Download or read book Emission of Sound from Turbulence Convected by a Parallel Mean Flow in the Presence of a Confining Duct written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-05-31 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: An approximate method for calculating the noise generated by a turbulent flow within a semi-infinite duct of arbitrary cross section is developed. It is based on a previously derived high-frequency solution to Lilley's equation, which describes the sound propagation in transversely-sheared mean flow. The source term is simplified by assuming the turbulence to be axisymmetric about the mean flow direction. Numerical results are presented for the special case of a ring source in a circular duct with an axisymmetric mean flow. They show that the internally generated noise is suppressed at sufficiently large upstream angles in a hard walled duct, and that acoustic liners can significantly reduce the sound radiated in both the upstream and downstream regions, depending upon the source location and Mach number of the flow.Goldstein, Marvin E. and Leib, Stewart J.Glenn Research CenterSOUND PROPAGATION; EMISSION; COMPUTATION; TURBULENT FLOW; APPROXIMATION; UPSTREAM; TURBULENCE; SHEAR FLOW; MACH NUMBER; LININGS; DUCTS; AXISYMMETRIC FLOW

Download or read book Emission of Sound From Turbulence Convected by a Parallel Mean Flow in the Presence of a Confining Duct written by and published by . This book was released on 1999 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Emission of Sound from Turbulence Convected by a Parallel Flow in the Presence of Solid Boundaries written by Marvin E. Goldstein and published by . This book was released on 1973 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical description is given of the sound emitted from an arbitrary point in a parallel or nearly parallel turbulent shear flow confined to a region near solid boundaries. The analysis begins with Lighthill's formulation of aerodynamic noise and assumes that the turbulence is axisymmetric. Specific results are obtained for the sound emitted from an arbitrary point in a turbulent flow within a semi-infinite, open-ended duct.

Download or read book Emission of Sound from Turbulence Convected by a Parallel Flow in the Presence of Solid Boundaries written by Marvin E. Goldstein and published by . This book was released on 1973 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sound from Turbulence Convected by a Parallel Flow Within a Rectangular Duct written by S. J. Leib and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Institute for Computational Mechanics in Propulsion ICOMP written by and published by . This book was released on 2001 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 2000 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Emission of Sound from Axisymmetric Turbulence Convected by a Mean Flow with Apllication to Jet Noise written by Marvin E. Goldstein and published by . This book was released on 1972 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanics written by and published by . This book was released on 2001 with total page 422 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 2001 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow Acoustic Interaction in Duct Inflow written by M. C. Quinn and published by . This book was released on 1987 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sound generation in the convection of turbulence into a flow intake duct is discussed by examination of an idealised problem. Ideal fluid is in motion with uniform low, subsonic velocity above and parallel to a plane, rigid wall. A thin, rigid, semi-infinite plate is parallel to the wall and the fluid flows past its leading edge. The radiated sound is calculated for a turbulent eddy modelled by a weak line vortex which is allowed to convect passively past the leading edge of the plate. Account is taken of the contribution to the radiated sound from the disturbance produced by the convecting vortex in the boundary layers on each side of the plate by means of Howe's (1981) theory of displacement thickness fluctuations, the strength of the disturbance being fixed by a leading edge Kutta condition. It is concluded that the predicted level of the radiated sound is substantially reduced due to the boundary layer disturbances relative to when they are neglected. The case of the convection of a frozen two-dimensional gust is also considered. Examination of the analogous problem of plane wave radiation from the duct shows that the presence of displacement waves enhanced both the far-field intensity in the ambient fluid and the reflected field within the duct.

Download or read book The Journal of the Acoustical Society of America written by Acoustical Society of America and published by . This book was released on 2001 with total page 1654 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Shock and Vibration Digest written by and published by . This book was released on 2001 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Emission of Sound from Axisymmetric Turbulence by a Mean Flow with Application to Jet Noise written by Marvin E. Goldstein and published by . This book was released on 1972 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interaction Between Air Flow and Airborne Sound in a Duct written by Fridolin P. Mechel and published by . This book was released on 1965 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several studies of the interaction between air flow and airborne sound in a duct were made. Three projects were investigated: (1) The excitation of boundary layer distortions in a laminar boundary layer by simulated oscillatory flexural waves was investigated. Results show boundary layer waves are excited whenever the phase velocity of the flexure wave is in the instability range of the phase velocity of boundary layer waves. (2) The propagation of a pressure pulse wave front and the acoustic impedance of porous absorbers are examined in ducts with air flow. Measurements prove the sound energy of the wave front is directed towards the walls and the absorber impedance becomes nonlinear when the absorber is penetrated by the flow. (3) the effect on the acoustic radiation impedance of an orifice with flow discharge restricted by fences and diaphragms was investigated. The acoustic resistance was shown to increase at low frequencies due to the restrictions.

Download or read book Study of the Effects of High Intensity Sound on Turbulent Incompressible Flow written by William C. Carlson and published by . This book was released on 1965 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of propagating a sonic disturbance without reflection in a direction parallel but contrary to flow, over the entire flow, were experimentally studied in a 10-cm by 10-cm square duct with a fluid velocity of 6.8 meters per second, or pipe Reynolds number of 4700. The effect was investigated over a range of sound frequencies of 300 to 1800 cps and sound pressure levels of 85 to 140 db re 0.0002 microbars. Sonic excitation reduced the low frequency components (below 300 cps) of the incoming turbulence. The turbulence reduction was greatest for a sound of frequency 700 cps and increased with increasing SPL. This reduction of incoming turbulence appears to retard transition to turbulence by reducing the amount of turbulence in air entering the duct thereby altering the turbulence profile without apparently changing the velocity profile. (Author).

Download or read book Experimental Investigations on the Scattering of Sound by Turbulence written by Dieter W. Schmidt and published by . This book was released on 1961 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental investigations of the scattering of sound by turbulence were performed in a wind tunnel. Turbulence was produced by grids of parallel circular rods (with diameters of 0.1 to 1.0 cm and grid meshlengths of 0.5 to 2. 5 cm); the sound frequencies covered a range of 100 to 500 kc. Disturbances of the measurements due to reflections of sound waves at the tunnel walls were avoided by the application of short sound pulses. The dependence of the damping of the sound waves on the sound frequency, the Mach number of the turbulence, the length of the sound path in the turbulent flow and a predominant direction of the turbulent eddies was measured. Theoretical predictions were confirmed and partly extended. In the range of the parameters which is of interest for practical use the most important results are the proportionality of the damping to the square of the sound frequency and to the square of the turbulent Mach number. Based on the measurements and the theoretical considerations, a formula is derived which is applicable to the damping of sound by turbulent scattering in the atmosphere. (Author).