Download or read book Pulsed Sound Measurements of the Influence of High Amplitude Noise on Boundary Layer Transition to Turbulence written by and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of leading-edge receptivity to high-amplitude acoustic forcing was conducted in the low- turbulence Arizona State University Unsteady Wind Tunnel. The experiment examined unstable wave evolution in a Blasius boundary layer produced on a flat plate. A pulsed-sound technique was employed to generate Measurements of receptivity coefficients for a 20:1 modified-super-ellipse leading edge. The leading-edge profile ensures that there is no curvature discontinuity at the flat-plate juncture, therefore limiting the receptivity sources. The goal of the pulsed-sound method was to prevent the superposition of the Stokes and Tollmien-Schlichting (T-S) waves that were prevalent in previous experiments. Separation was achieved via a short acoustic pulse, followed by the conditional sampling of the boundary layer. The resulting signal yielded a pure T-S wave. The signals were examined in the frequency domain, where the magnitudes of the ensemble-averaged Fourier coefficients were used to calculate the receptivity coefficients. These experiments resolved the erroneous narrow pass-band response of all other experiments, extended the measurement range of previous experiments, and provided very good validation of analytical and numerical models. Results revealed good agreement with linear stability theory. Receptivity coefficients are presented and the first step to a transition prediction scheme has been completed.
Download or read book Influence of High Amplitude Noise on Boundary Layer Transition to Turbulence written by William Saric and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work completes a series of detailed experiments of boundary layers undergoing transition to turbulence with the major effort directed toward the most important issue facing the understanding of fundamental causes of transition, i.e., the receptivity to freestream disturbances. This problem is reviewed in detail by Saric et al. (1994). The present effort concentrates on leading-edge receptivity and receptivity of two-dimensional roughness. The effects of large-amplitude freestream noise is considered with the effort directed toward determining the limits of linear receptivity. Single-frequency and broad-band sound waves are used along with 2-D roughness elements to determine how the unstable waves are initiated. New data are presented on leading edge-receptivity that clarify some difficulties with previous experimental work. Comparisons with recent DNS are excellent. Data are also presented for nonlinear receptivity of 2-D roughness elements. It is shown that there is little difference between the single-frequency excitation and white noise in that the response is still keenly triggered by the amplitude of the individual mode. Thus a single frequency at 120 dB is more dangerous than white noise at 120 dB where the energy is distributed of many modes.
Download or read book Vibration and Near field Sound of Thin walled Cylinders Caused by Internal Turbulent Flow written by Paul F. R. Weyers and published by . This book was released on 1960 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Noise Modeling Measurement and Control written by and published by . This book was released on 1991 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Sources in Turbulent Shear Flows Fundamentals and Applications written by Roberto Camussi and published by Springer Science & Business Media. This book was released on 2013-02-11 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Mechanism of Noise Generation in the Turbulent Boundary Layer written by John Laufer and published by . This book was released on 1964 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first chapter briefly states the problem and gives its historical development; the second reviews some basic notions of classical acoustics with special emphasis on the sound field produced by elementary sound sources, while the third one contains the generalized wave equation governing the pressure field radiated by nonuniform nonstationary flow. Subsequent chapters describe the methods proposed by the various authors for finding a solution to the radiation problem. The experimental approach is discussed. (Author).
Download or read book Effect of Turbulent Boundary Layer Flow on Measurement of Acoustic Pressure and Intensity Revised written by G. C. Lauchle and published by . This book was released on 1984 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic measurements performed with pressure sensors (microphones and hydrophones) can be subject to misinterpretation if the sensors are in contact with a turbulent boundary layer flow. This misinterpretation is a result of non-propagating pressure fields (flow noise) generated by the turbulent motions of the fluid. In this paper, a simple analysis is given whereby the flow noise response of a pressure sensor placed in a turbulent boundary layer flow can be estimated. If the purpose of the sensor is to measure the sound emitted from an independent source outside of the turbulent boundary layer, then a bias for the measurement can be calculated. A bias formula for intensity measurements made with two-sensors under a turbulent boundary layer is also derived under the assumption of a very low Mach number flow. (Author).
