Experimental And Numerical Investigation Of Coherent Structures In Turbulent Wake Flows

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Experimental and Numerical Investigation of Coherent Structures in Turbulent Wake Flows

Author : F. H. Champagne
Publisher :
ISBN 13 :
Total Pages : 19 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis Experimental and Numerical Investigation of Coherent Structures in Turbulent Wake Flows by : F. H. Champagne

Experimental and Numerical Investigation of Coherent Structures in Turbulent Wake Flows

Author : F. H. Champagne
Publisher :
ISBN 13 :
Total Pages : 70 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis Experimental and Numerical Investigation of Coherent Structures in Turbulent Wake Flows by : F. H. Champagne

Download or read book Experimental and Numerical Investigation of Coherent Structures in Turbulent Wake Flows written by F. H. Champagne and published by . This book was released on 1989 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large scale coherent structures have been observed in two-dimensional wakes behind bluff bodies as well as non-vortex shedding bodies. There is a strong indication that these large scale structures are related to the two-dimensional instability modes of the slowly diverging mean wake flow. The Orr-Sommerfeld equation admits two solution modes for the two-dimensional plane wake. These are the sinuous mode with antisymmetric streamwise fluctuations and the varicose mode with symmetric streamwise fluctuations. The wake response to controlled sinuous and varicose types of disturbance waves was investigated. Sinuous disturbances at several amplitudes and frequencies were introduced to the wake of a flat plate by oscillating a small trailing edge flap. The Strouhal numbers of the disturbance waves were specially chosen so that the downstream location of the neutral point was well within the range of measurements. The streamwise variation of the half width of the wake an the centerline deficit was dependent on the amplitude level and showed dramatic deviations, starting near the neutral point, at large forcing levels from the well known square root behavior of the unforced case. The measured coherent Reynolds stresses were observed to change sign in the neighborhood of the neutral point as predicted from linear stability theory. The extent of the validity of linear stability theory was investigated. The wake was also forced with a sinuous disturbance of lower Strouhal number that was amplified over the entire range of measurements. (edc).

Turbulence and Coherent Structures

Author : O. Métais
Publisher : Springer Science & Business Media
ISBN 13 : 9401579040
Total Pages : 612 pages
Book Rating : 4.4/5 (15 download)

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Book Synopsis Turbulence and Coherent Structures by : O. Métais

Download or read book Turbulence and Coherent Structures written by O. Métais and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Experimental & Numerical Investigation of Coherent Structures

Author : F. H. Champagne
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (227 download)

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Book Synopsis Experimental & Numerical Investigation of Coherent Structures by : F. H. Champagne

Download or read book Experimental & Numerical Investigation of Coherent Structures written by F. H. Champagne and published by . This book was released on 1986 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimentally, several significant tasks were accomplished during the first year of the grant period. The first involved completing the Reynolds stress measurements behind various wake generators and demonstrating that the previously observed variation in the spreading rate of the mean flow field could be confirmed by the Reynolds stress results. This provides convincing evidence for the lack of universality of the turbulent structure of two dimensional small deficit wakes. The model decomposition work, initiated to investigate possible cause for the lack of universality, was completed. Varicose disturbances were successfully generated using a two flap mechanism to investigate the significance of the varicose mode. The amplitude ratio of the two modes, sinuous and varicose, appear to approach an asymptotic value in the far wake. Finally, varicose effects were accounted for in the model decomposition work by solving the Orr Sommerfeld equation. The varicose mode appears to be more affected by viscosity than the sinuous mode. Numerical simulations based on the complete Navier Stokes equation are under development for a somewhat simpler flow geometry than the wake, namely the free shear layer. Considerable progress has been made toward the development of numerical methods that are applicable to such simulations. For simplicity, the temporal model is being used first. A computer program based on the spatial model is nearly finished. The results of the two models will be directly compared.

Les Investigation of Coherent Structures in Boundary Layers and Wakes. Volume II: Wake Around Square Cylinder

Author :
Publisher :
ISBN 13 :
Total Pages : 180 pages
Book Rating : 4.:/5 (946 download)

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Book Synopsis Les Investigation of Coherent Structures in Boundary Layers and Wakes. Volume II: Wake Around Square Cylinder by :

Download or read book Les Investigation of Coherent Structures in Boundary Layers and Wakes. Volume II: Wake Around Square Cylinder written by and published by . This book was released on 2002 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Purpose of the present investigation is to assess the feasibility of simulating and studying coherent structures in turbulent shear layers, malting use of Large Eddy Simulations (LES). Volume I of present report has described the general background, the main development and the results obtained for wall bounded turbulent flow, particularly the turbulent charnel flow at equilibrium. The present Volume II is devoted to the study of the flow around an obstacle, in particular a cylinder with square cross section and infinlte length in span- wise direction. This test case belongs to a completely different class of flow respect the one analyzed in Volume I, and it is a rather severe test case for the LES code. Most of the advanced features of the code were exploited, and different simulations were performed, to collect, whenever possible, sufficient data to draw conclusions and remarks. Differently from the case of channel flow, were the code has been extensively validated and analyzed in detail, down to the level of turbulent kinetic energy budget, the present flow constitutes a still active area of basic research. The higher complexity of the flow, the absence of a second direction of homogeneity, beside the span-wise direction, the existence of a dominant frequency in the flow, the necessity of employing upwinding discretization for advection terms and other numerical difficulties have led to such complexities of execution that only the very basic set of statistics (statistical moments of first and second order) were obtained. At the same time, limits and draw-backs for current LES code implementation have been outlined. Most of the efforts were devoted to reach a sufficient similarity in behavior between LES simulation and reference experimental data; this attempt has led to build grids not perfectly suited to analyze structures applying the criteria based on the gradient of velocity tensor introduced in Volume L.

Ordinantie vande Ertzhertoghen onse Souvereyne Princen oyt feyt vande munte

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (312 download)

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Book Synopsis Ordinantie vande Ertzhertoghen onse Souvereyne Princen oyt feyt vande munte by :

Download or read book Ordinantie vande Ertzhertoghen onse Souvereyne Princen oyt feyt vande munte written by and published by . This book was released on 1619 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Simulation-based Analyses of Turbulent Wakes

Author : Sheel Nidhan
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (137 download)

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Book Synopsis Simulation-based Analyses of Turbulent Wakes by : Sheel Nidhan

Download or read book Simulation-based Analyses of Turbulent Wakes written by Sheel Nidhan and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent wakes are pervasive in man-made and natural environments. In the ocean and the atmosphere, these wakes interact with the background ambient stratification to give rise to a myriad of interesting phenomena, e.g., multistage decay of mean and turbulence, long-lived coherent structures, and the appearance of internal gravity waves, to name a few. With the rise in supercomputing power, high-fidelity numerical simulations have become an increasingly feasible way to investigate the phenomenology of these wakes. As these simulations become commonplace in research, there is an increased focus on the use of data-driven techniques to uncover the rich dynamics from the obtained datasets. This dissertation is an examination of turbulent wakes using data-driven techniques and numerical simulations. In the first part, spectral proper orthogonal decomposition is used to investigate a turbulent disk wake database at Re = 5 x 104 and Fr = [infinity], 10, 2. We first study the evolution of the vortex shedding mode and double helix mode in the unstratified wake (Fr = [infinity]), building on and refining the previous experimental studies. Thereafter, the SPOD analysis of the stratified wakes is performed that uncovers two new results: (a) coherence originating at the body gets stronger and lives longer with progressively increasing stratification levels and (b) for Fr [greater than and approximately equal to] 2, vortex shedding is the dominant mechanism of internal gravity wave generation. In the second part of the work, large eddy simulations (LES) are used to investigate the flow past a prolate 6:1 spheroid. Firstly, high-resolution hybrid simulation is used to simulate the far wake of a 6:1 spheroid at 0-degree angle of attack and Re = 105, Fr = 2 and 10. The far wake is compared to the above-mentioned disk database. The spheroid wakes show differences in locations at which mean wake transitions take place. These differences are explained in light of energy budgets. Secondly, large eddy simulations of flow past a 6:1 spheroid at Re = 5000, Fr = [infinity], 6, 1.9, 1, and a moderate angle of attack [alpha] = 10[superscript circle] are carried out. Body forces, mean wake and vorticity dynamics, and flow spectra are analyzed in detail and presented in the dissertation.

Scientific and Technical Aerospace Reports

Author :
Publisher :
ISBN 13 :
Total Pages : 892 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Scientific and Technical Aerospace Reports by :

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Turbulent Flows

Author : G. Biswas
Publisher : Narosa Publishing House
ISBN 13 :
Total Pages : 476 pages
Book Rating : 4.3/5 (91 download)

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Book Synopsis Turbulent Flows by : G. Biswas

Download or read book Turbulent Flows written by G. Biswas and published by Narosa Publishing House. This book was released on 2002 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book allows readers to tackle the challenges of turbulent flow problems with confidence. It covers the fundamentals of turbulence, various modeling approaches, and experimental studies. The fundamentals section includes isotropic turbulence and anistropic turbulence, turbulent flow dynamics, free shear layers, turbulent boundary layers and plumes. The modeling section focuses on topics such as eddy viscosity models, standard K-E Models, Direct Numerical Stimulation, Large Eddy Simulation, and their applications. The measurement of turbulent fluctuations experiments in isothermal and stratified turbulent flows are explored in the experimental methods section. Special topics include modeling of near wall turbulent flows, compressible turbulent flows, and more.

Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries

Author : Noushin Amini
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (812 download)

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Book Synopsis Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries by : Noushin Amini

Download or read book Turbulent Flow Analysis and Coherent Structure Identification in Experimental Models with Complex Geometries written by Noushin Amini and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flows and coherent structures emerging within turbulent flow fields have been extensively studied for the past few decades and a wide variety of experimental and numerical techniques have been developed for measurement and analysis of turbulent flows. The complex nature of turbulence requires methods that can accurately estimate its highly chaotic spatial and temporal behavior. Some of the classical cases of turbulent flows with simpler geometries have been well characterized by means of the existing experimental techniques and numerical models. Nevertheless, since most turbulent fields are of complex geometries; there is an increasing interest in the study of turbulent flows through models with more complicated geometries. In this dissertation, characteristics of turbulent flows through two different facilities with complex geometries are studied applying two different experimental methods. The first study involves the investigation of turbulent impinging jets through a staggered array of rods with or without crossflow. Such flows are crucial in various engineering disciplines. This experiment aimed at modeling the coolant flow behavior and mixing phenomena within the lower plenum of a Very High Temperature Reactor (VHTR). Dynamic Particle Image Velocimetry (PIV) and Matched Index of Refraction (MIR) techniques were applied to acquire the turbulent velocity fields within the model. Some key flow features that may significantly enhance the flow mixing within the test section or actively affect some of the structural components were identified in the velocity fields. The evolution of coherent structures within the flow field is further investigated using a Snapshot Proper Orthogonal Decomposition (POD) technique. Furthermore, a comparative POD method is proposed and successfully implemented for identification of the smaller but highly influential coherent structures which may not be captured in the full-field POD analysis. The second experimental study portrays the coolant flow through the core of an annular pebble bed VHTR. The complex geometry of the core and the highly turbulent nature of the coolant flow passing through the gaps of fuel pebbles make this case quite challenging. In this experiment, a high frequency Hot Wire Anemometry (HWA) system is applied for velocity measurements and investigation of the bypass flow phenomena within the near wall gaps of the core. The velocity profiles within the gaps verify the presence of an area of increased velocity close to the outer reflector wall; however, the characteristics of the coolant flow profile is highly dependent on the gap geometry and to a less extent on the Reynolds number of the flow. The time histories of the velocity are further analyzed using a Power Spectra Density (PSD) technique to acquire information about the energy content and energy transfer between eddies of different sizes at each point within the gaps.

Eddy Structure Identification in Free Turbulent Shear Flows

Author : J.P. Bonnet
Publisher : Springer
ISBN 13 :
Total Pages : 544 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Eddy Structure Identification in Free Turbulent Shear Flows by : J.P. Bonnet

Download or read book Eddy Structure Identification in Free Turbulent Shear Flows written by J.P. Bonnet and published by Springer. This book was released on 1993-09-30 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Lecture Notes On Turbulence And Coherent Structures In Fluids, Plasmas And Nonlinear Media

Author : Horst Punzmann
Publisher : World Scientific
ISBN 13 : 981447844X
Total Pages : 397 pages
Book Rating : 4.8/5 (144 download)

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Book Synopsis Lecture Notes On Turbulence And Coherent Structures In Fluids, Plasmas And Nonlinear Media by : Horst Punzmann

Download or read book Lecture Notes On Turbulence And Coherent Structures In Fluids, Plasmas And Nonlinear Media written by Horst Punzmann and published by World Scientific. This book was released on 2006-11-29 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is based on the lectures delivered at the 19th Canberra International Physics Summer School held at the Australian National University in Canberra (Australia) in January 2006.The problem of turbulence and coherent structures is of key importance in many fields of science and engineering. It is an area which is vigorously researched across a diverse range of disciplines such as theoretical physics, oceanography, atmospheric science, magnetically confined plasma, nonlinear optics, etc. Modern studies in turbulence and coherent structures are based on a variety of theoretical concepts, numerical simulation techniques and experimental methods, which cannot be reviewed effectively by a single expert.The main goal of these lecture notes is to introduce state-of-the-art turbulence research in a variety of approaches (theoretical, numerical simulations and experiments) and applications (fluids, plasmas, geophysics, nonlinear optical media) by several experts. A smooth introduction is presented to readers who are not familiar with the field, while reviewing the most recent advances in the area. This collection of lectures will provide a useful review for both postgraduate students and researchers new to the advancements in this field, as well as specialists seeking to expand their knowledge across different areas of turbulence research.

Technical Reports Awareness Circular : TRAC.

Author :
Publisher :
ISBN 13 :
Total Pages : 766 pages
Book Rating : 4.E/5 ( download)

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Book Synopsis Technical Reports Awareness Circular : TRAC. by :

Download or read book Technical Reports Awareness Circular : TRAC. written by and published by . This book was released on 1987-07 with total page 766 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Eddy Structure Identification

Author : J.P. Bonnet
Publisher : Springer
ISBN 13 : 3709126762
Total Pages : 366 pages
Book Rating : 4.7/5 (91 download)

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Book Synopsis Eddy Structure Identification by : J.P. Bonnet

Download or read book Eddy Structure Identification written by J.P. Bonnet and published by Springer. This book was released on 2014-05-04 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a unique opportunity to present in a single volume information that is needed for both experimentalists, theoreticians and computationalists for the detection, analysis, prediction and control of eddy structures in turbulent shear flows. Major identification techniques of Eddy Structures in Turbulent Shear Flows are presented together with applications to vortex dynamics, turbulence management and flow control, for experimental and numerical applications with new prediction methods: Eduction Schemes, Proper Orthogonal Decomposition, Stochastic Estimation, Pattern Recognition Analysis, Wavelet Transform. Illustrations of the use of the different methods are given.

IUTAM Symposium on Simulation and Identification of Organized Structures in Flows

Author : J.N. Sørensen
Publisher : Springer Science & Business Media
ISBN 13 : 9401146012
Total Pages : 512 pages
Book Rating : 4.4/5 (11 download)

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Book Synopsis IUTAM Symposium on Simulation and Identification of Organized Structures in Flows by : J.N. Sørensen

Download or read book IUTAM Symposium on Simulation and Identification of Organized Structures in Flows written by J.N. Sørensen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains reviewed papers from the 1997 IUTAM Symposium, presenting the latest results from leading scientists within the field of detection and simulation of organized flow structures. It describes various aspects of complex, organized flow motion, including topics from decomposition techniques to topological concepts.

Experimental and Numerical Investigation of Developing Turbulent Flow Over a Wavy Wall

Author : Vinicius Martins Segunda
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)

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Book Synopsis Experimental and Numerical Investigation of Developing Turbulent Flow Over a Wavy Wall by : Vinicius Martins Segunda

Download or read book Experimental and Numerical Investigation of Developing Turbulent Flow Over a Wavy Wall written by Vinicius Martins Segunda and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flow over a wavy wall in a horizontal channel is investigated by experimental and numerical methods. The thorough problem understanding can advance turbulent flow physics knowledge for separating and reattaching flows. Another important consideration is the performance evaluation of mathematical models used in computational fluid dynamics (CFD) codes to predict the flow characteristics. This study explores numerical models because they are critically important to the design and performance evaluation of engineering systems. The experimental data are obtained to provide repository data and more insights into the flow physics considering both the flow development and fully periodic regions. A channel with a wavy bottom wall is considered for this study, and its main characteristic is a value of 10 for the ratio between the wave length and wave amplitude. A high-resolution particle image velocimetry (PIV) system is used to obtain detailed measurements of velocity at Reynolds number of 5040, 8400, 10700 and 13040 in both the developing and fully periodic regions. The numerical simulations are performed with a commercial CFD code using four eddy viscosity turbulence models and three Second-Moment Closure (SMC) turbulence models. This work assessed the predictive accuracy of a total of seven turbulence models. The experimental study covered a lack of data for the flow development within the waves, prior the periodic condition region, and it supported the turbulence models evaluation. The experiments provided features of the flow such as the recirculation regions, Reynolds stresses, and turbulent kinetic energy production at different channel locations. A comprehensive comparison between models and experimental data revealed a significant dependency on the turbulence model formulation and on the wall treatment selection for the flow development and fully periodic regions predictions.

Transition, Turbulence, and Noise

Author : Reda R. Mankbadi
Publisher : Springer Science & Business Media
ISBN 13 : 1461527449
Total Pages : 386 pages
Book Rating : 4.4/5 (615 download)

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Book Synopsis Transition, Turbulence, and Noise by : Reda R. Mankbadi

Download or read book Transition, Turbulence, and Noise written by Reda R. Mankbadi and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence takes place in most flow situations whethertheyoccur naturally or in technological systems. Therefore, considerable effort is being expended in an attempt to understand the phenomenon of turbulence. The recent discovery ofcoherent structure in turbulent shear flows and the modem developments in computer capabilities have revolutionized research work in turbulence. There is a strong evidence that the coherent structure in turbulent shear flows is reminiscent of nonlinear stability waves. As such, the interest in nonlinear stability waves has increased not only for the understandingofthe latterstages of the laminar-turbulent transition process, but also for understanding the coherent structures in turbulent flows. Also. the advances in computers have made direct numerical simulation possible at Low-Reynolds numbers and large-eddy simulation possible at high Reynolds numbers. This made first-principles prediction of turbulence-generated noise feasible. Therefore, this book aims at presenting a graduate-level introductory study of turbulence while accounting for such recent views of concern to researchers. This book is an outgrowth oflecture notes on the subject offered to graduate students in engineering. The book should be of interest to research engineers and graduatestudents in science and engineering. The theoretical basis presented is sufficient not only for studying the specialized literature on turbulence but also for theoretical investigations on the subject.