Download or read book Evolution of Hairpin Vortices in a Shear Flow written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-03 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experimental studies suggest that the hairpin vortex plays an important (and perhaps dominant) role in the dynamics of turbulent flows near walls. In this study a numerical procedure is developed to allow the accurate computation of the trajectory of a 3-D vortex having a small core radius. For hairpin vortices which are convected in a shear flow above a wall, the calculated results show that a 2-D vortex containing a small 3-D disturbance distorts into a complex shape with subsidiary hairpin vortices forming outboard of the original hairpin vortex. As the vortex moves above the wall, it induces unsteady motion in the viscous flow near the wall: numerical solutions suggest that the boundary-layer flow near the wall will ultimately erupt in response to the motion of the hairpin vortex and in the process a secondary hairpin vortex will be created. The computer results agree with recent experimental investigations. Hon, T.-L. and Walker, J. D. A. Glenn Research Center NASA ORDER C-99066-G; RTOP 505-62-21...
Download or read book Evolution of Hairpin Vortices in a Shear Flow written by T.-L. Hon and published by . This book was released on 1988 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analysis of the Motion and Effects of Hairpin Vortices written by Thon-Lon Hon and published by . This book was released on 1987 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies suggest that the hairpin vortex plays an important, possibly dominant, role in the dynamics of turbulent flows near walls. This study addresses the following topics of the motion of hairpin vortices near solid walls on a theoretical basis: the nature of the evolution of hairpin vortices in a shear flow; the type of flow induced near a wall by a convected hairpin vortex; the character of the viscous response near a wall to the hairpin vortex motion; and the nature of the interaction of 2 hairpin vortices. A numerical procedure is developed to allow accurate evaluation of the trajectory of a 3-dimensional vortex for vortices having small cores. The integration method is based on a numerical approximation to the Biot-Savart integral; most existing vortex calculation methods have severe stability problems for vortices with small cores. These problems are overcome with the present method and technique is applied to compute the evolution of convected vortex loops and hairpin vortices, both in uniform flow and in shear flow above a wall. For hairpin vortices evolving in a shear flow, a regenerative process is observed wherein secondary hairpin vortices form outboard of the original hairpin vortex in a manner consistent with experimental observations. Calculations for 2 hairpin vortices, initially close to one another in a shear flow, show that the vortices interact to reinforce one another. Simulations carried out to compute the evolution of hydrogen bubble lines as a hairpin vortex passes show that such vortices can give rise to wall layer streaks.
Download or read book Hairpin Vortices Singularities and Transition to Turbulence in Three dimensional Shear Flows written by and published by . This book was released on 1990 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the evolution of a transversely perturbed co-flowing jet in a triply periodic box by means of a second-order projection method for the three-dimensional Euler equations. Advection-diffusion equations are solved without enforcing the incompressibility constraint, and the resulting velocity field is projected onto a divergence-free subspace. The method is unique in its treatment of nonlinear advection; it incorporates a second-order, upstream-centered differencing procedure that provides a robust treatment of nonsmooth data without introducing spurious oscillations, even in the limit of vanishing viscosity. The flow is visualized by following the evolution of a tracer function initialized on the surface of the tube. We also carry out a volume rendering of the vorticity field with an opacity profile and color map which shows that hairpin vortices abound and that vorticity intensifies greatly at their tips. We present strong numerical evidence that the vorticity becomes unbounded, and show that accompanying the onset of the singularity is a decay in the mean kinetic energy. Following the onset, a Kolmogorov (k−53) range emerges in the energy spectrum.
