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Author: Songül Kaya Merdan
Publisher: LAP Lambert Academic Publishing
ISBN: 9783845432083
Category :
Languages : en
Pages : 80
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Book Description
Despite efforts of more than centuries, turbulence phenomena is categorized as an unsolved problem. Turbulence is part of everyday's life. The majority of flows of industrial and technological applications are turbulent; natural flows are invariably so. There are many important and interesting physical phenomena which are connected with turbulent flows. Turbulence is observed in natural and engineering applications such as in weather prediction, air pollution, water pollution, aerodynamics and heat exchangers. This work considers an accurate and reliable solutions of turbulent flows. It is concerned with one of the most promising approaches to the numerical simulation of turbulent flows, the subgrid eddy viscosity models. We analyze both continuous and discontinuous finite element approximation of the new subgrid eddy viscosity model. This approach has the advantage that the diffusivity is introduced only on the small scales of the flow. Numerical test shows the new stabilization technique is robust and efficient in solving Navier-Stokes equations for a wide range of Reynolds numbers.
Author: Songül Kaya Merdan
Publisher: LAP Lambert Academic Publishing
ISBN: 9783845432083
Category :
Languages : en
Pages : 80
Get Book Here
Book Description
Despite efforts of more than centuries, turbulence phenomena is categorized as an unsolved problem. Turbulence is part of everyday's life. The majority of flows of industrial and technological applications are turbulent; natural flows are invariably so. There are many important and interesting physical phenomena which are connected with turbulent flows. Turbulence is observed in natural and engineering applications such as in weather prediction, air pollution, water pollution, aerodynamics and heat exchangers. This work considers an accurate and reliable solutions of turbulent flows. It is concerned with one of the most promising approaches to the numerical simulation of turbulent flows, the subgrid eddy viscosity models. We analyze both continuous and discontinuous finite element approximation of the new subgrid eddy viscosity model. This approach has the advantage that the diffusivity is introduced only on the small scales of the flow. Numerical test shows the new stabilization technique is robust and efficient in solving Navier-Stokes equations for a wide range of Reynolds numbers.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 196
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Book Description
Accurate and efficient turbulence simulation in complex geometries is a formidable chal-lenge. Traditional methods are often limited by low accuracy and/or restrictions to simplegeometries. We explore the merger of Discontinuous Galerkin (DG) spatial discretizationswith Variational Multi-Scale (VMS) modeling, termed Local VMS (LVMS), to overcomethese limitations. DG spatial discretizations support arbitrarily high-order accuracy on un-structured grids amenable for complex geometries. Furthermore, high-order, hierarchicalrepresentation within DG provides a natural framework fora prioriscale separation crucialfor VMS implementation. We show that the combined benefits of DG and VMS within theLVMS method leads to promising new approach to LES for use in complex geometries. The efficacy of LVMS for turbulence simulation is assessed by application to fully-developed turbulent channelflow. First, a detailed spatial resolution study is undertakento record the effects of the DG discretization on turbulence statistics. Here, the localhp refinement capabilites of DG are exploited to obtain reliable low-order statistics effi-ciently. Likewise, resolution guidelines for simulating wall-bounded turbulence using DGare established. We also explore the influence of enforcing Dirichlet boundary conditionsindirectly through numericalfluxes in DG which allows the solution to jump (slip) at thechannel walls. These jumps are effective in simulating the influence of the wall commen-surate with the local resolution and this feature of DG is effective in mitigating near-wallresolution requirements. In particular, we show that by locally modifying the numericalviscousflux used at the wall, we are able to regulate the near-wall slip through a penaltythat leads to improved shear-stress predictions. This work, demonstrates the potential ofthe numerical viscousflux to act as a numerically consistent wall-model and this successwarrents future research. As in any high-order numerical method some mechanism is required to control aliasingeffects due to nonlinear interactions and to ensure nonlinear stability of the method. Inthis context, we evaluate the merits of two approaches to de-aliasing -- spectralfilteringand polynomial dealiasing. While both approaches are successful, polynomial-dealiasingis found to be better suited for use in large-eddy simulation. Finally, results using LVMSare reported and show good agreement with reference direct numerical simulation therebydemonstrating the effectiveness of LVMS for wall-bounded turbulence. This success pavesthe way for future applications of LVMS to more complex turbulentflows. 3.
Author: Robert Moser
Publisher: Elsevier
ISBN: 032399833X
Category : Science
Languages : en
Pages : 568
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Book Description
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
Author: Pierre Sagaut
Publisher: World Scientific
ISBN: 1848169876
Category : Science
Languages : en
Pages : 446
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Book Description
The book aims to provide the reader with an updated general presentation of multiscale/multiresolution approaches in turbulent flow simulations. All modern approaches (LES, hybrid RANS/LES, DES, SAS) are discussed and recast in a global comprehensive framework. Both theoretical features and practical implementation details are addressed. Some full scale applications are described, to provide the reader with relevant guidelines to facilitate a future use of these methods.