Download or read book An experimental investigation of turbulence excited panel vibration und noise boundary layer noise written by M. Y. El Baroudi and published by . This book was released on 1963 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Uncorrelated Noise in Turbulence Measurements written by D. H. Lenschow and published by . This book was released on 1985 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Applications of measurements. Theoretical considerations. Numerical noise simulation. Measurement of aerosols. Effects on spectra and structure functions.
Download or read book Noise from Interaction of Flow with Rigid Surfaces written by Richard E. Hayden and published by . This book was released on 1972 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: A brief review of some fundamental aspects of sound arising from turbulent boundary layers, noise due to flow past a single discontinuity (trailing edge), noise from airfoils operating in turbulent flow, and noise due to rigid flow discontinuities (spoilers) immersed in rigid ducts is presented. Emphasis is on dipole-like sound fields associated with turbulent flow past a trailing edge, rigid bodies in turbulence and in-duct spoilers. Representative available data are reviewed and evaluated in terms of theoretical considerations and, where possible, empirical prediction techniques are given in terms of convenient aerodynamic and geometric parameters. Limitations on current knowledge are discussed.
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).
Download or read book Flow Noise written by Con Doolan and published by Springer Nature. This book was released on 2022-05-10 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the importance of sound produced by fluid flow or flow-induced noise. Noise created by unsteady flow creates high levels of environmental noise pollution, a known public health problem, and can compromise the acoustic qualities of marine vessels. There is a seemingly ever-growing list of modern technology that created flow-induced noise which includes aircraft, wind turbines, submarines, drones, high-speed rail, and cooling fans. More scientists and engineers are required to incorporate the effects of flow-induced noise in their work. This book also provides a comprehensive introduction to the theory underpinning the understanding of flow-induced noise.
Download or read book Noise Due to the Interaction of Boundary Layer Turbulence with a Marine Propulsor Or an Aircraft Compressor written by Neil Moiseev and published by . This book was released on 1976 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The sound generated by the interaction of inlet boundary layer turbulence with a rotating blade row is investigated. To experimentally study this radiated sound, an existing aeroacoustic facility was modified to produce the inflows desired. The rotor was operated in air with different blade space-to-chord ratios, different flow coefficients and different anisotropic, nonhomogeneous turbulent inflows. The inflows ingested are: (1) natural boundary layer on hub and annulus wall, (2) a tripped boundary layer on the hub, and (3) a fully developed boundary layer on the hub. The turbulence intensities and length scales were altered by placing a grid at the inlet. The sound pressure level is found to be directly proportional to the turbulence intensity squared and inversely proportional to the ratio of axial length scale to blade spacing.
Download or read book An Experimental Investigation of Turbulence excited Panel Vibration and Noise boundary layer Noise written by M. Y. El Baroudi and published by . This book was released on 1963 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book More on Noise Produced by Boundary layer Turbulence written by Alan Powell and published by . This book was released on 1963 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt: The question of possible sound produced by stresses at a rigid surface is again discussed. It has been previously pointed out that these stresses are effective sources, being the reac tion to momentum fluctuations in a contiguous flow and with which the true sound sources are to be associated. There is no error in the orig inal general formalism, and no confusion need exist between hydrodynamic pressure and sound field pressure in the limits of very small sur faces (when net forces are to directly associated with dipole radiation) and of very large plane surfaces (when the surface pressures merely rep resent reflections of the quadrupole flow noise). (Author).
Download or read book Entwurf eines Criminal Gesetzbuches f r den Canton Basel written by and published by . This book was released on 1819 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sound Radiation from a Turbulent Boundary Layer written by John Laufer and published by . This book was released on 1961 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
