Download or read book Direct Numerical Simulation of Laminar and Turbulent Rayleigh B nard Convection written by Firas Dabbagh and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The main aim of this work is understanding the phenomenon of B enard cells in laminar and turbulent regimes as an application of studying the air flow in the air gap and honey comb cells that installed in the flat plate solar collector. Furthermore analyzing the turbulent Rayleigh-B enard convection components by performing direct numerical simulation of turbulent air ow in too long inclined cavity like the air gap. The fi rst two chapters treat with known problems of laminar and turbulent flow as a necessary presentation of numerical methods used in solving the governing equation of flow motion and heat transfer, afterward the third chapter deals with the main object of investigating the turbulent and laminar Rayleigh-B enard convection flow.

Download or read book Turbulence and Interactions written by Michel O. Deville and published by Springer. This book was released on 2014-06-13 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents a snapshot of the state-of-art in the field of turbulence modeling and covers the latest developments concerning direct numerical simulations, large eddy simulations, compressible turbulence, coherent structures, two-phase flow simulation and other related topics. It provides readers with a comprehensive review of both theory and applications, describing in detail the authors’ own experimental results. The book is based on the proceedings of the third Turbulence and Interactions Conference (TI 2012), which was held on June 11-14 in La Saline-les-Bains, La Réunion, France and includes both keynote lectures and outstanding contributed papers presented at the conference. This multifaceted collection, which reflects the conference ́s emphasis on the interplay of theory, experiments and computing in the process of understanding and predicting the physics of complex flows and solving related engineering problems, offers a practice-oriented guide for students, researchers and professionals in the field of computational fluid dynamics, turbulence modeling and related areas.

Download or read book Direct Numerical Simulations of Turbulent Rayleigh B nard Convection written by Wei Xu and published by . This book was released on 2020 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Numerical Simulation of Laminar and Turbulent Flow in a Channel with Complex Time dependent Wall Geometries written by Henry Andrew Carlson and published by . This book was released on 1995 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Direct Numerical Simulation of Laminar and Turbulent Flow Over Streamwise Aligned Riblets written by Douglas C. Chu and published by . This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Numerical Simulation of Laminar and Turbulent Flows in a Diverging Channel written by K. Dang Tran and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineering Turbulence Modelling and Experiments 5 written by W. Rodi and published by Elsevier. This book was released on 2002-08-21 with total page 1029 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence is 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 increasingly on the performance of the turbulence models. This series of symposia provides a forum for presenting and discussing new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. The papers in this set of proceedings were presented at the 5th International Symposium on Engineering Turbulence Modelling and Measurements in September 2002. They look at a variety of areas, including: Turbulence modelling; Direct and large-eddy simulations; Applications of turbulence models; Experimental studies; Transition; Turbulence control; Aerodynamic flow; Aero-acoustics; Turbomachinery flows; Heat transfer; Combustion systems; Two-phase flows. These papers are preceded by a section containing 6 invited papers covering various aspects of turbulence modelling and simulation as well as their practical application, combustion modelling and particle-image velocimetry.

Download or read book Internally Heated Convection and Rayleigh B nard Convection written by David Goluskin and published by Springer. This book was released on 2015-11-21 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief describes six basic models of buoyancy-driven convection in a fluid layer: three configurations of internally heated convection and three configurations of Rayleigh-Bénard convection. The author discusses the main quantities that characterize heat transport in each model, along with the constraints on these quantities. This presentation is the first to place the various models in a unified framework, and similarities and differences between the cases are highlighted. Necessary and sufficient conditions for convective motion are given. For the internally heated cases only, parameter-dependent lower bounds on the mean fluid temperature are proven, and results of past simulations and laboratory experiments are summarized and reanalyzed. The author poses several open questions for future study.