Author: William Layton
Publisher: MDPI
ISBN: 3038428094
Category : Mathematics
Languages : en
Pages : 229
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Book Description
This book is a printed edition of the Special Issue "Turbulence: Numerical Analysis, Modelling and Simulation" that was published in Fluids
Author: René de Borst
Publisher: Springer Science & Business Media
ISBN: 9048198097
Category : Computers
Languages : en
Pages : 451
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Book Description
This work gives a modern, up-to-date account of recent developments in computational multiscale mechanics. Both upscaling and concurrent computing methodologies will be addressed for a range of application areas in computational solid and fluid mechanics: Scale transitions in materials, turbulence in fluid-structure interaction problems, multiscale/multilevel optimization, multiscale poromechanics. A Dutch-German research group that consists of qualified and well-known researchers in the field has worked for six years on the topic of computational multiscale mechanics. This text provides a unique opportunity to consolidate and disseminate the knowledge gained in this project. The addition of chapters written by experts outside this working group provides a broad and multifaceted view of this rapidly evolving field.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The work performed as part of this grant may be described in the context of developing numerical methods for solving an abstract, nonlinear variational problem for which the straightforward Galerkin approximation on a space of reasonable dimension is inaccurate. Target applications include flows with turbulence and systems with shocks. With this in mind, an alternate finite dimensional problem is proposed in which a model term (with unknown parameters) is added to the Galerkin approximation to improve its performance. We have developed new formulations for this model term especially for turbulent flows and for systems with shocks. We have also developed a dynamic approach for evaluating the parameters that appear in this model term. We have conducted several numerical studies to confirm the usefulness of the proposed approach.
Author: Elaine Cohen
Publisher: CRC Press
ISBN: 1439864209
Category : Computers
Languages : en
Pages : 638
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Book Description
Written by researchers who have helped found and shape the field, this book is a definitive introduction to geometric modeling. The authors present all of the necessary techniques for curve and surface representations in computer-aided modeling with a focus on how the techniques are used in design. They achieve a balance between mathematical rigor
Author: Tomás Chacón Rebollo
Publisher: Springer
ISBN: 1493904558
Category : Mathematics
Languages : en
Pages : 530
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Book Description
With applications to climate, technology, and industry, the modeling and numerical simulation of turbulent flows are rich with history and modern relevance. The complexity of the problems that arise in the study of turbulence requires tools from various scientific disciplines, including mathematics, physics, engineering and computer science. Authored by two experts in the area with a long history of collaboration, this monograph provides a current, detailed look at several turbulence models from both the theoretical and numerical perspectives. The k-epsilon, large-eddy simulation and other models are rigorously derived and their performance is analyzed using benchmark simulations for real-world turbulent flows. Mathematical and Numerical Foundations of Turbulence Models and Applications is an ideal reference for students in applied mathematics and engineering, as well as researchers in mathematical and numerical fluid dynamics. It is also a valuable resource for advanced graduate students in fluid dynamics, engineers, physical oceanographers, meteorologists and climatologists.
Author: Farshad Navah
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"This work discusses the development, the verification and the validation of high-order (of accuracy) solvers for the simulation of turbulent fluid flows. In a first part, a methodology for the verification of high-order solvers is proposed which examines the implementation, in a given computer software, of mathematical models that represent the flow dynamics. The method of manufactured solutions is adopted which allows for the exact evaluation of discretization errors and observed orders of accuracy. The latter are compared to the theoretical orders of accuracy for a variety of increasingly complex problems, starting from unbounded (by walls) inviscid flows and gradually reaching the case of realistic turbulent boundary layers, modelled by the Reynolds-averaged Navier-Stokes equations, along with the original and the negative Spalart-Allmaras closure models. Each case serves to illustrate and discuss salient aspects of the proposed methodology.Code verification via manufactured solutions is furthermore distinguished from solution verification and the latter is extended to high-order frameworks by describing the approach for error estimation via extrapolation of high-order solutions which is applied, as an example, to the case of turbulent flow over a flat plate. This exercise enabled the exploration into the question of high-order grid convergence for various output quantities of interest as well as the question of uncertainty analysis. This pointed at the inadequacy of substituting solution verification to proper high-order solver verification, even for a relatively simple problem and an expert set of grids. It is therefore recommended to use the solutions of actual problems for engineering and science applications, only along with estimated numerical uncertainties, especially for lower orders which are more error-prone. In the second part of this work, a compact high-order variational multiscale method for the large-eddy simulation of turbulence is devised and validated. The existing multiscale method is thus expanded from modal frameworks to a large family of compact high-order nodal schemes, represented by the recent flux reconstruction discretization method. The potential of the proposed formulation is then assessed on a Taylor-Green vortex problem and its results are validated against the filtered data from direct numerical simulations. It is thus revealed that proper de-aliasing is mandatory to conserve the quality of high-order large-eddy simulation. Furthermore, reducing the numerical dissipation of Roe's Riemann solver is found to contribute to improving low-Mach flow solutions for variational multiscale methods. Finally, the proposed variational-multiscale formulation resulted in noticeable improvements over the baseline implicit as well as the classical large-eddy simulations." --
