Download or read book Modeling of Coherent Structure in Boundary Layer Turbulence written by M. T. Landahl and published by . This book was released on 1978 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The large-scale coherent motion associated with turbulent bursting in a boundary layer is studied with the aid of an inviscid model. The space-time evolution of a disturbance of large horizontal dimensions compared to the wall layer thickness is analyzed under the assumption that the mean flow is parallel. The initial velocity field is assumed to be set up by the action of the turbulent stresses produced by a patch of secondary instability. For short and moderate times, the effects of viscosity and pressure are small, and the evolution of the disturbance is conveniently studied with the aid of Lagrangian techniques. The model is able to reproduce qualitatively many of the observed features of the bursting motion such as the formation of longitudinal streaks, the rapid acceleration after initiation of bursting, and the strong y-coherence of the u-fluctuations. In particular, the model demonstrates how action by the mean shear makes the disturbance eventually evolve into a thin internal shear layer, thus making possible the appearance of a new region of inflexional instability and hence burst regeneration-downstream of the original burst. (Author).

Download or read book Turbulent Flows written by G. Biswas and published by CRC Press. This book was released on 2002 with total page 478 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.

Download or read book Modeling Complex Turbulent Flows written by Manuel D. Salas and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence modeling both addresses a fundamental problem in physics, 'the last great unsolved problem of classical physics,' and has far-reaching importance in the solution of difficult practical problems from aeronautical engineering to dynamic meteorology. However, the growth of supercom puter facilities has recently caused an apparent shift in the focus of tur bulence research from modeling to direct numerical simulation (DNS) and large eddy simulation (LES). This shift in emphasis comes at a time when claims are being made in the world around us that scientific analysis itself will shortly be transformed or replaced by a more powerful 'paradigm' based on massive computations and sophisticated visualization. Although this viewpoint has not lacked ar ticulate and influential advocates, these claims can at best only be judged premature. After all, as one computational researcher lamented, 'the com puter only does what I tell it to do, and not what I want it to do. ' In turbulence research, the initial speculation that computational meth ods would replace not only model-based computations but even experimen tal measurements, have not come close to fulfillment. It is becoming clear that computational methods and model development are equal partners in turbulence research: DNS and LES remain valuable tools for suggesting and validating models, while turbulence models continue to be the preferred tool for practical computations. We believed that a symposium which would reaffirm the practical and scientific importance of turbulence modeling was both necessary and timely.

Download or read book Workshop on Coherent Structure of Turbulent Boundary Layers written by Charles Robert Smith and published by . This book was released on 1981 with total page 1116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of the Turbulence Producing Structures in the Boundary Layer written by Stephen Jay Kline and published by . This book was released on 1991 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Coherent Structures Dynamical Systems and Symmetry written by Philip Holmes and published by Cambridge University Press. This book was released on 2012-02-23 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes methods revealing the structures and dynamics of turbulence for engineering, physical science and mathematics researchers working in fluid dynamics.

Download or read book Turbulence and Coherent Structures written by O. Métais and published by Springer. This book was released on 1991 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery of coherent structures among turbulence is the most striking advance in fluid dynamics during these last 20 years. The purpose of this book was to gather the latest results presented at the conference by experimentalists, theoreticians and numerical modellers interested in the origin of these structures, their dynamics and their interaction with small-scale turbulence.

Download or read book Coherent Structures and Wall pressure Fluctuations Modeling in Turbulent Boundary Layers Subjected to Pressure Gradients written by Miloud Alaoui and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow around vehicles creates a turbulent boundary layer in the vicinity of the wall. The turbulent behavior induces pressure fluctuations that make the panels vibrate. These vibrations are then transmitted though the structure of the vehicle and radiate noise inside the cabin. The flow-induced noise levels increase with the speed of the vehicle. For this reason, aircraft manufacturers show a great interest in this topic.There are two objectives for this thesis: understand the mechanisms responsible for the wall-pressure fluctuations and predict this source of aircraft panel excitation.A study of available Large Eddy Simulation (LES) computations was performed. The database consists in simulations of turbulent boundary layer flows submitted to favorable, adverse and zero pressure gradients. This is necessary to understand the nature of the flow over curved geometries such as the aircraft flight deck. The effect of pressure gradients on coherent hairpin structures and hairpin packets could be identified and quantified based on visualization and statistical analysis methods. Linear stochastic estimation of the velocity fields revealed a pair of counter-rotating streamwise vortices above hairpin packets. These vortices have a vorticity opposite to that of the hairpins and an “inverse hairpin” model was proposed.Following the work of Ahn et al. (2010), a stochastic model for wall-pressure spectrum was developed. The idea is to build a stochastic turbulent velocity field using hairpin packets which are subjected to a mean flow. The characteristics of the packets depending on the pressure gradient are based on the analyses of the LES database. The pressure field at the wall is obtained by solving a Poisson equation. The results of the hairpin packet model are compared to numerical and experimental data. Finally, the model is used as input for a Statistical Energy Analysis (SEA) simulation in order to predict the levels of vibrations of panels submitted to a turbulent boundary layer flow over a portion of an aircraft cabin.