Download or read book Flow Topology and Small scale Dynamics in Turbulent Rayleigh B nard Convection written by Firas Dabbagh and published by . This book was released on 2017 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Without fluid turbulence, life might have rather different look. The atmosphere and oceans could nearly maintain a much larger temperature differences resulting in ultimate heating or cooling to the earth surface. The water and air flow could rather run much faster at rates of the speed of sound. Turbulence is a highly active nature of chaotic, random and three-dimensionality of swirling fluid. Its nonlinear convective property transports the momentum and energy in a helical mechanism leading eventually to an enriched fluid mixing and generating of small scale motions. These scales chiefly rule the hairpin vorticity dynamics, the strain production and the cascade of kinetic energy mechanisms. Hence, the key feature in turbulence is around disclosing the small scale motions. Studying the fine-scale dynamics gives us fundamental perspectives of flow topology and thus, improves our knowledge of turbulence physics. The turbulence dynamo becomes more complex when the active thermal gradient constitutes into the pure generator of turbulence. This particularly happens in the so-called buoyancy-driven Rayleigh-Bénard convection (RBC), when an infinite/bounded lying fluid is heated from below and cooled from above in the field of gravity. The main goal of this thesis is investigating the flow topology and small-scale dynamics in turbulent RBC, in order to better understanding its thermal turbulence mechanism and improve/validate the turbulence modeling for the foreseeable Computational-Fluid-Dynamics future. To do so, a complete direct numerical simulation (DNS) of turbulent RBC in a rectangular air-filled cavity of aspect ratio unity and pi spanwise open-ended distance, has been presented at Rayleigh numbers Ra={1e8, 1e10}, in chapter 1. A global kinetic energy conservation is inherited using a fourth-order symmetry-preserving scheme for the spatial discretization, and the flow dynamics is explored by analysis of kinetic and thermal energy power spectra, probability density function (PDF) of viscous and thermal dissipation rates, and identification of the wind in RBC. In chapter 2, the DNS dataset is used to investigate several universal small-scale features observed in various turbulent flows and recaptured here in turbulent RBC through the bulk. For instance, the inclined "teardrop" shape of joint PDF velocity gradient tensor invariants (Q,R), the preferential alignment of vorticity with the intermediate eigenstrain vector, and the spiraling degenerated behavior of the average rates invariants (DQ/Dt,DR/Dt). It is found that a self-amplification of viscous straining -Qs results at Ra=1e10, helps in contracting the vorticity worms and enhances slightly the linear contributions of the vortex stretching mechanism. On the other hand, the evolution of relevant small-scale thermals has been addressed by investigating the average rate of invariants pertained to the traceless part of velocity-times-temperature gradient tensor i.e., (DQt/Dt,DRt/Dt). The new invariants are shown to follow correctly the evolution and lifetime of thermal plumes in RBC and hence disclose interactions of buoyant production and viscous dissipation. In chapter 3, the DNS dataset is employed to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent RBC in the spirit of Large-eddy simulation (LES) turbulence modeling. To do so, the key ingredients of eddy-viscosity, eddy-diffusivity and turbulent Prandtl number, are calculated a priori and investigated in a topological point-of-view. As a result, it has been suggested the restricted application of the hypothesis of a constant turbulent Prandtl number only in the large-scale strain-dominated areas. More arguments have been attained through a priori investigation of the alignment trends imposed by existing parameterizations for the SGS heat flux. Finally, a new tensorial approach of modeling the SGS of thermal turbulence is sought, that opens new research trends in the future.

Download or read book Advanced Turbulent Flow Computations written by Roger Peyret and published by Springer. This book was released on 2014-05-04 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects the lecture notes concerning the IUTAM School on Advanced Turbulent Flow Computations held at CISM in Udine September 7–11, 1998. The course was intended for scientists, engineers and post-graduate students interested in the application of advanced numerical techniques for simulating turbulent flows. The topic comprises two closely connected main subjects: modelling and computation, mesh pionts necessary to simulate complex turbulent flow.

Download or read book Direct Numerical Simulation of Ablative Boundaries in Turbulent and Laminar Flows written by Ryan Campbell Crocker and published by . This book was released on 2015 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid surface ablation by a turbulent flow creates complex flow and surface phenomena arising from the evolving boundary topography and its interaction with a turbulent flow that transports the ablative agent onto the surface. The dynamic nature of ablative flow boundaries generate unsteady flow dynamics and thermodynamics occurring over a wide range of scales. The non-equilibrium nature of these phenomena pose a major challenge to the current fundamental understanding of turbulence, which is mostly derived from equilibrium flows, and to Computational Fluid Dynamics (CFD). The simulation of moving boundaries is a necessary tradeoff between computational speed and accuracy. The most accurate methods use surface-conforming grids, forcing the grid to move and deform in time at a high computational cost. The technique used in this study, immersed boundary methods, removes the need for a surface-conforming grid, typically at the expense of numerical accuracy. The objectives of the present study are (i) to develop an Energy Immersed Boundary Method (EIBM) to simulate conjugate heat transfer and phase change with a spatial order of accuracy larger than one, and (ii) use the EIBM to study the dynamics of ablative flows. A generalized finite volume (FV) flow solver with second-order accuracy in time and space and energy conserving schemes is the basis of the EIBM algorithm development. The EIBM com- bines level-set method for the definition and transport of the fluid/solid interface with an immersed boundary method, i.e. a modification of the transport equation to enforce the proper boundary conditions at the solid surface. The proposed algorithm is shown to be second order accurate in space in the simulation of conjugate heat transfer flows. The validation also included comparison with phase-change (melting) experiments where it was shown to correlate very well to previous ex- periments of a rectangular slab of gallium melted from one side. As well as showing second order convergence for the mass loss and the ablated shape of a cylinder in a melting cross flow. The EIBM is applied to an investigation of the interactions between turbulence and an erodible surface. The study first focuses on the response of a turbulent flow over a receding wall, with constant recession velocity. It is found that wall recession velocities, near the small scale, the Kolmorgorov microscale, velocity of the buffer layer, produce minute shear free layers near the wall which both enhanced and stretched out the low and high velocity streaks near the wall. The larger streak area produced larger turbulent intensities on the dynamic boundary side of the channel, and far more semi-streamwise vortices. In the Second study the EIBM is applied to the ablation of a generic slab in a turbulent channel heated from one side in the absence of gravity. The study focuses on the characterization of the surface topography in relation to the evolution of coherent structures in the flow as ablation proceeds. The produced surface topology is linked to the flow topology and the turbulent generating and dissipating forces inside the turbulent flow. It is shown that the streaks for stefan numbers producing average ablation velocities slightly smaller than the Kolmorgorov microscale create groves in which the high speed buffer layer streaks sit, and their sinus motion in the spanwise direction is reduced.

