Large Scale Structures in Free Turbulent Shear Flows PDF Download
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Author: J. P. Bonnet
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: J. P. Bonnet
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: J. T. C. Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 14
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Book Description
The existence of organized structures in turbulent shear flow has been the subject of recent observational discoveries in both the laboratory and in the atmosphere and ocean. The resent work on modeling such structures in a temporally developing, horizontally homogeneous turbulent free shear layer has been extended to the spatially developing mixing layer, there being no available rational transformation between the two nonlinear problems. The basis for the consideration is the kinetic energy development of the mean flow, large-scale structure and fine-grained turbulence with a conditional average, supplementing the usual time average, to separate the nonrandom from the random part of the fluctuations. The integrated form of the energy equations and the accompanying shape assumptions, is used to derive amplitude equations for the mean flow, characterized by the shear layer thickness, the nonrandom and random components of flow which are characterized by their respective energy densities. In general, the large-scale structure augments the spreading of the shear layer and enhances the fine-grained turbulence by taking energy from the mean flow and transferring it to the turbulence as it amplifies and subsequently decays. The maximal amplitude of the large-scale structure is attained by the initially most amplified mode, however, the relative enhancement of the fine-grained turbulence is achieved by both the magnitude of the large-scale structure and its streamwise lifetime. Thus a greater enhancement of the turbulence is achievable by the lower frequency mdoes which have longer streamwise lifetimes. The large-scale structure can also be controlled by increasing the initial level of turbulence, which would render its decay more rapidly. (Author).
Author: J.P. Bonnet
Publisher: Springer Science & Business Media
ISBN: 9401120986
Category : Technology & Engineering
Languages : en
Pages : 504
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Book Description
The existence and crucial role played by large-scale, organized motions in turbulent flows are now recognized by industrial, applied and fundamental researchers alike. It has become increasingly evident that coherent structures influence mixing, noise, vibration, heat transfer, drag, etc... The accelera tion of the development of both experimental and computational programs devoted to this topic has been evident at several recent international meet ings. One of the first questions which experimentalists or numerical analysts are faced with is: how can these structures be separated from the background turbulence? This is a nontrivial task because the coherent structures are gen erally embedded in a random field and the technique used to determine when and where certain structures are passing, or their averaged characteristics (in the more probable or dominant role sense) is directly related to the definition of the coherent structure. Several methods or approaches are available and the choice of a particular one is generally dependent on the desired informa tion. This choice depends not only on the definition of the structure, but also on the experimental and numerical capabilities available to the researcher.
Author: Franz Durst
Publisher: Springer Science & Business Media
ISBN: 3642714358
Category : Science
Languages : en
Pages : 367
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Book Description
The first four symposia in the series on turbulent shear flows have been held alternately in the United States and Europe with the first and third being held at universities in eastern and western States, respectively. Continuing this pattern, the Fifth Symposium on Turbulent Shear Flows was held at Cornell University, Ithaca, New York, in August 1985. The meeting brought together more than 250 participants from around the world to present the results of new research on turbulent shear flows. It also provided a forum for lively discussions on the implications (practical or academic) of some of the papers. Nearly 100 formal papers and about 20 shorter communications in open forums were presented. In all the areas covered, the meeting helped to underline the vitality of current research into turbulent shear flows whether in experimental, theoretical or numerical studies. The present volume contains 25 of the original symposium presentations. All have been further reviewed and edited and several have been considerably extended since their first presentation. The editors believe that the selection provides papers of archival value that, at the same time, give a representative statement of current research in the four areas covered by this book: - Homogeneous and Simple Flows - Free Flows - Wall Flows - Reacting Flows Each of these sections begins with an introductory article by a distinguished worker in the field.
