymmetric Turbulent Jets written by Sundaram C. Venkitarama and published by . This book was released on 1981 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Flow Control written by and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary purpose of this project was to explore actuators, sensors, and control strategies for active control of turbulent jets and boundary layers. Potential applications of this work are to boundary layer control in aircraft and propulsion systems, which should be enabled by concurrent developments in MEMS fabrication technology. The present experiments were performed in a low-speed water flow, where the turbulence is large scale and slow, allowing easy measurement of flow properties and use of actuators and sensors that could be fabricated individually. A zero net mass flow actuator was developed and used in conjunction with wall stress sensors to demonstrate control of laminar flows containing steady and unsteady streamwise vorticies similar to those found in the near-wall region of turbulent boundary layers. Various closed loop control schemes, including an adaptive inverse neural net control, were explored. An early phase of the project was devoted to extension of work on control of round jets by acoustic excitation. It was shown that the jet direction and mixing can be strongly influenced by acoustic and fluidic actuation.

Download or read book Visualization of Conventional and Combusting Subsonic Jet Instabilities written by Victor V. Kozlov and published by Springer. This book was released on 2015-11-30 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on new information obtained on free microjets, this book explains the latest phenomena in flame evolution in the presence of a transverse acoustic field with round and plane propane microjet combustion. It gives an overview of recent experimental results on instability and dynamics of jets at low Reynolds numbers and provides the reader, step by step, with the milestones and recent advances in jet flow stability and combustion. Readers will also discover a clarification of the differences between top-hat and parabolic round and plane jet instability. Chapters demonstrate features of the interaction between jet and crossflow, and how experimental data testify to similarities of the perturbed flow patterns of laminar and turbulent round jets. A similar response of the jets to external acoustic oscillations is shown, as well as the peculiarities of the effect of a transverse acoustic field on downstream evolution of round and plane macro- and microjets. Basic features of round and plane, macro and micro jets' evolution affected by initial conditions at the nozzle outlet and by environmental perturbations are highlighted. Students of fluid mechanics will gain a solid foundation in hydrodynamic stability and combustion of subsonic jet flow and researchers will value the presentation of special aspects of instability and transition. The work treats both theoretical and practical facets, and it includes supplementary material such as PowerPoint multimedia notes based on results of laboratory scientific experiments.

Download or read book Numerical Simulation of Turbulent Flows and Noise Generation written by Christophe Brun and published by Springer Science & Business Media. This book was released on 2009-03-07 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large Eddy Simulation (LES) is a high-fidelity approach to the numerical simulation of turbulent flows. Recent developments have shown LES to be able to predict aerodynamic noise generation and propagation as well as the turbulent flow, by means of either a hybrid or a direct approach. This book is based on the results of two French/German research groups working on LES simulations in complex geometries and noise generation in turbulent flows. The results provide insights into modern prediction approaches for turbulent flows and noise generation mechanisms as well as their use for novel noise reduction concepts.

Download or read book Transition and Turbulence Control written by Mohamed Gad-el-Hak and published by World Scientific. This book was released on 2006 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains articles based on lectures given at the Workshop on Transition and Turbulence Control, hosted by the Institute for Mathematical Sciences, National University of Singapore, 8-10 December 2004. The lecturers included 13 of the world's foremost experts in the control of transitioning and turbulent flows. The chapters cover a wide range of subjects in the broad area of flow control, and will be useful to researchers working in this area in academia, government laboratories and industry. The coverage includes control theory, passive, active and reactive methods for controlling transitional and turbulent wall-bounded flows, noise suppression and mixing enhancement of supersonic turbulent jets, compliant coatings, modern flow diagnostic systems, and swept wing instabilities.

