Download or read book Unsteady Fluid Mechanics of Annular Swirling Shear Layers written by David Dunham and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast majority of gas turbine combustor systems employ swirl injectors to produce a central toroidal recirculation zone (CTRZ) which entrains and recirculates a portion of the hot combustion gases to provide continuous ignition to the incoming air-fuel mix. In addition to these primary functions, swirl injectors often generate multiple aerodynamic instability modes which are helical in nature with characteristic frequencies that can differ by many orders of magnitude. If any of these frequencies are consistent with prevalent acoustic modes within the combustor there is a potential for flow-acoustic coupling which may reinforce acoustic oscillations and drive combustion instabilities via the Rayleigh criterion. The aerodynamic performance of the swirl injector is thus of great practical importance to the design and development of combustion systems and there is a strong desire within industry for reliable computational methods that can predict this highly unsteady behaviour. This assessment can be made under isothermal conditions which avoids the complex interactions that occur in reacting flow. The goal of the present work was to compare and contrast the performance of Unsteady Reynolds- Averaged Navier-Stokes (URANS) and Large-Eddy Simulation (LES) CFD methodologies for a combustion system equipped with a derivative of an industrial Turbomeca swirl injector as this exhibits similar unsteady aerodynamic behaviour under reacting and isothermal conditions. The influence of the level of swirl, SN = 0.51-0.8, was first investigated experimentally using Particle Image Velocimetry (PIV) by varying the inlet swirl vane angle. Based on a qualitative assessment of instantaneous velocity data, and a range of coherent structure eduction techniques, it was found that ®1 = 30± (SN 1/4 0.8) would be the most challenging test case for LES and URANS as this contained near and far-field instability modes that differ in frequency by around two orders of magnitude and the highest levels of normal Reynolds-stress anisotropy. Based on extensive simulations performed with both in-house (LULES and Delta) and commercial (Fluent) CFD codes it was found that, despite the relative modest computational cost of URANS which is between one-third (RST) to an order of magnitude (k-2) less than that demanded by LES, only LES captures the all-important frequency content in accordance with experimental evidence and, thus, only LES can be recommended for use in swirl injector flows. The increased cost is believed to be an absolutely worthwhile expense because of the high fidelity of the predicted results in the important area of flow instabilities.
Download or read book Unsteady Combustor Physics written by Tim C. Lieuwen and published by Cambridge University Press. This book was released on 2012-08-27 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.
Download or read book The Fluid Mechanics of Swirling Flow Within Annular Regions written by Robert Milano and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics of Transitional Shear Flows written by Andrey V. Boiko and published by Springer Science & Business Media. This book was released on 2011-09-15 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting from fundamentals of classical stability theory, an overview is given of the transition phenomena in subsonic, wall-bounded shear flows. At first, the consideration focuses on elementary small-amplitude velocity perturbations of laminar shear layers, i.e. instability waves, in the simplest canonical configurations of a plane channel flow and a flat-plate boundary layer. Then the linear stability problem is expanded to include the effects of pressure gradients, flow curvature, boundary-layer separation, wall compliance, etc. related to applications. Beyond the amplification of instability waves is the non-modal growth of local stationary and non-stationary shear flow perturbations which are discussed as well. The volume continues with the key aspect of the transition process, that is, receptivity of convectively unstable shear layers to external perturbations, summarizing main paths of the excitation of laminar flow disturbances. The remainder of the book addresses the instability phenomena found at late stages of transition. These include secondary instabilities and nonlinear features of boundary-layer perturbations that lead to the final breakdown to turbulence. Thus, the reader is provided with a step-by-step approach that covers the milestones and recent advances in the laminar-turbulent transition. Special aspects of instability and transition are discussed through the book and are intended for research scientists, while the main target of the book is the student in the fundamentals of fluid mechanics. Computational guides, recommended exercises, and PowerPoint multimedia notes based on results of real scientific experiments supplement the monograph. These are especially helpful for the neophyte to obtain a solid foundation in hydrodynamic stability. To access the supplementary material go to extras.springer.com and type in the ISBN for this volume.
Download or read book Unsteady Combustor Physics written by Tim C. Lieuwen and published by Cambridge University Press. This book was released on 2021-10-21 with total page 533 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore a unified treatment of the dynamics of combustor systems, including acoustics, fluid mechanics, and combustion in a single rigorous text. This updated new edition features an expansion of data and experimental material, updates the coverage of flow stability, and enhanced treatment of flame dynamics. Addresses system dynamics of clean energy and propulsion systems used in low emissions systems. Synthesizing the fields of fluid mechanics and combustion into a coherent understanding of the intrinsically unsteady processes in combustors. This is a perfect reference for engineers and researchers in fluid mechanics, combustion, and clean energy.
Download or read book Unsteady Shear Disturbances Within a Two Dimensional Stratified Flow written by and published by . This book was released on 1992 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Turbulent Shear Flows written by International Union of Theoretical and Applied Mechanics and published by Springer. This book was released on 1981 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structure of Turbulent Shear Flow written by A. A. R. Townsend and published by Cambridge University Press. This book was released on 1976 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.
Download or read book Turbulent Shear Flows 3 written by L.J.S. Bradbury and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: In spite of intensive efforts over many decades, the problem of turbulence remains as challenging as ever and the number of papers, books and conferences on this topic con tinues to grow. As experimental techniques and computing power have developed, the breadth of investigations into the structure and development of turbulent flows has in creased to encompass many diverse fields of application in engineering, physics, biolo gy and so on. As a consequence, it is now very difficult for a single research worker to keep in touch with the many developments that are taking place in turbulence. One of the few opportunities for obtaining some overall view of the subject arises from large international symposia on turbulence and, although they have some drawbacks, it is this opportunity that is one of their main merits. The International Symposium on Turbulent Shear Flows has now been held on three occasions and they seem to be established as a major opportunity for papers on a very diverse range of topics to be presented at a single meeting. This volume is a collec tion of papers from the third symposium that was held at the University of California, Davis from 9-11 September 1981. The papers are divided into four sections entitled Wall Flows, Scalar Transport, Recirculating Flows and Fundamentals. This collection represents about a third of the total number of papers presented.
Download or read book Turbulent Shear Flows 8 written by F. Durst and published by Springer. This book was released on 1993 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains a selection of the papers presented at the Eighth Symposium on Turbulent Shear Flows held at the Technical University of Munich, 9-11 September 1991. The first of these biennial international symposia was held at the Pennsylvania State Uni versity, USA, in 1977; subsequent symposia have been held at Imperial College, London, England; the University of California, Davis, USA; the University of Karlsruhe, Ger many; Cornell University, Ithaca, USA; the Paul Sabatier University, Toulouse, France; and Stanford University, California, USA. The purpose of this series of symposia is to provide a forum for the presentation and discussion of new developments in the field of turbulence, especially as related to shear flows of importance in engineering and geo physics. From the 330 extended abstracts submitted for this symposium, 145 papers were presented orally and 60 as posters. Out of these, we have selected twenty-four papers for inclusion in this volume, each of which has been revised and extended in accordance with the editors' recommendations. The following four theme areas were selected after consideration of the quality of the contributions, the importance of the area, and the selection made in earlier volumes: - wall flows, - separated flows, - compressibility effects, - buoyancy, rotation, and curvature effects. As in the past, each section corresponding to the above areas begins with an introduction by an authority in the field that places the individual contributions in context with one another and with related research.
Download or read book The Mechanics of Turbulence written by and published by . This book was released on 1964 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Origin of Turbulence in Near Wall Flows written by A.V. Boiko and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Origin of Species Charles Darwin The origin of turbulence in fluids is a long-standing problem and has been the focus of research for decades due to its great importance in a variety of engineering applications. Furthermore, the study of the origin of turbulence is part of the fundamental physical problem of turbulence description and the philosophical problem of determinism and chaos. At the end of the nineteenth century, Reynolds and Rayleigh conjectured that the reason of the transition of laminar flow to the 'sinuous' state is in stability which results in amplification of wavy disturbances and breakdown of the laminar regime. Heisenberg (1924) was the founder of linear hydrody namic stability theory. The first calculations of boundary layer stability were fulfilled in pioneer works of Tollmien (1929) and Schlichting (1932, 1933). Later Taylor (1936) hypothesized that the transition to turbulence is initi ated by free-stream oscillations inducing local separations near wall. Up to the 1940s, skepticism of the stability theory predominated, in particular due to the experimental results of Dryden (1934, 1936). Only the experiments of Schubauer and Skramstad (1948) revealed the determining role of insta bility waves in the transition. Now it is well established that the transition to turbulence in shear flows at small and moderate levels of environmental disturbances occurs through development of instability waves in the initial laminar flow. In Chapter 1 we start with the fundamentals of stability theory, employing results of the early studies and recent advances.
Download or read book The Nonlinear Evolution of Modes on Unstable Stratified Shear Layers written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1993 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Swirl Flows written by Ashwani K. Gupta and published by Routledge. This book was released on 1984 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radial Flow Turbocompressors written by Michael Casey and published by Cambridge University Press. This book was released on 2021-06-10 with total page 789 pages. Available in PDF, EPUB and Kindle. Book excerpt: An introduction to the theory and engineering practice that underpins the component design and analysis of radial flow turbocompressors. Drawing upon an extensive theoretical background and years of practical experience, the authors provide descriptions of applications, concepts, component design, analysis tools, performance maps, flow stability, and structural integrity, with illustrative examples. Features wide coverage of all types of radial compressor over many applications unified by the consistent use of dimensional analysis. Discusses the methods needed to analyse the performance, flow, and mechanical integrity that underpin the design of efficient centrifugal compressors with good flow range and stability. Includes explanation of the design of all radial compressor components, including inlet guide vanes, impellers, diffusers, volutes, return channels, de-swirl vanes and side-streams. Suitable as a reference for advanced students of turbomachinery, and a perfect tool for practising mechanical and aerospace engineers already within the field and those just entering it.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1971 with total page 776 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulent Flows in Engineering written by A. J. Reynolds and published by John Wiley & Sons. This book was released on 1974 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:
