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 Mechanism of Noise Generation in the Turbulent Boundary Layer written by and published by . This book was released on 1964 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Noise Generation in Transonic Wind Tunnels written by M. O. Varner and published by . This book was released on 1975 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an attempt to determine the parameters characterizing the noise environment in transonic tunnels, noise-generating mechanisms for porous-wall tunnels with 60-deg inclined holes were isolated and studied. The noise environment in the test section is separated into three distinct parts: the noise due to jet flow through the porous walls, a wall hole-tunnel resonance phenomena, and the turbulent boundary layer on the test section walls and in the diffuser. Each part is analyzed separately for the effects of aerodynamic and geometric flow constraints on the frequency and power characteristics. The contribution of each of the acoustic models to the test section free-stream fluctuating pressure level is also examined.
Download or read book Computational Analysis of Noise Generation by a Rotor Ingesting Turbulent Boundary Layer on an Axisymmetric Body of Revolution written by Di Zhou and published by . This book was released on 2021 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 Boundary Layer Development and Flow induced Noise of Airfoils written by Laura Botero Bolívar and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Non equilibrium Wall bounded Turbulence and Associated Noise Generation written by Saurabh Pargal and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present study investigates the response of turbulence in a non-equilibrium flows such as transient periodic channel flows and spatially developing boundary layers subjected to pressure gradients. Such a fundamental study is important to understand noise generation in complex wall-bounded turbulent flows. First, to understand the flow dynamics in transient accelerating flows, direct numerical simulations (DNS) of periodic channel flows responding to an impulse acceleration are carried out. The turbulent flow undergoes reverse transition toward a quasi-laminar state, followed by a retransition phase to the new equilibrium state. To reduced simulation cost, the minimal-span methodology is applied and evaluated for simulations of transient flows.Next, to study non-equilibrium boundary layer flows in the presence of convex wall curvature, DNS simulations over an airfoil (suction side) and a flat plate are compared. Both cases are characterized by matching adverse pressure gradient (APG) along the streamwise direction. For the airfoil boundary layer, existing DNS data obtained by Wu et al. (2019) of flow around a controlled-diffusion (CD) airfoil is used. For the flat-plate boundary layer, a DNS simulation is carried out, with prescribed pressure gradient distribution that matches that of the airfoil case. Comparison between the two cases shows how wall curvature affects turbulence in an APG boundary layer. Overall, similar boundary layer development in both cases indicates that a flat-plate boundary layer can serve as a low-cost surrogate of an airfoil boundary layer.Lastly, various existing analytical models are evaluated on their predictions of wall pressure fluctuations, which are essential for fan noise prediction. Limitations of the existing models are evaluated; new parameters that do not involve the ill-defined wall friction in a boundary layer under strong APG are proposed. The primary role of the mean velocity logarithmic layer in affecting the overlap range of the wall pressure spectrum is also demonstrated. A new wall pressure spectrum model is proposed and tested in a wide range of boundary layer flow scenarios. The new wall pressure spectrum model is the first generalized model designed for boundary layer flows with a wide range of pressure gradients and Reynolds numbers.
Download or read book Wall pressure Fluctuations and Pressure velocity Correlation in Turbulent Boundary Layers written by John S. Serafini and published by . This book was released on 1963 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Note written by and published by . This book was released on 1975 with total page 826 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeroacoustics of Turbulent Mixing Layers written by Arjun Sharma and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet noise is an important contributor to overall aircraft noise. The flow near the jet nozzle is a spatially developing mixing layer and influences flow dynamics further downstream. The present study focuses on the influence of inflow conditions on mixing layer development and noise generation mechanisms using large-eddy simulations. Large-eddy simulations of spatially developing, turbulent mixing layers with splitter plate included in the computational domain are presented. Different inflow condition cases with initially laminar boundary layers (abbreviated as LBL) and turbulent boundary layers (abbreviated as TBL) are considered. Effect of heating, keeping the velocity ratio fixed, is analyzed for both. For each case, the mean and turbulent intensity profiles collapse when plotted in similarity coordinates. The development distance to achieve self-similarity in the mean velocity profile is found to be shortest for cases with turbulent exit boundary layers. The growth rate of the shear layer and peak self-similar values of the turbulent intensities are found to be in agreement with available experiments. It is observed that with heating, the initial instability is accelerated but the saturation self-similar amplitude of Reynolds stress components do not vary. The saturation amplitudes of density fluctuations were found to increase proportionally to difference in free-stream densities whereas near-field pressure fluctuations were found to decrease with heating. A simple scaling is suggested for the near-field pressure fluctuation amplitude. The observed scaling laws were also confirmed by simulation data from two-dimensional direct numerical simulations. For LBL, sound radiation is observed in downstream direction peaked roughly at 30 degrees. The vortex pairing and breakdown to turbulence contribute significantly to the radiated sound. For TBL, the acoustic field near the shear layer is significantly weaker and noise due to passage of boundary layer eddies over the trailing edge is observed. For both the cases, a reduction in overall sound pressure levels in the far-field is observed with heating. Analysis of relative importance of Reynolds stress autocorrelation tensor components is presented to explain the effects of heating.
Download or read book Technical Abstract Bulletin written by and published by . This book was released on 1967 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Generation in Transonic Wind Tunnels written by and published by . This book was released on 1975 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an attempt to determine the parameters characterizing the noise environment in transonic tunnels, noise-generating mechanisms for porous-wall tunnels with 60-deg inclined holes were isolated and studied. The noise environment in the test section is separated into three distinct parts: the noise due to jet flow through the porous walls, a wall hole-tunnel resonance phenomena, and the turbulent boundary layer on the test section walls and in the diffuser. Each part is analyzed separately for the effects of aerodynamic and geometric flow constraints on the frequency and power characteristics. The contribution of each of the acoustic models to the test section free-stream fluctuating pressure level is also examined.
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:
