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Author: Joon Sang Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 144
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Book Description
Structured grid finite volume formulations have been developed to solve the compressible Navier-Stokes equations for performing large eddy simulation of turbulent flows. These compressible formulations were developed using low Mach number preconditioning. Time marching was done with a coupled strongly implicit scheme. The discretization schemes were second-order accurate central difference and third-order accurate upwind and a comparison was made between two schemes. Validations were performed using turbulent compressible benchmark flows with low heat transfer. The results were compared to direct numerical simulation, experimental, and other large eddy simulation results. The large eddy simulations yielded excellent agreement with the direct numerical simulation and experimental results for incompressible turbulence. For the significant property variations, high heat transfer rate was imposed and the effects of buoyancy on the turbulent structures under stably, and unstably stratified flows were investigated. The effects of buoyancy were larger in the central region of channel where the largest Richardson number occurred. Despite the fact that the relative buoyancy production was small near the boundary walls, effects of buoyancy were observed.
Author: Joon Sang Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 144
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Book Description
Structured grid finite volume formulations have been developed to solve the compressible Navier-Stokes equations for performing large eddy simulation of turbulent flows. These compressible formulations were developed using low Mach number preconditioning. Time marching was done with a coupled strongly implicit scheme. The discretization schemes were second-order accurate central difference and third-order accurate upwind and a comparison was made between two schemes. Validations were performed using turbulent compressible benchmark flows with low heat transfer. The results were compared to direct numerical simulation, experimental, and other large eddy simulation results. The large eddy simulations yielded excellent agreement with the direct numerical simulation and experimental results for incompressible turbulence. For the significant property variations, high heat transfer rate was imposed and the effects of buoyancy on the turbulent structures under stably, and unstably stratified flows were investigated. The effects of buoyancy were larger in the central region of channel where the largest Richardson number occurred. Despite the fact that the relative buoyancy production was small near the boundary walls, effects of buoyancy were observed.
Author: Joon-Sang Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Joon Sang Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 262
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Book Description
The compressible filtered Navier-Stokes equations were solved using a second order accurate finite volume method with low Mach number preconditioning. A dynamic subgrid-scale stress model accounted for the subgrid-scale turbulence. The study focused on the effects of buoyancy and rotation on the structure of turbulence and transport processes including heat transfer. Several different physical arrangements were studied as outlined below. The effects of buoyancy were first studied in a vertical channel using large eddy simulation (LES). The walls were maintained at constant temperatures, one heated and the other cooled. Results showed that aiding and opposing buoyancy forces emerge near the heated and cooled walls, respectively. In the aiding flow, the turbulent intensities and heat transfer were suppressed at large values of Grashof number. In the opposing flow, however, turbulence was enhanced with increased velocity fluctuations. Another buoyancy study considered turbulent flow in a vertically oriented annulus. Isoflux wall boundary conditions with low and high heating were imposed on the inner wall while the outer wall was adiabatic. The results showed that the strong heating and buoyancy force caused distortions of the flow structure resulting in reduction of turbulent intensities, shear stress, and turbulent heat flux, particularly near the heated wall. Flow in an annular pipe with and without an outer wall rotation about its axis was first investigated at moderate Reynolds numbers. When the outer pipe wall was rotated, a significant reduction of turbulent kinetic energy was realized near the rotating wall. Secondly, a large eddy simulation has been performed to investigate the effect of swirl on the heat and momentum transfer in an annular pipe flow with a rotating inner wall. The simulations indicated that the Nusselt number and the wall friction coefficient increased with increasing rotation speed of the wall. It was also observed that the axial velocity profile became flattened and turbulent intensities were enhanced due to swirl. As a part of the study of rotation effects, a large eddy simulation of a rotating ribbed channel flow with the heat transfer was investigated. The rotation axis was parallel to the spanwise direction of the parallel plate channel. Uniform heat flux was applied to the channel for two rates of rotation. The results showed that near the stable (leading) side, the turbulent intensities and heat transfer were suppressed, but turbulence was enhanced with increasing shear stress and turbulent kinetic energy near the unstable (trailing) side.
Author: NA Schumann
Publisher: Springer Science & Business Media
ISBN: 3663001970
Category : Technology & Engineering
Languages : en
Pages : 350
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Book Description
This volume contains papers presented to a EUROMECH-Colloquium held in Munich, September 30 to October 2, 1985. The Colloquium is number 199 in a series of colloquia inaugurated by the European Mechanics Committee. The meeting was jointly organized by the 'Lehrstuhl fur Stromungsmechanik' at the 'Technische Universitat Munchen' and the 'Institut fur Physik der Atmosphare' of the 'Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt' (DFVLR) in Oberpfaffenhofen. 'Direct' and 'large eddy simulation' are terms which denote two closely con nected methods of turbulence research. In a 'direct simulation' (DS), turbu lent motion is simulated by numerically integrating the Navier-Stokes equations in three-dimensional space and as a function of time. Besides ini tial and boundary conditions no physical simplifications are involved. Com puter resources limit the resolution in time and space, though simulations with an order of one million discrete points in space are feasible. The simu lated flow fields can be considered as true realizations of turbulent flow fields and analysed to answer questions on the basic behaviour of turbulence. Direct simulations are valid as long as all the excited scales remain within the band of resolved scales. This means that viscosity must be strong enough to damp out the not resolved scales or the simulation is restricted to a lim ited integration-time interval only. In summary, DS provides a tool to investigate turbulent motions from first principles at least for a finite band of scales.
Author: Cristian Marchioli
Publisher: Springer Nature
ISBN: 3031470281
Category : Technology & Engineering
Languages : en
Pages : 389
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Book Description
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.
Author: Luigi Carlo Berselli
Publisher: Springer Science & Business Media
ISBN: 9783540263166
Category : Computers
Languages : en
Pages : 378
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Book Description
The LES-method is rapidly developing in many practical applications in engineering The mathematical background is presented here for the first time in book form by one of the leaders in the field
Author: M. Lesieur
Publisher: Cambridge University Press
ISBN: 9780521781244
Category : Mathematics
Languages : en
Pages : 240
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Book Description
Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.
Author: Eric Garnier
Publisher: Springer Science & Business Media
ISBN: 9048128196
Category : Science
Languages : en
Pages : 280
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Book Description
This book addresses both the fundamentals and the practical industrial applications of Large Eddy Simulation (LES) in order to bridge the gap between LES research and the growing need to use it in engineering modeling.
Author: Peter R. Voke
Publisher: Springer Science & Business Media
ISBN: 940111000X
Category : Technology & Engineering
Languages : en
Pages : 438
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Book Description
It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.
Author: P. Sagaut
Publisher: Springer Science & Business Media
ISBN: 9783540263449
Category : Computers
Languages : en
Pages : 600
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Book Description
First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."
