Download or read book Identifying Coherent Motions in Near Surface Turbulence written by Alex Anderson and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Near-surface turbulence is responsible for around 70% of the fluxes of heat, momentum, and mass between Earth's surface and its atmosphere and provides important boundary conditions for atmospheric dynamics. To improve the modeling of this turbulence and the fluxes it carries, it is important to understand the microscale coherent structures and associated microfronts of the turbulent motions. In the presence of mean shear, the turbulent mixing of air with different momentum causes horizontal convergence and combines with existing temperature stratification to create temperature microfronts in time series. In this work, temperature microfronts are identified using sonic anemometer data ranging from 10 to 29 meters above the surface during turbulent periods from the Canopy Horizontal Array Turbulence Study (CHATS) from March to June 2007. Each temperature microfront is characterized by a sharp temperature drop following a gradual temperature increase. Temperature and time scales derived from the temperature standard deviation and integral time scale are used to develop new identification criteria of temperature microfronts that are more data dependent and objective. The temperature time series is combined with an analysis of quiescent periods and the velocity components to identify the passage of individual temperature burst events. Using these criteria, 44 initial events were identified and categorized further into three categories. The new criteria are successful in refining microfront characteristics and automating the identification process to objectively extract individual burst events.
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 Free Surface Turbulence written by Rohit Gupta and published by . This book was released on 1998 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence in Fluids written by Marcel Lesieur and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence is a dangerous topic which is often at the origin of serious fights in the scientific meetings devoted to it since it represents extremely different points of view, all of which have in common their complexity, as well as an inability to solve the problem. It is even difficult to agree on what exactly is the problem to be solved. Extremely schematically, two opposing points of view have been ad vocated during these last twenty years: the first one is "statistical", and tries to model the evolution of averaged quantities of the flow. This com munity, which has followed the glorious trail of Taylor and Kolmogorov, believes in the phenomenology of cascades, and strongly disputes the possibility of any coherence or order associated to turbulence. On the other bank of the river stands the "coherence among chaos" community, which considers turbulence from a purely deterministic po int of view, by studying either the behaviour of dynamical systems, or the stability of flows in various situations. To this community are also associated the experimentalists who seek to identify coherent structures in shear flows.
Download or read book Turbulence and Related Phenomena written by Regis Barille and published by BoD – Books on Demand. This book was released on 2019-04-17 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents some of the most important results concerning atmospheric turbulence and some of its effects on the propagation of a light beam. Atmospheric turbulence causes fluctuations in both the intensity and the phase of the beam and still must be understood and modelized for applications in photonics or environmental metrology. The future of free-space optical (FSO) communication through atmospheric turbulence channels is especially of interest and research on high bit-rate communications attracts more and more interest as an alternative to radio links because of bandwidth, spectrum, and security issues. Some of the current solutions for improving FSO communications are presented in this book.
Download or read book Principles of Turbulence Control written by Baochun Fan and published by John Wiley & Sons. This book was released on 2022-05-17 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the mathematical techniques for turbulence control in a form suitable for inclusion in an engineering degree program at both undergraduate and postgraduate levels whilst also making it useful to researchers and industrial users of the concepts. It uses a mix of theory, computation and experimental results to present and illustrate the methodologies. It is based on the three part structure, wall turbulence, open loop control and feedback control with emphasis on optimal control methodologies. The book also includes an introduction of basic principles and fundamentals followed by a chapter on the structure of wall turbulence with emphasis on coherent structures. Elsewhere there is focus on control methods of wall turbulence by manipulating the boundaries though their motion and by applying control forces throughout the flow volume. The last two chapters will describe the linear and non-linear optimal controls. This integrated approach will help not only researchers interested in the topic but also graduate or advanced undergraduate students in their course work.
