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Toward Understanding And Modeling Compressibility Effects On Velocity Gradients In Turbulence
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Book Synopsis Toward Understanding and Modeling Compressibility Effects on Velocity Gradients in Turbulence by : Sawan Suman
Download or read book Toward Understanding and Modeling Compressibility Effects on Velocity Gradients in Turbulence written by Sawan Suman and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of improved turbulence closure models for compressible fluid flow simulations requires better understanding of the effects of compressibility on various underlying processes of turbulence. Fundamental studies of turbulent velocity gradients hold the key to understanding several non-linear processes like material element deformation, energy cascading, intermittency and mixing. Experiments, direct numerical simulation (DNS) and simple mathematical models are three approaches to study velocity gradients. With the goal of furthering our understanding of the effects of compressibility on turbulent velocity gradients, this dissertation (i) employs DNS results to characterize some of the effects of compressibility on turbulent velocity gradients, and (ii) develops simple mathematical models for velocity gradient dynamics in compressible turbulence. In the first part of the dissertation, effects of compressibility on velocity gradient invariants and the local topology of compressible turbulence are characterized employing DNS results of compressible decaying isotropic turbulence. Joint statistics of second and third invariants of velocity gradient tensor and the exact probability of occurrence of associated topologies conditioned upon dilatation (degree of compression/expansion of fluid) are computed. These statistics are found to be (i) highly dependent on dilatation and (ii) substantially different from the statistics observed in incompressible turbulence. These dilatation-conditioned statistics of compressible turbulence, however, are found to be fairly independent of Mach number and Reynolds number. In the second part of the dissertation, two mathematical models for compressible velocity gradient dynamics are developed. To take into account the significant aero-thermodynamic coupling that exists in compressible flows, the models are derived explicitly using the continuity, energy and state equations, along with the momentum equation. The modeling challenge involved in the development of these models lies in capturing the inherently non-local nature of pressure and viscous effects as a function of local terms to derive a closed set of ordinary differential equations. The models developed in this dissertation are evaluated in a variety of flow regimes - incompressible limit (low Mach number); pressure-released limit (extremely high Mach number); and intermediate (sub-sonic Mach numbers) - and are shown to recover a range of known compressibility effects.
Book Synopsis Compressibility, Turbulence and High Speed Flow by : Thomas B. Gatski
Download or read book Compressibility, Turbulence and High Speed Flow written by Thomas B. Gatski and published by Elsevier. This book was released on 2009-02-27 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. For the computation of turbulent compressible flows, current methods of averaging and filtering are presented so that the reader is exposed to a consistent development of applicable equation sets for both the mean or resolved fields as well as the transport equations for the turbulent stress field. For the measurement of turbulent compressible flows, current techniques ranging from hot-wire anemometry to PIV are evaluated and limitations assessed. Characterizing dynamic features of free shear flows, including jets, mixing layers and wakes, and wall-bounded flows, including shock-turbulence and shock boundary-layer interactions, obtained from computations, experiments and simulations are discussed. Describes prediction methodologies including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) Presents current measurement and data analysis techniques Discusses the linkage between experimental and computational results necessary for validation of numerical predictions Meshes the varied results of computational and experimental studies in both free and wall-bounded flows to provide an overall current view of the field
Download or read book Turbulent Flows written by Jean Piquet and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 767 pages. Available in PDF, EPUB and Kindle. Book excerpt: obtained are still severely limited to low Reynolds numbers (about only one decade better than direct numerical simulations), and the interpretation of such calculations for complex, curved geometries is still unclear. It is evident that a lot of work (and a very significant increase in available computing power) is required before such methods can be adopted in daily's engineering practice. I hope to l"Cport on all these topics in a near future. The book is divided into six chapters, each· chapter in subchapters, sections and subsections. The first part is introduced by Chapter 1 which summarizes the equations of fluid mechanies, it is developed in C~apters 2 to 4 devoted to the construction of turbulence models. What has been called "engineering methods" is considered in Chapter 2 where the Reynolds averaged equations al"C established and the closure problem studied (§1-3). A first detailed study of homogeneous turbulent flows follows (§4). It includes a review of available experimental data and their modeling. The eddy viscosity concept is analyzed in §5 with the l"Csulting ~alar-transport equation models such as the famous K-e model. Reynolds stl"Css models (Chapter 4) require a preliminary consideration of two-point turbulence concepts which are developed in Chapter 3 devoted to homogeneous turbulence. We review the two-point moments of velocity fields and their spectral transforms (§ 1), their general dynamics (§2) with the particular case of homogeneous, isotropie turbulence (§3) whel"C the so-called Kolmogorov's assumptions are discussed at length.
