Download or read book Geometric Sensitivity of Three dimensional Separated Flows written by Erica Cherry and published by . This book was released on 2008 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sensitivity of Separated Flow in a Three dimensional Asymmetric Diffuser to Inlet Condition Perturbations written by Emily L. Sayles and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The sensitivity of separated flow in an asymmetric, three-dimensional diffuser to inlet condition perturbations is investigated using particle image velocimetry. The diffuser has a simple design, expanding from a rectangular cross-section at its inlet to a square cross-section at its outlet, with an area expansion ratio of 4.8. The bottom wall and one sidewall are angled outwards while the other two walls remain flat. In the baseline flow, a large and stable separation bubble forms in the corner between the two diverging walls and spreads across the more aggressively expanding bottom wall. The diffuser is fed by a long, rectangular duct which develops secondary flows in the corners. The diffuser flow has proven to be highly sensitive to the modification of these secondary flows. Dielectric barrier discharge plasma actuators and passive vortex generators are used to purposefully and systematically manipulate the secondary flows in the inlet channel. Changes to the flow are documented using static pressure measurements, magnetic resonance velocimetry, and particle image velocimetry. In pilot-scale experiments, spanwise-acting dielectric barrier discharge plasma actuators installed on the floor of the inlet channel are used to generate a wide range of perturbations. The effects of these perturbations are reflected in changes as large as +/-25% to the baseline pressure recovery of the diffuser. Two sets of passive vortex generators were fabricated as analogs of two continuously operated plasma actuator cases. Magnetic resonance velocimetry measurements of the vortex generator cases reveal significant changes to the separation bubble geometry. An improved pressure recovery is associated with a delayed onset of separation and an overall smaller separation bubble. The case which degrades the pressure recovery develops a completely different separation geometry as flow separates from the expanding sidewall. The separation bubble grows rapidly, preventing the main flow from decelerating efficiently. In order to study the plasma actuator cases in more detail, particle image velocity measurements were acquired in the High Reynolds Number Facility. Following actuator scaling efforts and operating parameter optimization, a pulsed forcing case which improves the diffuser's performance, and a continuous forcing case which degrades it were chosen for further study. PIV measurements were obtained in five streamwise-wall normal planes and two spanwise-wall normal planes for all three cases. The measurements focus on the first half of the diffuser, where the majority of the losses in pressure recovery occur. Spanwise-wall normal data show that both pulsed and continuous forcing cases generate four distinct longitudinal vortices which redistribute streamwise momentum in the diffuser's inlet. The larger and stronger vortices formed by continuous forcing sweep low momentum fluid from the bottom wall and deposit it along the sidewalls. The separation bubble for this case forms along the expanding sidewall instead of along the bottom wall as in the other two cases. The protrusion of the separation bubble into the diffuser from the sidewall creates a blockage of forward-moving flow, distorting velocity contours and keeping velocities high in the core of the diffuser. Elevated streamwise and vertical normal stresses distributed throughout the planes suggest that this separation bubble is unsteady. Pulsed forcing delays separation along the bottom wall by increasing turbulent activity in the attached boundary layer upstream of separation. A large peak in shear stress is observed in one of the planes close to the expanding sidewall. Elevated levels of normal stresses are observed for this case as well, but the distribution of these stresses and the overall flow structure closely resemble the baseline flow.
Download or read book Direct and Large Eddy Simulation VIII written by Hans Kuerten and published by Springer Science & Business Media. This book was released on 2011-10-05 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume continues previous DLES proceedings books, presenting modern developments in turbulent flow research. It is comprehensive in its coverage of numerical and modeling techniques for fluid mechanics. After Surrey in 1994, Grenoble in 1996, Cambridge in 1999, Enschede in 2001, Munich in 2003, Poitiers in 2005, and Trieste in 2009, the 8th workshop, DLES8, was held in Eindhoven, The Netherlands, again under the auspices of ERCOFTAC. Following the spirit of the series, the goal of this workshop is to establish a state-of-the-art of DNS and LES techniques for the computation and modeling of transitional/turbulent flows covering a broad scope of topics such as aerodynamics, acoustics, combustion, multiphase flows, environment, geophysics and bio-medical applications. This gathering of specialists in the field was a unique opportunity for discussions about the more recent advances in the prediction, understanding and control of turbulent flows in academic or industrial situations.