Download or read book Simulation and Modeling of Turbulent Flows written by T. B. Gatski and published by Oxford University Press, USA. This book was released on 1996 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Constructive Modeling of Structural Turbulence and Hydrodynamic Instabilities written by Oleg Mikha?lovich Belot?serkovski? and published by World Scientific. This book was released on 2009 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides an original approach in the research of structural analysis of free developed shear compressible turbulence at high Reynolds number on the base of direct numerical simulation (DNS) and instability evolution for ideal medium (integral conservation laws) with approximate mechanism of dissipation (FLUX dissipative monotone ?upwind? difference schemes) and does not use any explicit sub-grid approximation and semi-empirical models of turbulence. Convective mixing is considered as a principal part of conservation law.Appropriate hydrodynamic instabilities (free developed shear turbulence) are investigated from unique point of view. It is based on the concept of large ordered structures with stochastic core of small scale developed turbulence (?turbulent spot?). Decay of ?turbulent spot? are simulated by Monte Carlo method. Proposed approach is based on two hypotheses: statistical independence of the characteristic of large ordered structures (LOS) and small-scale turbulence (ST) ?and? weak influence of molecular viscosity (or more generally, dissipative mechanism) on properties of large ordered structures.Two versions of instabilities, due to Rayleigh-Taylor and Richtmyer-Meshkov are studied detail by the three-dimensional calculations, extended to the large temporal intervals, up to turbulent stage and investigation turbulent mixing zone (TMZ).The book covers both the fundamental and practical aspects of turbulence and instability and summarizes the result of numerical experiments conducted over 30 years period with direct participation of the author.In the book are cited the opinions of the leading scientists in this area of research: Acad. A S Monin (Russia), Prof. Y Nakamura (Japan, Nagoya University) and Prof. F Harlow (USA, Los-Alamos).

Download or read book A Theoretical Model of the Coherent Structure of a Flat Plate Turbulent Boundary Layer written by Z. Zhang and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coherent Structure Reflective Turbulent Viscous Flow Modeling written by Gustave J. Hokenson and published by . This book was released on 1987 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coherent Flow Structures at Earth s Surface written by Jeremy G. Venditti and published by John Wiley & Sons. This book was released on 2013-08-28 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: An expert review of recent progress in the study of turbulent flows with a focus on recently identified organized structures. This book reviews the recent progress in the study of the turbulent flows that sculpt the Earth’s surface, focusing in particular on the organized structures that have been identified in recent years within turbulent flows. These coherent flow structures can include eddies or vortices at the scale of individual grains, through structures that scale with the flow depth in rivers or estuaries, to the large-scale structure of flows at the morphological or landform scale. These flow structures are of wide interest to the scientific community because they play an important role in fluid dynamics and influence the transport, erosion and deposition of sediment and pollutants in a wide variety of fluid flow environments. Scientific knowledge of these structures has improved greatly over the past 20 years as computational fluid dynamics has come to play an increasing important part in building our understanding of coherent flow structures across a broad range of scales. Chapters comprise a series of major, invited papers and a selection of the most novel, innovative papers presented at the second Coherent Flow Structures Conference held August 3-5, 2011 at Simon Fraser University in Burnaby, British Columbia. Chapters focus on six major themes: Dynamics of coherent flow structures (CFS) in geophysical flows Interaction of turbulent flows, vegetation and ecological habitats Coherent structure of atmospheric flows Numerical modeling of coherent flow structures Turbulence in open channel flows Coherent flow structures, sediment transport and morphological feedbacks.

Download or read book Coherent Structure of a Turbulent Boundary Layer in a Convected Reference Frame written by C. R. Smith and published by . This book was released on 1977 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an interim annual report for an ongoing research program studying coherent structure in turbulent boundary layers. The design and development of a water channel facility for use in flow visualization studies of coherent turbulent boundary structure is described. The particularly unique aspects of this facility include the incorporation of (1) a moving reference (viewing) platform for study of relative motion effects and (2) a closed circuit television monitoring and recording system. Preliminary flow visualization results are presented for both a fixed and moving reference frame, and a tentative vortex-loop model of coherent turbulent boundary layer structure is proposed. Computer simulations of a transverse structure in a turbulent boundary layer are presented showing a remarkable similarity with experimental flow visualization results. Research directions for the following year are outlined. (Author).

Download or read book Turbulence Coherent Structures Dynamical Systems and Symmetry written by Philip Holmes and published by Cambridge University Press. This book was released on 1996-10-10 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: First-time paperback of successful book on turbulence by very well known authors.

Download or read book Turbulence Numerical Analysis Modelling and Simulation written by William Layton and published by MDPI. This book was released on 2018-05-04 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Turbulence: Numerical Analysis, Modelling and Simulation" that was published in Fluids

Download or read book Further Developments in Turbulence Management written by K. Krishna Prasad and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thrust of modern research on turbulence in fluids is concerned with coherent structures and modelling. Riblets have been shown to reduce drag, and the papers presented in this volume tackle the main question of the mechanism responsible for this behaviour in turbulent flow. The contributions in this volume were presented at the Sixth Drag Reduction Meeting held at Eindhoven during November 1991. This volume will be a useful reference work for engineers, physicists and applied mathematicians interested in the topic of fluid turbulence.