Book Synopsis Quantitative Analysis of Geopressure for Geoscientists and Engineers by : Nader C. Dutta
Download or read book Quantitative Analysis of Geopressure for Geoscientists and Engineers written by Nader C. Dutta and published by Cambridge University Press. This book was released on 2021-03-11 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of the processes related to geopressure development, prediction and detection using state-of-the-art tools and technologies.
Book Synopsis Engineering Turbulence Modelling and Experiments - 4 by : D. Laurence
Download or read book Engineering Turbulence Modelling and Experiments - 4 written by D. Laurence and published by Elsevier. This book was released on 1999-04-14 with total page 975 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings contain the papers presented at the 4th International Symposium on Engineering Turbulence Modelling and Measurements held at Ajaccio, Corsica, France from 24-26 May 1999. It follows three previous conferences on the topic of engineering turbulence modelling and measurements. The purpose of this series of symposia is to provide a forum for presenting and discussing new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. Turbulence is still one of the key issues in tackling engineering flow problems. As powerful computers and accurate numerical methods are now available for solving the flow equations, and since engineering applications nearly always involve turbulence effects, the reliability of CFD analysis depends more and more on the performance of the turbulence models. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation.
Book Synopsis Modeling Complex Turbulent Flows by : Manuel D. Salas
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.
Book Synopsis Effect of Compressibility on the Turbulence Structure and Its Modeling by :
Download or read book Effect of Compressibility on the Turbulence Structure and Its Modeling written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study, the compressibility effect is investigated in the context of the two-equation k-epsilon model. Several models have been proposed to deal with the dissipative nature of compressibility and the complexities arising due to the non-divergent nature of the velocity field. In addition modifications have been proposed to address the added time-scale effect that is due to a non-equlibrium between the rates of production and dissipation of turbulent kinetic energy in complex flows. The reduced dependence, of the k-omega based models on the spatial gradients in density, has been shown to be an artifact of the neglect of cross-diffusion terms in the transport equation for omega. Through a systematic study of the exact form of the turbulence transport equations two additional source terms that are unique to compressible turbulent flows, namely the enthalpic production term and the term representing the baroclinic effect, have been identified and models are proposed.
Book Synopsis Homogeneous Turbulence Dynamics by : Pierre Sagaut
Download or read book Homogeneous Turbulence Dynamics written by Pierre Sagaut and published by Springer. This book was released on 2018-03-23 with total page 912 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides state-of-the-art results and theories in homogeneous turbulence, including anisotropy and compressibility effects with extension to quantum turbulence, magneto-hydodynamic turbulence and turbulence in non-newtonian fluids. Each chapter is devoted to a given type of interaction (strain, rotation, shear, etc.), and presents and compares experimental data, numerical results, analysis of the Reynolds stress budget equations and advanced multipoint spectral theories. The role of both linear and non-linear mechanisms is emphasized. The link between the statistical properties and the dynamics of coherent structures is also addressed. Despite its restriction to homogeneous turbulence, the book is of interest to all people working in turbulence, since the basic physical mechanisms which are present in all turbulent flows are explained. The reader will find a unified presentation of the results and a clear presentation of existing controversies. Special attention is given to bridge the results obtained in different research communities. Mathematical tools and advanced physical models are detailed in dedicated chapters.
