Download or read book An Interaction Noise Between Vortex and Airfoil written by Jinzhang Feng and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Mechanisms of Transonic Vortex Airfoil Interaction written by H.-M. Lent and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Generation and Boundary Layer Effects in Vortex Airfoil Interaction and Methods of Digital Hologram Analysis for These Flow Fields written by G. E. Meier and published by . This book was released on 1987 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanism of sound generation and the kind of viscid interaction of vortices with airfoils in an airflow is investigated. Experiments have been performed in regular, quasi-stationary flow with vortices of a Karman vortex street. Depending on the dimensions of vortices and airfoils, their distance, and the flow Machnumbers, different kinds of upstream propagating sound waves occur. Keywords: Noise, Boundary layer, Vortex airfoil interaction, Secondary vortex, Vortex noise, Digital interferogram analysis, Fringe evaluation, Image processing.
Download or read book Theory of Sound Production by Vortex Airfoil Interaction written by M. S. Howe and published by . This book was released on 1988 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analysis is made of the sound produced when a field of vorticity is cut by an airfoil in low Mach number flow. A general formula is given for the acoustic pressure when the airfoil is rigid and the chord is acoustically compact. This expresses the radiation in terms of an integral over the region occupied by the vorticity; the integrand contains factors describing the influence of the thickness, twist and camber of the airfoil. Explicit analytical results are derived for the case of a rectilinear vortex, having small core diameter and finite axial velocity defect, which is 'chopped' by an airfoil of large aspect ratio. The acoustic signature generally comprises two components associated respectively with the axial and azimuthal vorticity, the latter being determined by the velocity defect distribution within the core. Sound is generated predominantly when the core is in the neighborhoods of the leading and trailing edges. The contribution from the trailing edge is usually small, however, because of destructive interference between sound produced by edge-diffraction of near field energy of the vortex and that produced by vorticity shed into the wake of the airfoil in order to satisfy the unsteady Kutta condition that the pressure and velocity should be bounded at the edge.
Download or read book Airfoil Self Noise and Prediction written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given. Brooks, Thomas F. and Pope, D. Stuart and Marcolini, Michael A. Langley Research Center AEROACOUSTICS; AERODYNAMIC NOISE; AIRFOIL PROFILES; AIRFOILS; BLADE-VORTEX INTERACTION; BOUNDARY LAYER SEPARATION; BOUNDARY LAYERS; NOISE PREDICTION (AIRCRAFT); VORTEX SHEDDING; AERODYNAMIC STALLING; APPLICATIONS PROGRAMS (COMPUTERS); NOISE MEASUREMENT; NOISE SPECTRA; ROTARY WINGS; STROUHAL NUMBER; TRAILING EDGES; VORTICES; WIND TUNNEL TESTS...
Download or read book Aerodynamic Sound Generation Due to Vortex aerofoil Interaction Part 2 Analysis of the Acoustic Field written by and published by . This book was released on 1972 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Parametric Study of Transonic Blade Vortex Interaction Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several parameters of transonic blade-vortex interactions (BVI) are being studied and some ideas for noise reduction are introduced and tested using numerical simulation. The model used is the two-dimensional high frequency transonic small disturbance equation with regions of distributed vorticity (VTRAN2 code). The far-field noise signals are obtained by using the Kirchhoff method with extends the numerical 2-D near-field aerodynamic results to the linear acoustic 3-D far-field. The BVI noise mechanisms are explained and the effects of vortex type and strength, and angle of attack are studied. Particularly, airfoil shape modifications which lead to noise reduction are investigated. The results presented are expected to be helpful for better understanding of the nature of the BVI noise and better blade design. Lyrintzis, A. S. Unspecified Center...
Download or read book Sound Flow Interactions written by Y. Auregan and published by Springer. This book was released on 2007-06-18 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: The coupling between acoustic waves and fluid flow motion is basically nonlinear, with the result that flow and sound modify themselves reciprocally with respect to generation and propagation properties. As a result this problem is investigated by many different communities, such as applied mathematics, acoustics and fluid mechanics. This book is the result of an international school which was held to discuss the foundation of sound--flow interactions, to share expertise and methodologies, and to promote cross-fertilization between the different disciplines involved. It consists essentially of a set of pedagogical lectures and is meant to serve not only as a compact source of reference for the experienced researcher but also as an advanced textbook for postgraduate students, and nonspecialists wishing to familiarize themselves in depth, at a research level, with this fascinating subject.