Download or read book Fundamental Study of Jet Noise Generation and Suppression written by W. C. Sperry and published by . This book was released on 1961 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Flow Control written by and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary purpose of this project was to explore actuators, sensors, and control strategies for active control of turbulent jets and boundary layers. Potential applications of this work are to boundary layer control in aircraft and propulsion systems, which should be enabled by concurrent developments in MEMS fabrication technology. The present experiments were performed in a low-speed water flow, where the turbulence is large scale and slow, allowing easy measurement of flow properties and use of actuators and sensors that could be fabricated individually. A zero net mass flow actuator was developed and used in conjunction with wall stress sensors to demonstrate control of laminar flows containing steady and unsteady streamwise vorticies similar to those found in the near-wall region of turbulent boundary layers. Various closed loop control schemes, including an adaptive inverse neural net control, were explored. An early phase of the project was devoted to extension of work on control of round jets by acoustic excitation. It was shown that the jet direction and mixing can be strongly influenced by acoustic and fluidic actuation.

Download or read book Physics of Turbulent Jet Ignition written by Sayan Biswas and published by Springer. This book was released on 2018-05-03 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on developing strategies for ultra-lean combustion of natural gas and hydrogen, and contributes to the research on extending the lean flammability limit of hydrogen and air using a hot supersonic jet. The author addresses experimental methods, data analysis techniques, and results throughout each chapter and: Explains the fundamental mechanisms behind turbulent hot jet ignition using non-dimensional analysis Explores ignition characteristics by impinging hot jet and multiple jets in relation to better controllability and lean combustion Explores how different instability modes interact with the acoustic modes of the combustion chamber. This book provides a potential answer to some of the issues that arise from lean engine operation, such as poor ignition, engine misfire, cycle-to-cycle variability, combustion instability, reduction in efficiency, and an increase in unburned hydrocarbon emissions. This thesis was submitted to and approved by Purdue University.

Download or read book Acoustic Effect on Aerodynamic Characteristics of a Turbulent Jet written by E. V. Vlasov and published by . This book was released on 1968 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was made of the effect of sound of various intensities and frequencies on the mean and pulsating flow characteristics of a submerged turbulent jet. It was shown that at a certain sound intensity and frequency it is possible either to intensify or attenuate turbulent mixing. In general, a low frequency sound increased the mixing process. An attenuation of the turbulent mixing process was noted in the presence of a high frequency sound and relatively low Reynolds numbers.

Download or read book Handbook of Noise and Vibration Control written by Malcolm J. Crocker and published by John Wiley & Sons. This book was released on 2007-10-05 with total page 1594 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two of the most acclaimed reference works in the area of acoustics in recent years have been our Encyclopedia of Acoustics, 4 Volume set and the Handbook of Acoustics spin-off. These works, edited by Malcolm Crocker, positioned Wiley as a major player in the acoustics reference market. With our recently published revision of Beranek & Ver's Noise and Vibration Control Engineering, Wiley is a highly respected name in the acoustics business. Crocker's new handbook covers an area of great importance to engineers and designers. Noise and vibration control is one largest areas of application of the acoustics topics covered in the successful encyclopedia and handbook. It is also an area that has been under-published in recent years. Crocker has positioned this reference to cover the gamut of topics while focusing more on the applications to industrial needs. In this way the book will become the best single source of need-to-know information for the professional markets.

Download or read book FY US Air Force Plan for Defense Research Sciences written by and published by . This book was released on 1983 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeroacoustics of Flight Vehicles written by Harvey H. Hubbard and published by . This book was released on 1991 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Noise Produced by an Orderly Structure of Turbulent Jets written by Jay C. Hardin and published by . This book was released on 1973 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The orderly structure which has been observed recently by numerous researchers within the transition region of subsonic turbulent jets is analyzed to reveal its noise-producing potential. For a circular jet, this structure is molded as a train of toroidal vortex rings which are formed near the jet exit and propagate downstream. The noise produced by the model is evaluated from a reformulation of Lighthill's expression for the far-field acoustic density, which emphasizes the importance of the vorticity within the turbulent flow field. It is shown that the noise production occurs mainly close to the jet exit and depends primarily upon temporal changes in the toroidal radii. The analysis suggests that the process of formation of this regular structure may also be an important contribution of the high-frequency jet noise. These results may be helpful in the understanding of jet-noise generation and in new approaches to jet-noise suppression.

Download or read book Modern Developments in Shear Flow Control with Swirl written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-29 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Passive and active control of swirling turbulent jets is experimentally investigated. Initial swirl distribution is shown to dominate the free jet evolution in the passive mode. Vortex breakdown, a manifestation of high intensity swirl, was achieved at below critical swirl number (S = 0.48) by reducing the vortex core diameter. The response of a swirling turbulent jet to single frequency, plane wave acoustic excitation was shown to depend strongly on the swirl number, excitation Strouhal number, amplitude of the excitation wave, and core turbulence in a low speed cold jet. A 10 percent reduction of the mean centerline velocity at x/D = 9.0 (and a corresponding increase in the shear layer momentum thickness) was achieved by large amplitude internal plane wave acoustic excitation. Helical instability waves of negative azimuthal wave numbers exhibit larger amplification rates than the plane waves in swirling free jets, according to hydrodynamic stability theory. Consequently, an active swirling shear layer control is proposed to include the generation of helical instability waves of arbitrary helicity and the promotion of modal interaction, through multifrequency forcing. Farokhi, Saeed and Taghavi, R. Unspecified Center NCC3-56...

Download or read book Optimization and Modeling of Noise Reduction for Turbulent Jets with Induced Asymmetry written by Sara Rostamimonjezi and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project relates to the development of next-generation high-speed aircraft that are efficient and environmentally compliant. The emphasis of the research is on reducing noise from high-performance engines that will power these aircraft. A strong component of engine noise is jet mixing noise that comes from the turbulent mixing process between the high-speed exhaust flow of the engine and the atmosphere. The fan flow deflection method (FFD) suppresses jet noise by deflecting the fan stream downward, by a few degrees, with respect to the core stream. This reduces the convective Mach number of the primary shear layer and turbulent kinetic energy in the downward direction and therefore reduces the noise emitted towards the ground. The redistribution of the fan stream is achieved with inserting airfoil-shaped vanes inside the fan duct. Aerodynamic optimization of FFD has been done by Dr. Juntao Xiong using a computational fluid dynamics code to maximize reduction of noise perceived by the community while minimizing aerodynamic losses. The optimal vane airfoils are used in a parametric experimental study of 50 4-vane deflector configurations. The vane chord length, angle of attack, and azimuthal location are the parameters studied in acoustic optimization. The best vane configuration yields a reduction in cumulative (downward + sideline) effective perceived noise level (EPNL) of 5.3 dB. The optimization study underscores the sensitivity of FFD to deflector parameters and the need for careful design in the practical implementation of this noise reduction approach. An analytical model based on Reynolds Averaged Navier Stokes (RANS) and acoustic analogy is developed to predict the spectral changes from a known baseline in the direction of peak emission. A generalized form for space-time correlation is introduced that allows shapes beyond the traditional exponential forms. Azimuthal directivity based on the wavepacket model of jet noise is integrated with the acoustic analogy model. A physics-based definition of convective Mach number is proposed. The predicted noise reduction is in reasonable agreement with the experiments. The study underscores the importance of a proper definition of convective Mach number when modeling noise in the direction of peak emission.

Download or read book Handbook of Acoustics written by Malcolm J. Crocker and published by John Wiley & Sons. This book was released on 1998-03-09 with total page 1494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustical engineers, researchers, architects, and designers need a comprehensive, single-volume reference that provides quick and convenient access to important information, answers and questions on a broad spectrum of topics, and helps solve the toughest problems in acoustical design and engineering. The Handbook of Acoustics meets that need. It offers concise coverage of the science and engineering of acoustics and vibration. In more than 100 clearly written chapters, experts from around the world share their knowledge and expertise in topics ranging from basic aerodynamics and jet noise to acoustical signal processing, and from the interaction of fluid motion and sound to infrasound, ultrasonics, and quantum acoustics. Topics covered include: * General linear acoustics * Nonlinear acoustics and cavitation * Aeroacoustics and atmospheric sound * Mechanical vibrations and shock * Statistical methods in acoustics * Architectural acoustics * Physiological acoustics * Underwater sound * Ultrasonics, quantum acoustics, and physical aspects of sound * Noise: its effects and control * Acoustical signal processing * Psychological acoustics * Speech communication * Music and musical acoustics * Acoustical measurements and instrumentation * Transducers The Handbook of Acoustics belongs on the reference shelf of every engineer, architect, research scientist, or designer with a professional interest in the propagation, control, transmission, and effects of sound.