Author: Birendra DuttPublisher:
ISBN:
Category : Supersonic nozzles
Languages : en
Pages : 208
Book Description
Role of Large Scale Structures in the Noise Generation of a Turbulent Supersonic Jet
Author: Birendra DuttPublisher:
ISBN:
Category : Supersonic nozzles
Languages : en
Pages : 208
Book Description
Large Scale Turbulent Structures in Supersonic Jets
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781722333546
Category :
Languages : en
Pages : 34
Book Description
Jet noise is a major concern in the design of commercial aircraft. Studies by various researchers suggest that aerodynamic noise is a major contributor to jet noise. Some of these studies indicate that most of the aerodynamic jet noise due to turbulent mixing occurs when there is a rapid variation in turbulent structure, i.e. rapidly growing or decaying vortices. The objective of this research was to simulate a compressible round jet to study the non-linear evolution of vortices and the resulting acoustic radiations. In particular, to understand the effect of turbulence structure on the noise. An ideal technique to study this problem is Direct Numerical Simulations (DNS), because it provides precise control on the initial and boundary conditions that lead to the turbulent structures studied. It also provides complete 3-dimensional time dependent data. Since the dynamics of a temporally evolving jet are not greatly different from those of a spatially evolving jet, a temporal jet problem was solved, using periodicity in the direction of the jet axis. This enables the application of Fourier spectral methods in the streamwise direction. 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. The DNS jet simulation helps us understand the various turbulent scales and mechanisms of turbulence generation in the evolution of a compressible round jet. These accurate flow solutions will be used in future research to estimate near-field acoustic radiation by computing the total outward flux across a surface and determine how it is related to the evolution of the turbulent solutions. Furthermore, these simulations allow us to investigate the sensitivity of acoustic radiations to inlet/boundary conditions, with possible appli(, a- tion to active noise suppression. In addition, the data generated can be used to compute, various turbulence quantities such as mean velociti..
Coherent Large-scale Structures in High Reynolds Number Supersonic Jets
Author: J. LepicovskyPublisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 112
Book Description
The flow structure of a 50.8 mm (2 in) diameter jet operated at a full expanded Mach number of 1.37, with Reynolds numbers in the range 1.7 to 2.35 million, was examined for the first 20 jet diameters. To facilitate the study of the large scale structure, and determine any coherence, a discrete tone acoustic excitation method was used. Phase locked flow visualization as well as laser velocimeter quantitative measurements were made. The main conclusions derived from this study are: (1) large scale coherent like turbulence structures do exist in large Reynolds number supersonic jets, and they prevail even beyond the potential core; (2) the most preferential Strouhal number for these structures is in the vicinity of 0.4; and (3) quantitatively, the peak amplitudes of these structures are rather low, and are about 1% of the jet exit velocity. Finally, since a number of unique problems related to LV measurements in supersonic jets were encountered, a summary of these problems and lessons learned therefrom are also reported.
Noise Sources in Turbulent Shear Flows: Fundamentals and Applications
Author: Roberto CamussiPublisher: Springer Science & Business Media
ISBN: 3709114586
Category : Technology & Engineering
Languages : en
Pages : 453
Book Description
The articles in this volume present the state-of-the-art in noise prediction, modeling and measurement. The articles are partially based on class notes provided during the course `Noise sources in turbulent shear flows', given at CISM on April 2011. The first part contains general concepts of aero acoustics, including vortex sound theory and acoustic analogies, in the second part particular emphasis is put into arguments of interest for engineers and relevant for aircraft design: jet noise, airfoil broadband noise, boundary layer noise (including interior noise and its control) and the concept of noise sources, their theoretical modeling and identification in turbulent lows. All these arguments are treated extensively with the inclusion of many practical examples and references to engineering applications.
The Generation, Radiation and Prediction of Supersonic Jet Noise
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 509
Book Description
The work presented in this report forms a continuation of the fundamental studies on the generation and radiation of supersonic jet noise, reported in technical reports AFAPL-TR-72-53 (six volumes), AFAPL-TR-74-24, and AFAPL-TR-76-65 (four volumes). The total noise from a supersonic jet is taken to consist of contributions from three independent noise sources: (1) small-scale turbulent mixing noise, (2) noise from large-scale turbulence structure, and (3) shock-associated noise. The generation, radiation and prediction of each of these noise components is described in this report. In addition, the mean and turbulent flow characteristics of heated and unheated, subsonic and supersonic jets, measured by a laser velocimeter system, are also presented. Finally, a computer program for the prediction of jet noise, based on fundamental principles as far as possible at the present time, is presented and described in the form of a user's guide. A complete listing of this computer program is given in the Appendix volume (Volume 11) of this report.
Supersonic Jet Noise Generated by Large-scale Instabilities
Author: John M. SeinerPublisher:
ISBN:
Category : Jet planes
Languages : en
Pages : 52
Book Description
Supersonic Jet Noise Generated by Large-scale Instabilities
Author: John M. SeinerPublisher:
ISBN:
Category : Jet planes
Languages : en
Pages : 52
Book Description
The Generation and Radiation of Supersonic Jet Noise. Volume 2. Studies of Jet Noise, Turbulence Structure and Laser Velocimetry
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 460
Book Description
This volume discusses (1) turbulent mixing noise tests and observations relative to effects of temperature and Mach number on intensity, directivity, and spectra; (2) numerical solutions of the Lilley theory for sound radiated from point sources simulating small-scale turbulence noise sources, and comparisons of these solutions with experimental data relating to temperature and velocity effects on directivity and spectra; (3) the theory describing the development of the large-scale coherent motion of the jet structure and the far- field noise radiated from this turbulence; (4) a detailed discussion and interpretation of the jet turbulence and mean velocity data; and (5) a comprehensive description of the shock-associated noise tests, a preliminary description of the broadband shock-associated noise model, and a discussion of shock-associated noise in the overall jet noise picture.
Aeroacoustics of Flight Vehicles
Author: Harvey H. HubbardPublisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 620
Book Description
Author: