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Author: Sarah Moussa Hussein
Publisher:
ISBN:
Category : Numerical analysis
Languages : en
Pages : 192
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Book Description
Turbulence has been a topic of scientific research for years. Characterized by unorganized chaotic motion and irregular fluctuations, it persists as one of the most challenging topics in fluid mechanics despite volumes of documented research and crucial findings. This begs the question: What is turbulence and why is it so challenging? Turbulence research studies cover a wide spectrum of branches from fundamental flow propagation to different turbulence interactions. This research project investigates the simplest class of turbulent flow studies, homogeneous isotropic turbulence. In a quest to advance the fundamental understanding of turbulence physics, a direct numerical simulation tool is developed. The tool generates a turbulent periodic cube with vortical fluctuations and three interaction case studies. The evolution of the velocity in time is derived from the Navier-Stokes equations. These governing equations are integrated, along with initial and boundary conditions, to formulate turbulence. Fully-developed turbulence is achieved when the Tavoularis (1978) criterion of axial velocity variation is met. Output data sets are collected for numerical analysis. The turbulence periodic cube geometry is assessed for its applicability in this study. The simplified structure is found to be efficient and facilitated. The interaction case studies of shock-turbulence and detonation-turbulence are compared to an unforced flow interaction. The case studies are statistically analyzed and visualized yielding important conclusions on the effects of the fluctuations, heat release, detonation inherent length scale, and detonation intrinsic instability on the flow behavior. A mutual interaction is found between the turbulence structures and the strong detonation wave. An extension of the long-standing Tavoularis velocity skewness factor is suggested. The proposed velocity skewness vector quantifies the variation of the three velocity components in the three Cartesian coordinates. This comprehensive expression highlights the contribution of the three-dimensional velocity fluctuations to the turbulence state.
Author: Sarah Moussa Hussein
Publisher:
ISBN:
Category : Numerical analysis
Languages : en
Pages : 192
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Book Description
Turbulence has been a topic of scientific research for years. Characterized by unorganized chaotic motion and irregular fluctuations, it persists as one of the most challenging topics in fluid mechanics despite volumes of documented research and crucial findings. This begs the question: What is turbulence and why is it so challenging? Turbulence research studies cover a wide spectrum of branches from fundamental flow propagation to different turbulence interactions. This research project investigates the simplest class of turbulent flow studies, homogeneous isotropic turbulence. In a quest to advance the fundamental understanding of turbulence physics, a direct numerical simulation tool is developed. The tool generates a turbulent periodic cube with vortical fluctuations and three interaction case studies. The evolution of the velocity in time is derived from the Navier-Stokes equations. These governing equations are integrated, along with initial and boundary conditions, to formulate turbulence. Fully-developed turbulence is achieved when the Tavoularis (1978) criterion of axial velocity variation is met. Output data sets are collected for numerical analysis. The turbulence periodic cube geometry is assessed for its applicability in this study. The simplified structure is found to be efficient and facilitated. The interaction case studies of shock-turbulence and detonation-turbulence are compared to an unforced flow interaction. The case studies are statistically analyzed and visualized yielding important conclusions on the effects of the fluctuations, heat release, detonation inherent length scale, and detonation intrinsic instability on the flow behavior. A mutual interaction is found between the turbulence structures and the strong detonation wave. An extension of the long-standing Tavoularis velocity skewness factor is suggested. The proposed velocity skewness vector quantifies the variation of the three velocity components in the three Cartesian coordinates. This comprehensive expression highlights the contribution of the three-dimensional velocity fluctuations to the turbulence state.
Author: NA Schumann
Publisher: Springer Science & Business Media
ISBN: 3663001970
Category : Technology & Engineering
Languages : en
Pages : 350
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Book Description
This volume contains papers presented to a EUROMECH-Colloquium held in Munich, September 30 to October 2, 1985. The Colloquium is number 199 in a series of colloquia inaugurated by the European Mechanics Committee. The meeting was jointly organized by the 'Lehrstuhl fur Stromungsmechanik' at the 'Technische Universitat Munchen' and the 'Institut fur Physik der Atmosphare' of the 'Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt' (DFVLR) in Oberpfaffenhofen. 'Direct' and 'large eddy simulation' are terms which denote two closely con nected methods of turbulence research. In a 'direct simulation' (DS), turbu lent motion is simulated by numerically integrating the Navier-Stokes equations in three-dimensional space and as a function of time. Besides ini tial and boundary conditions no physical simplifications are involved. Com puter resources limit the resolution in time and space, though simulations with an order of one million discrete points in space are feasible. The simu lated flow fields can be considered as true realizations of turbulent flow fields and analysed to answer questions on the basic behaviour of turbulence. Direct simulations are valid as long as all the excited scales remain within the band of resolved scales. This means that viscosity must be strong enough to damp out the not resolved scales or the simulation is restricted to a lim ited integration-time interval only. In summary, DS provides a tool to investigate turbulent motions from first principles at least for a finite band of scales.
Author: Christophe Bailly
Publisher: Springer
ISBN: 3319161601
Category : Technology & Engineering
Languages : en
Pages : 375
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Book Description
This book covers the major problems of turbulence and turbulent processes, including physical phenomena, their modeling and their simulation. After a general introduction in Chapter 1 illustrating many aspects dealing with turbulent flows, averaged equations and kinetic energy budgets are provided in Chapter 2. The concept of turbulent viscosity as a closure of the Reynolds stress is also introduced. Wall-bounded flows are presented in Chapter 3 and aspects specific to boundary layers and channel or pipe flows are also pointed out. Free shear flows, namely free jets and wakes, are considered in Chapter 4. Chapter 5 deals with vortex dynamics. Homogeneous turbulence, isotropy and dynamics of isotropic turbulence are presented in Chapters 6 and 7. Turbulence is then described both in the physical space and in the wave number space. Time dependent numerical simulations are presented in Chapter 8, where an introduction to large eddy simulation is offered. The last three chapters of the book summarize remarkable digital techniques current and experimental. Many results are presented in a practical way, based on both experiments and numerical simulations. The book is written for a advanced engineering students as well as postgraduate engineers and researchers. For students, it contains the essential results as well as details and demonstrations whose oral transmission is often tedious. At a more advanced level, the text provides numerous references which allow readers to find quickly further study regarding their work and to acquire a deeper knowledge on topics of interest.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781719500807
Category :
Languages : en
Pages : 72
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Book Description
Numerical simulations of decaying homogeneous isotropic turbulence are performed with both low-order and high-order spatial discretization schemes. The turbulent Mach and Reynolds numbers for the simulations are 0.2 and 250, respectively. For the low-order schemes we use either second-order central or third-order upwind biased differencing. For higher order approximations we apply weighted essentially non-oscillatory (WENO) schemes, both with linear and nonlinear weights. There are two objectives in this preliminary effort to investigate possible schemes for large eddy simulation (LES). One is to explore the capability of a widely used low-order computational fluid dynamics (CFD) code to perform LES computations. The other is to determine the effect of higher order accuracy (fifth, seventh, and ninth order) achieved with high-order upwind biased WENO-based schemes. Turbulence statistics, such as kinetic energy, dissipation, and skewness, along with the energy spectra from simulations of the decaying turbulence problem are used to assess and compare the various numerical schemes. In addition, results from the best performing schemes are compared with those from a spectral scheme. The effects of grid density, ranging from 32 cubed to 192 cubed, on the computations are also examined. The fifth-order WENO-based scheme is found to be too dissipative, especially on the coarser grids. However, with the seventh-order and ninth-order WENO-based schemes we observe a significant improvement in accuracy relative to the lower order LES schemes, as revealed by the computed peak in the energy dissipation and by the energy spectrum. Swanson, R. C. and Rumsey, Christopher L. and Rubinstein, Robert and Balakumar, Ponnampalam and Zang, Thomas A. Langley Research Center COMPUTATIONAL FLUID DYNAMICS; HOMOGENEOUS TURBULENCE; ISOTROPIC TURBULENCE; LARGE EDDY SIMULATION; PARAMETERIZATION; DIRECT NUMERICAL SIMULATION; ESSENTIALLY NON-OSCILLATORY SCHEMES; ENERGY SPECTRA; NONLINEARITY; MACH N
Author: W. David McComb
Publisher: OUP Oxford
ISBN: 0191003611
Category : Mathematics
Languages : en
Pages : 429
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Book Description
Fluid turbulence is often referred to as `the unsolved problem of classical physics'. Yet, paradoxically, its mathematical description resembles quantum field theory. The present book addresses the idealised problem posed by homogeneous, isotropic turbulence, in order to concentrate on the fundamental aspects of the general problem. It is written from the perspective of a theoretical physicist, but is designed to be accessible to all researchers in turbulence, both theoretical and experimental, and from all disciplines. The book is in three parts, and begins with a very simple overview of the basic statistical closure problem, along with a summary of current theoretical approaches. This is followed by a precise formulation of the statistical problem, along with a complete set of mathematical tools (as needed in the rest of the book), and a summary of the generally accepted phenomenology of the subject. Part 2 deals with current issues in phenomenology, including the role of Galilean invariance, the physics of energy transfer, and the fundamental problems inherent in numerical simulation. Part 3 deals with renormalization methods, with an emphasis on the taxonomy of the subject, rather than on lengthy mathematical derivations. The book concludes with some discussion of current lines of research and is supplemented by three appendices containing detailed mathematical treatments of the effect of isotropy on correlations, the properties of Gaussian distributions, and the evaluation of coefficients in statistical theories.
Author: Pierre Sagaut
Publisher: Springer
ISBN: 3319731629
Category : Science
Languages : en
Pages : 912
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Book Description
This book provides state-of-the-art results and theories in homogeneous turbulence, including anisotropy and compressibility effects with extension to quantum turbulence, magneto-hydodynamic turbulence and turbulence in non-newtonian fluids. Each chapter is devoted to a given type of interaction (strain, rotation, shear, etc.), and presents and compares experimental data, numerical results, analysis of the Reynolds stress budget equations and advanced multipoint spectral theories. The role of both linear and non-linear mechanisms is emphasized. The link between the statistical properties and the dynamics of coherent structures is also addressed. Despite its restriction to homogeneous turbulence, the book is of interest to all people working in turbulence, since the basic physical mechanisms which are present in all turbulent flows are explained. The reader will find a unified presentation of the results and a clear presentation of existing controversies. Special attention is given to bridge the results obtained in different research communities. Mathematical tools and advanced physical models are detailed in dedicated chapters.
Author: James N. Johnson
Publisher: Springer Science & Business Media
ISBN: 9780387984100
Category : Science
Languages : en
Pages : 544
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Book Description
This collection of classic papers in shock compression science makes available not only some of the most important classic papers on shock waves by Poisson, Rankine, Earnshaw, Riemann, and Hugoniot, which remain important references, but also some pathbreaking papers from the 1940s and 1950s on shocks in solids and fluids by such theorists as Bethe, and Weyl. Although their ideas and results remain of current interest, many of these papers have been hard to find, since the journals in which they were published are not available in many libraries. The editors have also translated papers written in French to make them accessible to a wider audience. This collection is thus not only a valuable historical resource but also a vital reference for those working in the field.
Author: Thomas B. Gatski
Publisher: Oxford University Press
ISBN: 0195355563
Category : Science
Languages : en
Pages : 329
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Book Description
This book provides students and researchers in fluid engineering with an up-to-date overview of turbulent flow research in the areas of simulation and modeling. A key element of the book is the systematic, rational development of turbulence closure models and related aspects of modern turbulent flow theory and prediction. Starting with a review of the spectral dynamics of homogenous and inhomogeneous turbulent flows, succeeding chapters deal with numerical simulation techniques, renormalization group methods and turbulent closure modeling. Each chapter is authored by recognized leaders in their respective fields, and each provides a thorough and cohesive treatment of the subject.
Author: Marcel Lesieur
Publisher: Springer Science & Business Media
ISBN: 1402064357
Category : Technology & Engineering
Languages : en
Pages : 593
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Book Description
Now in its fully updated fourth edition, this leading text in its field is an exhaustive monograph on turbulence in fluids in its theoretical and applied aspects. The authors examine a number of advanced developments using mathematical spectral methods, direct-numerical simulations, and large-eddy simulations. The book remains a hugely important contribution to the literature on a topic of great importance for engineering and environmental applications, and presents a very detailed presentation of the field.
Author: Thomas B. Gatski
Publisher: Springer Science & Business Media
ISBN: 1461227925
Category : Science
Languages : en
Pages : 609
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Book Description
This book contains contributions by former students, colleagues and friends of Professor John L. Lumley, on the occasion of his 60th birthday, in recognition of his enormous impact on the advancement of turbulence research. A variety of experimental, computational and theoretical topics, including turbulence modeling, direct numerical simulations, compressible turbulence, turbulent shear flows, coherent structures and the Proper Orthogonal Decomposition are contained herein. The diversity and scope of these contributions are further acknowledgment of John Lumley's wide ranging influence in the field of turbulence. The large number of contributions by the authors, many of whom were participants in The Lumley Symposium: Recent Developments in Turbulence (held at ICASE, NASA Langley Research Center on November 12 & 13, 1990), has presented us with the unique opportu nity to select a few numerical and theoretical papers for inclusion in the journal Theoretical and Computational Fluid Dynamics for which Professor Lumley serves as Editor. Extended Abstracts of these pa pers are included in this volume and are appropriately marked. The special issue of TCFD will appear this year and will serve as an additional tribute to John Lumley. As is usually the case, the efforts of others have significantly eased our tasks. We would like to express our deep appreciation to Drs. R.
