Simulation of Sound Propagation Through High-resolution Atmospheric Boundary Layer Turbulence Fields PDF Download

Author:
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 6

View

Book Description

Author: Jean-Baptiste Blanc
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 158

View

Book Description
Boundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of the turbulence with uncorrelated sheets of vorticity. Both aerodynamic and acoustic results are compared to experimental measurements of the flow. The CFD simulation of the flow returns consistent results but would benefit from a refinement of the grid. The surface pressure spectrum presents a slope in the high frequencies close to the experimental spectrum. The far field noise spectrum has a 5dB difference to the experiments.

Author: Roberto Camussi
Publisher: Springer Science & Business Media
ISBN: 3709114586
Category : Technology & Engineering
Languages : en
Pages : 453

View

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.

Author: Acoustical Society of America
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 1042

View

Book Description

Author: Kyong Sang Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 272

View

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10

View

Book Description
In this project, we developed 3D models of temperature and wind velocity fluctuations in nighttime boundary layers (NBL) and, using these models, studied sound propagation and scattering. The 3D spectra of temperature and velocity fluctuations due to internal gravity waves in moderately and very stable NBL were obtained. The 3D spectra of turbulent temperature and wind velocity fluctuations in weakly stable, intermittent NBL were modeled with the use of the von Karman spectra. Quasi-wavelet models of turbulent temperature and velocity fluctuations were developed. The developed models of internal gravity waves, turbulence, and quasi-wavelets were then used for calculations of the statistical moments of plane and spherical sound waves propagating in the atmosphere. These calculations were done for three different problems: scattering of sound, line-of-sight sound propagation, and sound propagation in a refractive, turbulent atmosphere near an impedance ground. The coherence function of a sound field propagating in NBL was measured and compared with that predicted theoretically.

Author: Thomas Rossing
Publisher: Springer Science & Business Media
ISBN: 0387304460
Category : Science
Languages : en
Pages : 1179

View

Book Description
This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17

View

Book Description
In complex environments the modelling of outdoor sound propagation implies to take into account the mixed influence of ground characteristics (topography, obstacles, impedance, etc.) and atmospheric conditions (refraction and turbulence). During the last decade significant progress has been made in the modelling of sound propagation over distances ranging from hundreds meters to kilometres, and the agreement between calculated and measured fields has been greatly improved. New developments appear in the parabolic-equation method. In this paper we present a method which evaluates the propagation of an acoustic wave above uneven terrains including realistic meteorological parameters. In our approach the effects of the topography are modelled using appropriate rotated co-ordinates systems in order to treat the non-flat ground as a succession of flat domains. We also examine the influence of scale resolution on numerical simulation of long range sound propagation through the turbulent atmosphere. Currently, we generate the turbulence using a Random Fourier Modes technique, such that the turbulent fluctuation at any point in the medium (either scalar or vectorial in nature) is calculated from the sum of a chosen number of modes. Our model of outdoors sound propagation is validated both with classical numerical benchmark cases and recent outdoor experiments.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10

View

Book Description
Three-dimensional models of anisotropic and inhomogeneous spectra of temperature and wind velocity fluctuations in unstable atmospheric boundary layers have been developed, modified or extended. Furthermore, theories of sound propagation through anisotropic, inhomogeneous, and intermittent atmospheric turbulence have been developed. These theories allow consideration of different geometries of sound propagation: line-of-sight sound propagation, interference of the direct and ground reflected waves, sound scattering into a refractive shadow zone, and waveguide sound propagation. Using the spectra developed or adopted from the literature, it was shown that anisotropy, inhomogeneity, and intermittency of atmospheric turbulence can significantly affect the statistical moments of a sound field for these geometries. Some of the theoretical results obtained have been verified experimentally. Two related tasks have also been accomplished. First, a new scheme of source localization in the atmosphere by means of acoustic tomography was proposed. The scheme accounts for sound refraction in the atmosphere and allows retrieval of vertical profiles of temperature and wind velocity. Secondly, it was shown that, in many cases, the effects of sound refraction on acoustic remote sensing of wind velocity and the structure parameters of temperature and velocity fluctuations are significant. Algorithms were developed to account for these effects in acoustic remote sensing of the atmosphere.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1102

View

Book Description