Download or read book Three dimensional Separated Flow Topology written by Jean Délery and published by John Wiley & Sons. This book was released on 2013-02-28 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book develops concepts and a methodology for a rational description of the organization of three-dimensional flows considering, in particular, the case where the flow is the place of separations. The descriptive analysis based on the critical point theory of Poincaré develops conventional but rather unfamiliar considerations from aerodynamicists, who face the understanding of complex flows including multiple separation lines and vortices. These problems concern industrial sectors where aerodynamics plays a key role, such as aerospace, ground vehicles, buildings, etc. Contents 1. Skin Friction Lines Pattern and Critical Points. 2. Separation Streamsurfaces and Vortex Structures. 3. Separated Flow on a Body. 4. Vortex Wake of Wings and Slender Bodies. 5. Separation Induced by an Obstacle or a Blunt Body. 6. Reconsideration of the Two-Dimensional Separation. 7. Concluding Remarks. About the Authors Jean Délery is a Supaero (French National Higher School of Aeronautics and Space) engineer who has worked at Onera (French national aerospace research center) since 1964. He has participated in several major French and European aerospace programs, is the author of many scientific publications, and has occupied various teaching positions particularly at Supaero, the University of Versailles-Saint-Quentin, Ecole polytechnique in France and “La Sapienza” University in Rome, Italy. He is currently emeritus adviser at Onera.
Download or read book Direct and Large Eddy Simulation XIII written by Cristian Marchioli and published by Springer Nature. This book was released on 2023-11-15 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the diverse and cutting-edge research presented at the 13th ERCOFTAC Workshop on Direct and Large Eddy Simulation. The first section of the book focuses on Aerodynamics/Aeroacoustics, comprising eight papers that delve into the intricate relationship between fluid flow and aerodynamic performance. The second section explores the dynamics of Bluff/Moving Bodies through four insightful papers. Bubbly Flows, the subject of the third section, is examined through four papers. Moving on, the fourth section is dedicated to Combustion and Reactive Flows, presenting two papers that focus on the complex dynamics of combustion processes and the interactions between fluids and reactive species. Convection and Heat/Mass Transfer are the central themes of the fifth section, which includes three papers. These contributions explore the fundamental aspects of heat and mass transfer in fluid flows, addressing topics such as convective heat transfer, natural convection, and mass transport phenomena. The sixth section covers Data Assimilation and Uncertainty Quantification, featuring two papers that highlight the importance of incorporating data into fluid dynamic models and quantifying uncertainties associated with these models. The subsequent sections encompass a wide range of topics, including Environmental and Industrial Applications, Flow Separation, LES Fundamentals and Modelling, Multiphase Flows, and Numerics and Methodology. These sections collectively present a total of 23 papers that explore different facets of fluid dynamics, contributing to the advancement of the field and its practical applications.
Download or read book Advances in Turbulence XII written by Bruno Eckhardt and published by Springer Science & Business Media. This book was released on 2010-03-17 with total page 973 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume comprises the communications presented at the EUROMECH European Turbulence Conference ETC12, held in Marburg in September 2009. The topics covered by the meeting include: Acoustics of turbulent flows, Atmospheric turbulence, Control of turbulent flows, Geophysical and astrophysical turbulence, Instability and transition, Intermittency and scaling, Large eddy simulation and related techniques, Lagrangian aspects, MHD turbulence, Reacting and compressible turbulence, Transport and mixing, Turbulence in multiphase and non-Newtonian flows, Vortex dynamics and structure, formation, Wall bounded flows.