Download or read book Numerical Modeling of Turbulent Convection in Rough Rayleigh B nard Cell written by Mebarek Belkadi and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent convective flows over rough boundaries are ubiquitous in geophysical and engineering applications. Understanding the mechanisms of these interactions is substantial for improving the heat transfer efficiency. In this work we study the effects of wall roughness on the Rayleigh Bénard turbulence. Three dimensional direct numerical simulations (DNS) are performed using a parallel CFD code under the support of national high performance computers. The roughness elements are embedded over hotted surface using an immersed boundary method. The numerical configuration allow the identification of three successive regimes from a thermally resistant to highly enhanced heat transfer. Through a geometrical decomposition of the rough plate into plot and surrounding fluid, we examine their different behaviors, mainly the contribution to the heat transfer. We analyze the effects of roughness on thermal and viscous boundary layers structures and on the flow physics near the wall. Besides that, the comparison with experimental data at the roughness scale highlight the non homogeneity of thermal fluctuations around the obstacles. We also focused on the effects of roughness on the flow dynamics and on the properties of thermal plumes.

Download or read book Numerical Methods in Turbulence Simulation written by Robert Moser and published by Elsevier. This book was released on 2022-11-30 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical Methods in Turbulence Simulation provides detailed specifications of the numerical methods needed to solve important problems in turbulence simulation. Numerical simulation of turbulent fluid flows is challenging because of the range of space and time scales that must be represented. This book provides explanations of the numerical error and stability characteristics of numerical techniques, along with treatments of the additional numerical challenges that arise in large eddy simulations. Chapters are written as tutorials by experts in the field, covering specific both contexts and applications. Three classes of turbulent flow are addressed, including incompressible, compressible and reactive, with a wide range of the best numerical practices covered. A thorough introduction to the numerical methods is provided for those without a background in turbulence, as is everything needed for a thorough understanding of the fundamental equations. The small scales that must be resolved are generally not localized around some distinct small-scale feature, but instead are distributed throughout a volume. These characteristics put particular strain on the numerical methods used to simulate turbulent flows. - Includes a detailed review of the numerical approximation issues that impact the simulation of turbulence - Provides a range of examples of large eddy simulation techniques - Discusses the challenges posed by boundary conditions in turbulence simulation and provides approaches to addressing them

Download or read book Modeling and Simulation of Turbulent Flows written by Roland Schiestel and published by John Wiley & Sons. This book was released on 2010-01-05 with total page 751 pages. Available in PDF, EPUB and Kindle. Book excerpt: This title provides the fundamental bases for developing turbulence models on rational grounds. The main different methods of approach are considered, ranging from statistical modelling at various degrees of complexity to numerical simulations of turbulence. Each of these various methods has its own specific performances and limitations, which appear to be complementary rather than competitive. After a discussion of the basic concepts, mathematical tools and methods for closure, the book considers second order closure models. Emphasis is placed upon this approach because it embodies potentials for clarifying numerous problems in turbulent shear flows. Simpler, generally older models are then presented as simplified versions of the more general second order models. The influence of extra physical parameters is also considered. Finally, the book concludes by examining large Eddy numerical simulations methods. Given the book’s comprehensive coverage, those involved in the theoretical or practical study of turbulence problems in fluids will find this a useful and informative read.

Download or read book Modeling and Simulation of Turbulent Mixing and Reaction written by Daniel Livescu and published by Springer Nature. This book was released on 2020-02-19 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights recent research advances in the area of turbulent flows from both industry and academia for applications in the area of Aerospace and Mechanical engineering. Contributions include modeling, simulations and experiments meant for researchers, professionals and students in the area.

Download or read book New Tools in Turbulence Modelling written by Olivier Metais and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical large-eddy simulation techniques are booming at present and will have a decisive impact on industrial modeling and flow control. The book represents the general framework in physical and spectral space. It also gives the recent subgrid-scale models. Topics treated include compressible turbulence research, turbulent combustion, acoustic predictions, vortex dynamics in non-trivial geometries, flows in nuclear reactors and problems in atmospheric and geophysical sciences. The book addresses numerical analysts, physicists, and engineers.

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.