Book Synopsis Progress in Turbulence Modeling for Complex Flow Fields Including Effects of Compressibility by : David C. Wilcox
Download or read book Progress in Turbulence Modeling for Complex Flow Fields Including Effects of Compressibility written by David C. Wilcox and published by . This book was released on 1980 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Adm Nasa Publisher :Independently Published ISBN 13 :9781792954474 Total Pages :28 pages Book Rating :4.9/5 (544 download)
Book Synopsis Turbulence Modeling for High Speed Compressible Flows by : National Aeronautics and Space Adm Nasa
Download or read book Turbulence Modeling for High Speed Compressible Flows written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-04 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following grant objectives were delineated in the proposal to NASA: to offer course work in computational fluid dynamics (CFD) and related areas to enable mechanical engineering students at North Carolina A&T State University (N.C. A&TSU) to pursue M.S. studies in CFD, and to enable students and faculty to engage in research in high speed compressible flows. Since no CFD-related activity existed at N.C. A&TSU before the start of the NASA grant period, training of students in the CFD area and initiation of research in high speed compressible flows were proposed as the key aspects of the project. To that end, graduate level courses in CFD, boundary layer theory, and fluid dynamics were offered. This effort included initiating a CFD course for graduate students. Also, research work was performed on studying compressibility effects in high speed flows. Specifically, a modified compressible dissipation model, which included a fourth order turbulent Mach number term, was incorporated into the SPARK code and verified for the air-air mixing layer case. The results obtained for this case were compared with a wide variety of experimental data to discern the trends in the mixing layer growth rates with varying convective Mach numbers. Comparison of the predictions of the study with the results of several analytical models was also carried out. The details of the research study are described in the publication entitled 'Compressibility Effects in Modeling Turbulent High Speed Mixing Layers, ' which is attached to this report. Chandra, Suresh NASA-CR-194547, NAS 1.26:194547 NAG1-1287...
Download or read book Turbulent Flows written by G. Biswas and published by Narosa Publishing House. This book was released on 2002 with total page 476 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.
Book Synopsis Turbulence Models and Their Application by : Tuncer Cebeci
Download or read book Turbulence Models and Their Application written by Tuncer Cebeci and published by Springer Science & Business Media. This book was released on 2003-12-04 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: After a brief review of the more popular turbulence models, the author presents and discusses accurate and efficient numerical methods for solving the boundary-layer equations with turbulence models based on algebraic formulas (mixing length, eddy viscosity) or partial-differential transport equations. A computer program employing the Cebeci-Smith model and the k-e model for obtaining the solution of two-dimensional incompressible turbulent flows without separation is discussed in detail and is presented in the accompanying CD.
Book Synopsis Computation and Comparison of Efficient Turbulence Models for Aeronautics — European Research Project ETMA by : Alain Dervieux
Download or read book Computation and Comparison of Efficient Turbulence Models for Aeronautics — European Research Project ETMA written by Alain Dervieux and published by Springer Science & Business Media. This book was released on 1998-08-27 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains contributions to the BRITE-EURAM 3rd Framework Programme ETMA and extended articles of the TMA-Workshop. It focusses on turbulence modelling techniques suitable to use in typical flow configurations, with emphasis on compressibility effects and inherent unsteadiness. These methodologies are applied to the Navier-Stokes equations, involving various turbulence modelling levels from algebraic to RSM. Basic turbulent flows in aeronautics are considered; mixing layers, wall-flows (flat-plate, backward-facing step, ramp, bump), and more complex configurations (bump, aerofoil). A critical assessment of the turbulence modelling performances is offered, based on previous results and on the experimental data-base of this research programme. The ETMA results figure in the data-base constituted by all partners and organized by INRIA
Book Synopsis Turbulence Modelling Approaches by : Konstantin Volkov
Download or read book Turbulence Modelling Approaches written by Konstantin Volkov and published by BoD – Books on Demand. This book was released on 2017-07-26 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate prediction of turbulent flows remains a challenging task despite considerable work in this area and the acceptance of CFD as a design tool. The quality of the CFD calculations of the flows in engineering applications strongly depends on the proper prediction of turbulence phenomena. Investigations of flow instability, heat transfer, skin friction, secondary flows, flow separation, and reattachment effects demand a reliable modelling and simulation of the turbulence, reliable methods, accurate programming, and robust working practices. The current scientific status of simulation of turbulent flows as well as some advances in computational techniques and practical applications of turbulence research is reviewed and considered in the book.
Book Synopsis Analysis of Weakly Compressible Turbulence Using Symmetry Methods and Direct Numerical Simulation by : Raphael Gotthard Harald Arlitt
Download or read book Analysis of Weakly Compressible Turbulence Using Symmetry Methods and Direct Numerical Simulation written by Raphael Gotthard Harald Arlitt and published by Cuvillier Verlag. This book was released on 2005 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Multiple-scale Turbulence Modeling of Boundary Layer Flows for Scramjet Applications by : G. Fabris
Download or read book Multiple-scale Turbulence Modeling of Boundary Layer Flows for Scramjet Applications written by G. Fabris and published by . This book was released on 1981 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studying Turbulence Using Numerical Simulation Databases by : Center for Turbulence Research (U.S.)
Download or read book Studying Turbulence Using Numerical Simulation Databases written by Center for Turbulence Research (U.S.) and published by . This book was released on 1987 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