Author: O. Métais
Publisher: Springer Science & Business Media
ISBN: 9401579040
Category : Technology & Engineering
Languages : en
Pages : 612
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Book Description
In the last 25 years, one of the most striking advances in Fluid Mecha nics was certainly the discovery of coherent structures in turbulence: lab oratory experiments and numerical simulations have shown that most turbulent flows exhibit both spatially-organized large-scale structures and disorganized motions, generally at smaller scales. The develop ment of new measurement and visualization techniques have allowed a more precise characterization and investigation of these structures in the laboratory. Thanks to the unprecedented increase of computer power and to the development of efficient interactive three-dimensional colour graphics, computational fluid dynamicists can explore the still myste rious world of turbulence. However, many problems remain unsolved concerning the origin of these structures, their dynamics, and their in teraction with the disorganized motions. In this book will be found the latest results of experimentalists, theoreticians and numerical modellers interested in these topics. These coherent structures may appear on airplane wings or slender bodies, mixing layers, jets, wakes or boundary-layers. In free-shear flows and in boundary layers, the results presented here highlight the intense three-dimensional character of the vortices. The two-dimensional large scale eddies are very sensitive to three-dimensional perturbations, whose amplification leads to the formation of three-dimensional coherent vorti cal structures, such as streamwise, hairpin or horseshoe vortex filaments. This book focuses on modern aspects of turbulence study. Relations between turbulence theory and optimal control theory in mathematics are discussed. This may have important applications with regard to, e. g. , numerical weather forecasting.
Author: M. A. Badri Narayanan
Publisher:
ISBN:
Category :
Languages : en
Pages : 21
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Book Description
The basic understanding of the physics of turbulence has undergone many radical changes in the last few years. Turbulent fluctuations which were considered to be purely random in nature is no more accepted to behave in that fashion but made up of somewhat coherent and orderly structures mixed with noise like random disturbances. The major difficulty experienced in the experimental investigations is the identification of these coherent structures from the overall signal. New methods are being developed to identify them. These orderly motions are large in scale and seem to play an important role in the dynamics of the mixing and the transport processes which are the essential features of turbulence. In this paper the properties of the large scale fluctuations in boundary layers as well as in shear flows are discussed. (Author).
Author: Albert Alan Townsend
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 338
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Author: Javier Jiménez
Publisher: Springer Science & Business Media
ISBN: 1461537509
Category : Science
Languages : en
Pages : 359
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Book Description
The aim of this Advanced Research Workshop was to bring together Physicists, Applied Mathematicians and Fluid Dynamicists, including very specially experimentalists, to review the available knowledge on the global structural aspects of turbulent flows, with an especial emphasis on open systems, and to try to reach a consensus on their possible relationship to recent advances in the understanding of the behaviour of low dimensional dynamical systems and amplitude equations. A lot has been learned during recent years on the non-equilibrium behaviour of low dimen sional dynamical systems, including some fluid flows (Rayleigh-Benard, Taylor-Couette, etc. ). These are mostly closed flows and many of the global structural features of the low dimensional systems have been observed in them, including chaotic behaviour, period doubling, intermit tency, etc. . It has also been shown that some of these flows are intrinsically low dimensional, which accounts for much of the observed similarities. Open flows seem to be different, and experimental observations point to an intrinsic high dimensionality. However, some of the tran sitional features of the low dimensional systems have been observed in them, specially in the intermittent behaviour of subcritical flows (pipes, channels, boundary layers with suction, etc. ), and in the large scale geometry of coherent structures of free shear flows (mixing layers, jets and wakes).
Author: Franz Durst
Publisher: Springer Science & Business Media
ISBN: 3642788238
Category : Science
Languages : en
Pages : 465
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Book Description
The inaugural Symposium on Turbulent Shear Flows was held at The Pennsylvania State University in 1977. Thereafter the locations for the biennial symposium have alternated between the USA and Europe. However, the ninth Symposium on Turbu lent Shear Flows was awarded to Japan in recognition of the strong support researchers of the Pacific Rim countries have given previous symposia. The University of Kyoto was the host institution and the meeting was held in the Inter national Conference Hall. The Local Arrangements Committee did a superb job scheduling traditional Japanese dinners and arranging visits to the many cultural treasures in the Kyoto region. The meeting attracted more than 260 offers of papers. Thirty-three sessions were scheduled to accommodate the 138 papers accepted for oral presentation. In addition a poster session was scheduled on each of the three days to accommodate a total of 42 poster presentations. From the presentations at the symposium 24 have been selected for inclusion in this volume. The authors of these papers have revised them taking into consideration comments made during their oral presentation and recommendations made by the Editors. Four subject areas are identified, namely closures and fundamentals, free flows, wall flows, and combustion and recirculating flows. Eminent authorities have prepared introductory articles fot each topic to put the individual contributions in context with each other and with related research.