Download or read book Flow and Combustion in Advanced Gas Turbine Combustors written by Johannes Janicka and published by Springer Science & Business Media. This book was released on 2012-10-29 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: With regard to both the environmental sustainability and operating efficiency demands, modern combustion research has to face two main objectives, the optimization of combustion efficiency and the reduction of pollutants. This book reports on the combustion research activities carried out within the Collaborative Research Center (SFB) 568 “Flow and Combustion in Future Gas Turbine Combustion Chambers” funded by the German Research Foundation (DFG). This aimed at designing a completely integrated modeling and numerical simulation of the occurring very complex, coupled and interacting physico-chemical processes, such as turbulent heat and mass transport, single or multi-phase flows phenomena, chemical reactions/combustion and radiation, able to support the development of advanced gas turbine chamber concepts
Download or read book Numerical Simulation of Turbulent Flows and Noise Generation written by Christophe Brun and published by Springer Science & Business Media. This book was released on 2009-03-07 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large Eddy Simulation (LES) is a high-fidelity approach to the numerical simulation of turbulent flows. Recent developments have shown LES to be able to predict aerodynamic noise generation and propagation as well as the turbulent flow, by means of either a hybrid or a direct approach. This book is based on the results of two French/German research groups working on LES simulations in complex geometries and noise generation in turbulent flows. The results provide insights into modern prediction approaches for turbulent flows and noise generation mechanisms as well as their use for novel noise reduction concepts.
Download or read book Progress in Hybrid RANS LES Modelling written by Song Fu and published by Springer Science & Business Media. This book was released on 2012-08-14 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present book contains contributions presented at the Fourth Symposium on Hybrid RANS-LES Methods, held in Beijing, China, 28-30 September 2011, being a continuation of symposia taking place in Stockholm (Sweden, 2005), in Corfu (Greece, 2007), and Gdansk (Poland, 2009). The contributions to the last two symposia were published as NNFM, Vol. 97 and Vol. 111. At the Beijing symposium, along with seven invited keynotes, another 46 papers (plus 5 posters) were presented addressing topics on Novel turbulence-resolving simulation and modelling, Improved hybrid RANS-LES methods, Comparative studies of difference modelling methods, Modelling-related numerical issues and Industrial applications.. The present book reflects recent activities and new progress made in the development and applications of hybrid RANS-LES methods in general.
Download or read book Progress in Hybrid RANS LES Modelling written by Yannick Hoarau and published by Springer. This book was released on 2018-03-09 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reports on the latest developments in computational fluid dynamics and turbulence modeling, with a special emphasis on hybrid RANS-LES methods and their industrial applications. It gathers the proceedings of the Sixth Symposium on Hybrid RANS-LES Methods, held on September 26-28 in Strasbourg, France. The different chapters covers a wealth of topics such as flow control, aero-acoustics, aero-elasticity and CFD-based multidisciplinary optimization. Further topics include wall-modelled Large Eddy Simulation (WMLES), embedded LES, Lattice-Bolzman methods, turbulence-resolving applications and comparisons between LES, hybrid RANS-LES and URANS methods. The book addresses academic researchers, graduate students, industrial engineers, as well as industrial R&D managers and consultants dealing with turbulence modelling, simulation and measurement, and with multidisciplinary applications of computational fluid dynamics.
Download or read book Modelling Turbulence in Engineering and the Environment written by Kemal Hanjalić and published by Cambridge University Press. This book was released on 2022-11-24 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modelling transport and mixing by turbulence in complex flows are huge challenges for computational fluid dynamics (CFD). This highly readable book introduces readers to modelling levels that respect the physical complexity of turbulent flows. It examines the hierarchy of Reynolds-averaged Navier-Stokes (RANS) closures in various situations ranging from fundamental flows to three-dimensional industrial and environmental applications. The general second-moment closure is simplified to linear eddy-viscosity models, demonstrating how to assess the applicability of simpler schemes and the conditions under which they give satisfactory predictions. The principal changes for the second edition reflect the impact of computing power: a new chapter devoted to unsteady RANS and another on how large-eddy simulation, LES, and RANS strategies can be effectively combined for particular applications. This book will remain the standard for those in industry and academia seeking expert guidance on the modelling options available, and for graduate students in physics, applied mathematics and engineering entering the world of turbulent flow CFD.
Download or read book Topology of Three dimensional Separated Flows written by M. Tobak and published by . This book was released on 1981 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Progress in Wall Turbulence 2 written by Michel Stanislas and published by Springer. This book was released on 2015-08-17 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the proceedings of the ERCOFTAC Workshop on Progress in Wall Turbulence: Understanding and Modelling, that was held in Lille, France from June 18 to 20, 2014. The workshop brought together world specialists of near wall turbulence and stimulated exchanges between them around up-to-date theories, experiments, simulations and numerical models. This book contains a coherent collection of recent results on near wall turbulence including theory, new experiments, DNS and modeling with RANS, LES. The fact that both physical understanding and modeling by different approaches are addressed by the best specialists in a single workshop is original.
Download or read book Three Dimensional Flows written by Vítor Araújo and published by Springer Science & Business Media. This book was released on 2010-06-10 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, the authors present the elements of a general theory for flows on three-dimensional compact boundaryless manifolds, encompassing flows with equilibria accumulated by regular orbits. The book aims to provide a global perspective of this theory and make it easier for the reader to digest the growing literature on this subject. This is not the first book on the subject of dynamical systems, but there are distinct aspects which together make this book unique. Firstly, this book treats mostly continuous time dynamical systems, instead of its discrete counterpart, exhaustively treated in some other texts. Secondly, this book treats all the subjects from a mathematical perspective with proofs of most of the results included. Thirdly, this book is meant to be an advanced graduate textbook and not just a reference book or monograph on the subject. This aspect is reflected in the way the cover material is presented, with careful and complete proofs, and precise references to topics in the book.
Download or read book Geometric Sensitivity Wake Dynamics and Machine Learning Turbulence Modeling on a Skewed Bump written by David Sunghwa Ching and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A flow is considered geometrically sensitive if a slight perturbation to the geometry results in a major change to the flow structure. This work examines the flow over a wall-mounted, skewed bump, which exhibits geometric sensitivity. The bump is three-dimensional and has elliptical cross-sections with axis ratio of 4/3, and the geometry is modified by placing the bump at different angles with respect to the freestream. A combined experimental and computational approach is used to study the bump flow. The distinguishing features are a large separation bubble and longitudinal vortex structures in the wake. The wake has a quasi-periodic shedding cycle that is examined with Spectral Proper Orthogonal Decomposition (SPOD) and conditional averaging. Experiments are done to examine how the flow changes when the bump surface is rough. Reynolds Averaged Navier-Stokes (RANS) simulations have poor accuracy in this flow, and a method is developed to improve RANS accuracy using machine learning.
Download or read book Computation of Navier Stokes Equations for Three dimensional Flow Separation written by and published by . This book was released on 1989 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Separated Flow and Boundary Layer Research written by Seymour M. Bogdonoff and published by . This book was released on 1980 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: The two-dimensional corner study provides a unique framework bridging attached to separated flows. It only needs the measurements of local heat transfer and flowfield fluctuating measurements to be a complete description of an important shock wave boundary layer configuration. The study of a two-dimensional reattaching free shear layer has provided a unique series of measurements, including the first turbulence data, at one flow condition and geometry. Reynolds number and geometry effects have yet to be studied, but the physics of reattachment have been explored in a way not heretofore examined. The investigation of three-dimensional shock wave turbulent boundary layer interactions, specifically of the swept wedge, provides new insights into these complex flows with strong lateral gradients. The studies have revealed many new elements, but 'separation' and 'reattachment' take on new meanings which have yet to be clarified. Hypersonic turbulent boundary layers have been found to have very complex structures with very wide density variations and orders of magnitude unit Reynolds number changes across the layers. Highly viscous, laminar sublayers, are bounded by turbulent layers in which fluctuations of 50% are experienced. Many of the results of the present studies were used to test, validate, and guide major efforts in computational fluid dynamics. To date, the computations adequately describe attached flows, but do not capture the details of separated flows, although general characteristics of the flow field are predicted. The results of computations, sensitivity analysis, and testing of various models (turbulence) were important guides for the experimental studies.