Download or read book Liutex and Its Applications in Turbulence Research written by Chaoqun Liu and published by Academic Press. This book was released on 2020-10-29 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liutex and Its Applications in Turbulence Research reviews the history of vortex definition, provides an accurate mathematical definition of vortices, and explains their applications in flow transition, turbulent flow, flow control, and turbulent flow experiments. The book explains the term "Rortex" as a mathematically defined rigid rotation of fluids or vortex, which could help solve many longstanding problems in turbulence research. The accurate mathematical definition of the vortex is important in a range of industrial contexts, including aerospace, turbine machinery, combustion, and electronic cooling systems, so there are many areas of research that can benefit from the innovations described here. This book provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence. Important theory and methodologies used for developing these laws are described in detail, including: the classification of the conventional turbulent boundary layer concept based on proper velocity scaling; the methodology for identification of the scales of velocity, temperature, and length needed to establish the law; and the discovery, proof, and strict validations of the laws, with both Reynolds and Prandtl number independency properties using DNS data. The establishment of these statistical laws is important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence. Provides an accurate mathematical definition of vortices Provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence Explains the term “Rortex as a mathematically defined rigid rotation of fluids or vortex Covers the statistical laws important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence
Download or read book Fluid Vortices written by Sheldon Green and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 905 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid Vortices is a comprehensive, up-to-date, research-level overview covering all salient flows in which fluid vortices play a significant role. The various chapters have been written by specialists from North America, Europe and Asia, making for unsurpassed depth and breadth of coverage. Topics addressed include fundamental vortex flows (mixing layer vortices, vortex rings, wake vortices, vortex stability, etc.), industrial and environmental vortex flows (aero-propulsion system vortices, vortex-structure interaction, atmospheric vortices, computational methods with vortices, etc.), and multiphase vortex flows (free-surface effects, vortex cavitation, and bubble and particle interactions with vortices). The book can also be recommended as an advanced graduate-level supplementary textbook. The first nine chapters of the book are suitable for a one-term course; chapters 10--19 form the basis for a second one-term course.
Download or read book Evolution of a Curved Vortex Filament Into a Vortex Ring written by and published by . This book was released on 1985 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Behavior of Three Dimensional Vortices Relevant to Turbulent Boundary Layers written by C. R. Smith and published by . This book was released on 1987 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent accomplishments are reviewed for a research program employing combined analytical-experiments techniques to study the three dimensional characteristics and behavior of vortex motions associated with the turbulence production process in turbulent boundary layers. Progress is described in the development of a new image processing technique which allows the derivation of quantitative data from flow visualization images. The method is used to search for the role of hairpin vortices in the turbulence production process. In the analytical portion of the study, calculations have been carried out to compute the evolution of a hairpin vortex in a shear flow; the interaction of a pair of hairpins has been examined as well as the viscous response at a wall due to the motion of a hairpin vortex. Comparison of these computer simulations with the experimental studies is very encouraging. Computations for the evolving flow between wall layer streaks during a typical cycle in the wall layer of a turbulent boundary layer have also been carried out; these studies show two possible routes to breakdown of the wall layer flow leading to the production process. Keywords: Turbulent boundary layers; Hairpin vortices; Vortex motion.
Download or read book Vortical Flows written by Jie-Zhi Wu and published by Springer. This book was released on 2015-06-23 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a comprehensive and intensive book for graduate students in fluid dynamics as well as scientists, engineers and applied mathematicians. Offering a systematic introduction to the physical theory of vortical flows at graduate level, it considers the theory of vortical flows as a branch of fluid dynamics focusing on shearing process in fluid motion, measured by vorticity. It studies vortical flows according to their natural evolution stages,from being generated to dissipated. As preparation, the first three chapters of the book provide background knowledge for entering vortical flows. The rest of the book deals with vortices and vortical flows, following their natural evolution stages. Of various vortices the primary form is layer-like vortices or shear layers, and secondary but stronger form is axial vortices mainly formed by the rolling up of shear layers. Problems are given at the end of each chapter and Appendix, some for helping understanding the basic theories, and some involving specific applications; but the emphasis of both is always on physical thinking.
Download or read book Structure of Turbulence and Drag Reduction written by Albert Gyr and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 617 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1976 a similar titled IUTAM Symposium (Structure of Turbulence and Drag Reduction) was held in Washington . However, the progress made during the last thirteen years as weil as the much promising current research desired a second one this year. In Washington drag reduction by additives and by direct manipulation of the walls (compliant walls and heated surfaces) were discussed. In the meantime it became evident that drag reduction also occurs when turbulence is influenced by geometrical means, e.g. by influencing the pressure distribution by the shape of the body (airfoils) or by the introduction of streamwise perturbances on a body (riblets). In the recent years turbulence research has seen increasing attention being focused on the investigation of coherent structures, mainly in Newtonian fluids. We all know that these structures are a significant feature of turbulent flows, playing an important role in the energy balance in such flows. However their place in turbulence theories as weil as the factors influencing their development are still poorly understood. Consequently, the investigation of phenomena in which the properties of coherent structures are alte red provides a promising means of improving our understanding of turbulent flows in general.