Download or read book The Near Surface Layer of the Ocean written by Alexander Soloviev and published by Springer Science & Business Media. This book was released on 2006-02-21 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: Until the 1980s, a tacit agreement among many physical oceanographers was that nothing deserving attention could be found in the upper few meters of the ocean. The lack of adequete knowledge about the near-surface layer of the ocean was mainly due to the fact that the widely used oceanographic instruments (such as bathythermographs, CTDs, current meters, etc.) were practically useless in the upper few meters of the ocean. Interest in the ne- surface layer of the ocean rapidly increased along with the development of remote sensing techniques. The interpretation of ocean surface signals sensed from satellites demanded thorough knowledge of upper ocean processes and their connection to the ocean interior. Despite its accessibility to the investigator, the near-surface layer of the ocean is not a simple subject of experimental study. Random, sometimes huge, vertical motions of the ocean surface due to surface waves are a serious complication for collecting quality data close to the ocean surface. The supposedly minor problem of avoiding disturbances from ships’ wakes has frustrated several generations of oceanographers attempting to take reliable data from the upper few meters of the ocean. Important practical applications nevertheless demanded action, and as a result several pioneering works in the 1970s and 1980s laid the foundation for the new subject of oceanography – the near-surface layer of the ocean.
Download or read book Advanced Approaches in Turbulence written by Paul Durbin and published by Elsevier. This book was released on 2021-07-24 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Approaches in Turbulence: Theory, Modeling, Simulation and Data Analysis for Turbulent Flows focuses on the updated theory, simulation and data analysis of turbulence dealing mainly with turbulence modeling instead of the physics of turbulence. Beginning with the basics of turbulence, the book discusses closure modeling, direct simulation, large eddy simulation and hybrid simulation. The book also covers the entire spectrum of turbulence models for both single-phase and multi-phase flows, as well as turbulence in compressible flow. Turbulence modeling is very extensive and continuously updated with new achievements and improvements of the models. Modern advances in computer speed offer the potential for elaborate numerical analysis of turbulent fluid flow while advances in instrumentation are creating large amounts of data. This book covers these topics in great detail. Covers the fundamentals of turbulence updated with recent developments Focuses on hybrid methods such as DES and wall-modeled LES Gives an updated treatment of numerical simulation and data analysis
Download or read book New Approaches and Concepts in Turbulence written by T. Dracos and published by Birkhäuser. This book was released on 2012-12-06 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the proceedings of a colloquium held in Monte Verit from September 9-13, 1991. Special care has been taken to devote adequate space to the scientific discussions, which claimed about half of the time available. Scientists from all over the world presented their views on the importance of kinematic properties, topology and fractal geometry, and on the dynamic behaviour of turbulent flows. They debated the importance of coherent structures and the possibility to incorporate these in the statistical theory of turbulence, as well as their significance for the reduction of the degrees of freedom and the prospective of dynamical systems and chaos approaches to the problem of turbulence. Also under discussion was the relevance of these new approaches to the study of the instability and the origin of turbulence, and the importance of numerical and physical experiments in improving the understanding of turbulence.
Download or read book Turbulent Shear Flows 5 written by Franz Durst and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Coherent Dynamics and Turbulence Dynamics in Model Geophysical Flow written by Lei Fang and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: My Ph.D. study consists of three portions -- turbulence dynamics, coherent dynamics, and two newly developed analytic tools to probe turbulence dynamics and coherent dynamics in any generic flows. First, we study the turbulent dynamics in the model geophysical flow because the majority of fluid flows in nature and engineering applications are turbulent. Turbulent flows are distinct because they display a characteristic cascade of energy, which is typically described in an abstract way. My research recasts the turbulent energy cascade as a mechanical process so that, as with any energy flux, it can be interpreted as the result of the action of the turbulent stress against the rate of strain. Using the mechanical model and with the help of filter space techniques (FST), we define the efficiency of turbulence cascades based on the geometry of stress and rate of strain for the first time in the field. Moreover, our work reveals that the advection is a missing piece in the well- known "thinning mechanism". We find that excessive advection dampens the cascade efficiency by disrupting the delicate angle alignment between stress and rate of strain that is required to transfer energy. Additionally, we utilize FST to study decay turbulence. These works can eventually lead to new strategies for turbulence modeling. Second, transport phenomena are complicated but not random. Anyone who has observed ocean surface currents realizes that the flow appears to be composed of coherent motions that persist in time. Examples include eddies