Download or read book Modelling of Airfoil vortex Interaction and Aplication to a Helicopter Rotor written by Gilles Rahier and published by . This book was released on 1998 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelling of Airfoil vortex Interaction and Application to a Helicopter Rotor written by Gilles Rahier and published by . This book was released on 1998 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Body Interaction and Sound Generation in Low Speed Flow written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-15 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of sound generation by vortices interacting with an arbitrary body in a low-speed flow has been investigated by the method of matched asymptotic expansions. For the purpose of this report, it is convenient to divide the problem into three parts. In the first part the mechanism of the vortex/body interaction, which is essentially the inner solution in the inner region, is examined. The trajectories for a system of vortices rotating about their centroid are found to undergo enormous changes after interaction; from this, some interesting properties emerged. In the second part, the problem is formulated, the outer solution is found, matching is implemented, and solutions for acoustic pressure are obtained. In the third part, Fourier integrals are evaluated and predicated results presented. An examination of these results reveals the following: (a) the background noise can be either augmented or attenuated by a body after interaction, (b) sound generated by vortex/body interaction obeys a scaling factor, (C) sound intensity can be reduced substantially by positioning the vortex system in the "favorable" side of the body instead of the "unfavorable" side, and (d) acoustic radiation from vortex/bluff-body interaction is less than that from vortex/airfoil interaction under most circumstances. Kao, Hsiao C. Glenn Research Center RTOP 522-31-23...
Download or read book Vortex Body Interaction and Sound Generation in Low Speed Flow written by Hsiao C. Kao and published by . This book was released on 1998 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory of Vortex Sound written by M. S. Howe and published by Cambridge University Press. This book was released on 2003 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Table of contents
Download or read book Vortex Airfoil Interaction and Application of Methods for Digital Fringe Analysis written by G. E. Meier and published by . This book was released on 1986 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: The interaction of convected vortices with different airfoils was investigated in a transonic duct and a shock tube flow. Different kinks of separation and secondary vortex generation have a governing influence on airfoil-vortex interaction. Steep sound waves propagating upstream are generated at the leading edge. A system for digital processing of flow interferograms has been developed.
Download or read book Wake Body Interaction Noise Simulated by the Coupling Method Using CFD and BEM written by Masaaki Mori and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many engineering applications, obstacles often appear in the wake of obstacles. Vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. This phenomenon is called wake-body interaction or body-vortex interaction (BVI). The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this chapter, we review the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results show that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increase in the spacing between the two obstacles.
Download or read book Acoustics and Aerodynamic Sound written by Michael Howe and published by Cambridge University Press. This book was released on 2015 with total page 311 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an introductory account of the theory of sound production and propagation and its interactions with solid structures. It includes general theory, diffraction and scattering theory, aerodynamic sound and fluid-structure-acoustic interactions, and a chapter of worked examples. It is intended for a one-semester course on acoustics at the advanced undergraduate or graduate level.
Download or read book Vortex Dynamics Theories and Applications written by Zambri Harun and published by BoD – Books on Demand. This book was released on 2020-12-09 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book comprises of different areas in which vortex dynamics is important, its generation, evolution, interactions with other motions, and finally the ways it can be controlled. Vortex characteristics are important in many aspects of our lives, from blood circulation in the arteries to the high-speed jet. Flow control and manipulation of vortices have been used to reduce drag for large tankers resulting in billions of dollars in savings. An effective smoke management system must be put in place for critical areas to ensure the safety of people, for example in a very large shopping complex or a large airport. Advanced computational and cloud-computing facilities have contributed significantly to large-scale simulation projects. Therefore, validations could be performed for larger windows of study so that it can now cover the entire e.g. central business district (CBD) for urban heat island (UHI) study or land-ocean interactions.