Download or read book Vorticity and Turbulence Effects in Fluid Structure Interaction written by Maurizio Brocchini and published by WIT Press. This book was released on 2006 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a collection of 11 research and review papers which have been contributed by each research unit joining the MIUR funded project: "Influence of vorticity and turbulence in interactions of water bodies with their boundary elements and effects on hydraulic design". The book features state-of-the-art Italian research devoted to the topic of fluid-structure interaction.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Advances in Boundary Layer Theory written by Alfred Kluwick and published by Springer. This book was released on 2014-05-04 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in boundary-layer theory have shown how modern analytical and computational techniques can and should be combined to deepen the understanding of high Reynolds number flows and to design effective calculation strategies. This is the unifying theme of the present volume which addresses laminar as well as turbulent flows.
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1990 with total page 1482 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advances in Fluid Mechanics XII written by S. Hernández and published by WIT Press. This book was released on 2018-10-30 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: Containing papers from the 12th International Conference on Advances in Fluid Mechanics, this book covers a wide range of topics including basic formulations and their computer modelling as well as the relationship between experimental and analytical results. The emphasis is on new applications and research currently in progress. The field of fluid mechanics is vast and has numerous and diverse applications. The contained research works discuss new studies in fluid mechanics and present the latest applications in the field. A wide range of topics are covered including, Computational methods; Boundary elements and other mesh reduction methods; Fluid structure interaction; Cooling of electronic devices; Environmental fluid dynamics; Industrial applications; Energy systems; Nano and micro fluids; Turbulent and complex flows; Jets; Droplet and spray dynamics; Bubble dynamics; Multiphase fluid flow; Pumping and fluid transportation; Experimental measurements; Rheology; Chemical reaction flow; Hydroelectromagnetic flow; High speed flow; Wave theory; Energy conversion systems.
Download or read book Computational Science ICCS 2007 written by Yong Shi and published by Springer. This book was released on 2007-07-13 with total page 1310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part of a four-volume set, this book constitutes the refereed proceedings of the 7th International Conference on Computational Science, ICCS 2007, held in Beijing, China in May 2007. The papers cover a large volume of topics in computational science and related areas, from multiscale physics to wireless networks, and from graph theory to tools for program development.
Download or read book Laminar Turbulent Transition written by H.F. Fasel and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 703 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origins of turbulent flow and the transition from laminar to turbulent flow are among the most important unsolved problems of fluid mechanics and aerodynamics. Besides being a fundamental question of fluid mechanics, there are any number of applications for information regarding transition location and the details of the subsequent turbulent flow. The JUT AM Symposium on Laminar-Turbulent Transition, co-hosted by Arizona State University and the University of Arizona, was held in Sedona, Arizona. Although four previous JUT AM Symposia bear the same appellation (Stuttgart 1979, Novosibirsk 1984, Toulouse 1989, and Sendai 1994) the topics that were emphasized at each were different and reflect the evolving nature of our understanding of the transition process. The major contributions of Stuttgart 1979 centered on nonlinear behavior and later stages of transition in two-dimensional boundary layers. Stability of closed systems was also included with Taylor vortices in different geometries. The topics of Novosibirsk 1984 shifted to resonant wave interactions and secondary instabilities in boundary layers. Pipe- and channel-flow transition were discussed as model problems for the boundary layer. Investigations of free shear layers were presented and a heavy dose of supersonic papers appeared for the first time. The character of Toulouse 1989 was also different in that 3-D boundary layers, numerical simulations, streamwise vortices, and foundation papers on receptivity were presented. Sendai 1994 saw a number of papers on swept wings and 3-D boundary layers. Numerical simulations attacked a broader range of problems.