and jets that move in the flow for a longer time than the background flow. Such coherent structures are spatiotemporally compact regions of the flow that are thought to be important for determining mixing and transport. Geophysical flows can be well approximated as two-dimensional on large scales. And two-dimensional flows, in turn, are particularly prone to producing a range of coherent structures. However, how such structures interact with lateral boundaries such as coastlines, and bottom boundaries such as nonuniform bathymetry, is not well understood. A laboratory two-dimensional flow and Lagrangian coherent structure methods are used to study these questions. The research characterizes the different effects of canonical lateral boundary shapes and bottom bathymetry. Furthermore, we finds reduced transport across a bathymetric interface and describes this reduced transport in terms of the "porous transport barrier separating the two regions. The results can have implications in the siting of coastal facilities that must ensure the appropriate mixing for minimizing environmental impacts and benefit precise control to aquaculture. Third, I propose the two new tools which redefined what it means of coherence. Traditionally, coherent structures are perceived as spatiotemporally compact regions of the flow. By elegant redefinition, the coherent structures can tackle many more interesting and important engineering problems that include but are not limited to revealing information content in complex flows, effective compressing of flow data, recovering missing measurements, and connecting turbulent dynamics and kinematics. We redefine coherence based on linear predictability, i.e., perceiving coherent structures as regions that were highly predictable by knowing only a small subset of them. The research results in two tools: Linear Neighborhood (LN) and Dynamical Linear Neighborhood (DLN), which have shown promising results in the problems mentioned above.
Download or read book Turbulent Flow Structure Near Walls written by J. D. A. Walker and published by . This book was released on 1991 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, progress has been made in determining the nature of turbulent flow near walls. Many of these advances, which have occurred through new experimental methodologies, direct numerical simulations, and new theoretical developments, are described in this volume.
Download or read book Liutex and Third Generation of Vortex Identification written by Yiqian Wang and published by Springer Nature. This book was released on 2023-03-21 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings highlights the applications of the newly introduced physical quantity Liutex in hydrodynamics and aerodynamics. Liutex is used to represent the fascinating rotational motion of fluids, i.e., the vortex. Ubiquitously seen in nature and engineering applications, the definition of vortices has been elusive. The Liutex vector provides a unique and systematic description of vortices. The proceedings collects papers presented in the invited workshop "Liutex and Third Generation of Vortex Identification for Engineering Applications" from Aerospace and Aeronautics World Forum 2021. The papers in this book cover both the theoretical aspects of Liutex and many applications in hydrodynamics and aerodynamics. The proceedings is a good reference for researchers in fluid mechanics who are interested in learning about the wide scope of applications of Liutex and using it to develop a new understanding of their research subjects.
Download or read book Turbulent Shear Flows I written by F. Durst and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present book contains papers that have been selected from contributions to the First International Symposium on Turbulent Shear Flows which was held from the 18th to 20th April 1977 at The Pennsylvania State University, University Park, Pennsylvania, USA. Attend ees from close to 20 countries presented over 100 contributions at this meeting in which many aspects of the current activities in turbulence research were covered. Five topics received particular attention at the Symposium: Free Flows Wall Flows Recirculating Flows Developments in Reynolds Stress Closures New Directions in Modeling This is also reflected in the five chapters of this book with contributions from research workers from different countries. Each chapter covers the most valuable contributions of the conference to the particular chapter topic. Of course, there were many additional good con tributions to each subject at the meeting but the limitation imposed on the length of this volume required that a selection be made. The realization of the First International Symposium on Turbulent Shear Flows was p- sible by the general support of: U. S. Army Research Office U. S. Navy Research Office Continuing Education Center of The Pennsylvania State University The conference organization was carried out by the organizing committee consisting of: F. Durst, Universitat Karlsruhe, Karlsruhe, Fed. Rep. of Germany V. W. Goldschmidt, Purdue University, West Lafayette, Ind. , USA B. E. Launder, University of California, Davis, Calif. , USA F. W. Schmidt, Pennsylvania State University, University Park, Penna.
Download or read book Eddy Structure Identification in Free Turbulent Shear Flows written by J.P. Bonnet and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 504 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.
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.
Download or read book Marine Turbulence written by Helmut Z. Baumert and published by Cambridge University Press. This book was released on 2005-04-04 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives a comprehensive overview of marine turbulence and mixing for students, scientists, engineers.
