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Explicitly Filtered Large Eddy Simulation
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Book Synopsis Explicitly Filtered Large-eddy Simulation by : Sanjeeb T. Bose
Download or read book Explicitly Filtered Large-eddy Simulation written by Sanjeeb T. Bose and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The governing equations for large-eddy simulation (LES) are derived from the application of a low-pass filter to the Navier-Stokes equations. LES has shown to be a tractable method for the computation of high Reynolds number turbulent flows, primarily because the filtration of the Navier-Stokes equations removes the small scales of motion that would otherwise impose prohibitive resolution requirements. The effect of the scales of motion that are smaller than the filter width on the large, resolved scales are then modeled. In practice, the filter used to derive the LES governing equation is not formally defined and instead, it is assumed that the discretization of LES equation will implicitly act as a low-pass filter. This study investigates an alternative derivation of the LES governing equations that requires the formal definition of the filtration operator, known as explicitly filtered LES. It is shown that decoupling the filtering operation from the underlying grid allows for the isolation of subgrid-scale (SGS) modeling errors from numerical discretization errors. In this grid-independent context, it is demonstrated that standard eddy viscosity models are inaccurate at coarse resolutions. By leveraging the definition of the filtering operator, an SGS model is subsequently derived from a low order perturbation of the explicitly filtered governing equations. LES of canonical wall bounded flows (e.g., channels and ducts) at coarse resolutions validate the improved accuracy of the proposed SGS model. Simulations of practical engineering configurations require the ability to handle complex geometries. Previous explicitly filtered LES calculations have been limited to structured grid discretizations because of the difficulty in constructing a low-pass filter on unstructured grids. The explicitly filtered framework and the proposed SGS model are extended for use in unstructured grid environments through the use of differential filters. Unstructured grids also provide the ability to locally increase resolution in regions of the flow where the SGS model is unable to accurately model the stress provided by the unresolved scales of motion. A novel adaptation technique is suggested where the mesh (and/or filter) is refined in regions of the flow where estimates of the SGS fluctuations are largest. An LES of a three-dimensional stalled diffuser is performed to demonstrate the efficacy of the SGS model based mesh refinement criteria and the capabilities of the differential filters on unstructured grids. Lastly, a dynamic wall boundary condition is derived from the differential filter for wall-modeled large-eddy simulation where the near wall turbulence is not resolved. This differential filter based wall model successfully predicts mean dynamics of both wall-bounded flows (channels) and separating flows in complex geometries (airfoil at near-stall conditions) without the prescription of any ad hoc coefficients or RANS/LES hybridization.
Book Synopsis Grid-Independent Large-Eddy Simulation in Turbulent Channel Flow Using Three-Dimensional Explicit Filtering by : Jessica Gullbrand
Download or read book Grid-Independent Large-Eddy Simulation in Turbulent Channel Flow Using Three-Dimensional Explicit Filtering written by Jessica Gullbrand and published by . This book was released on 2003 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most commonly used Large Eddy Simulation (LES) approach is the implicitly filtered approach. In implicitly filtered LES, the computational grid and the discretization operators are considered as the filtering of the governing equations. Thereby the turbulent flow field is divided into grid resolved and unresolved scales, where the unresolved scales must be modeled. When explicit filtering is used in LES, the filtering procedure of the governing equations is separated from the grid and discretization operations. The flow field is divided into resolved filtered scale (RFS) motions, and subfilter-scale (SFS) motions. The SFS is itself divided into a resolved part (RSFS) and an unresolved part (USFS) (Zhou et at. 2001); see figure 1. The RFS motion is obtained by solving the filtered Navier-Stokes equations. The RSFS motions can be reconstructed from the resolved field and occur due to the use of a smooth (in spectral space) filter function. The USFS motions consist of scales that are not resolved in the simulation and need to be modeled. The explicitly filtered governing equations were recently studied by Carati et al. (2001) in forced isotropic turbulence.
Book Synopsis Large-Eddy Simulations on Unstructured Grids Using Explicit Differential Filters in Approximate Deconvolution Models by : Mostafa Najafiyazdi
Download or read book Large-Eddy Simulations on Unstructured Grids Using Explicit Differential Filters in Approximate Deconvolution Models written by Mostafa Najafiyazdi and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In Computational Aeroacoustic (CAA) applications of Large-Eddy Simulations (LES), accurate control over turbulent kinetic energy (TKE) dissipation is needed to minimize aliasing and obtain accurate broad-band noise estimations. Among different LES approaches, Approximate Deconvolution Models (ADM) allow direct control of the TKE dissipation rate for the resolvable wavenumber scales. This control is obtained by applying an explicitly defined spatial filter on the computed flow fields. InADM schemes, filtered Navier-Stokes equations are used where the filtering operator is explicitly defined. Approximate deconvolution approaches are used to estimate the unfiltered quantities used in constructing the nonlinear flux terms. Given a filter operator, the energy dissipation associated with filtering can be quantified. ADM has been successfully applied on structured grids using discrete high-order filter operators. Its application on unstructured grid has been very limited due to lack of a proper filter.The objective of the present work was to extend the application of Approximate Deconvolution Models (ADM) for LES on unstructured grids by using explicit differential filters. Germano’s elliptic differential filter was successfully extended to include two free parameters. One ensured full attenuation at grid cut-off wavenumber, preventing aliasing due to LES and stabilizing the numerical scheme. The other controlled the filter cut-off wavenumber. The discretized formulation of this differential filter was developed for two- and three-dimensional elements. Dissipation and dispersion properties of the discrete differential filter were investigated in detail.A second-order classical finite element method (FEM) was used for spatial discretization of the compressible Navier-Stokes equations. Time integration was performed through the use of the standard fourth-order explicit Runge-Kutta scheme. Interpolation on high resolution grids was used to obtain the fast Fourier transform (FFT) of the flow fields on perturbed and unstructured grids.Decaying isotropic homogeneous turbulence at Reynolds number 3, 400 was modeled on both structured and unstructured grids. Results were compared to a reference direct numerical simulation (DNS) and other LES results reported in the literature. The effect of mesh anisotropy on the newly proposed differential filter performance was studied. It was observed that stable and sufficiently accurate LES results could be obtained on unstructured grids, even in the presence of highly skewed elements. Careful examination of the dissipation rate in the resolved wavenumbers suggested that grid anisotropy induces different cut-off wavenumbers in different directions resulting in higher dissipation rates than those obtained on an isotropic mesh.Taylor-Green vortex (TGV) was also studied as an excellent canonical problem for laminar to turbulence transition of a flow. LES simulations using the ADM framework were conducted in which the filter extended to three-dimensional elements was used. Investigative studies on the ADM order, the ADM under-relaxation coefficient, the degree of anisotropy in the grid, and grid resolution were performed to benchmark the filter performance in conjunction with ADM. Finally, an LES of TGV on a fully unstructured grid was performed showing the range of application of the proposed filter"--
Book Synopsis Large Eddy Simulation for Compressible Flows by : Eric Garnier
Download or read book Large Eddy Simulation for Compressible Flows written by Eric Garnier and published by Springer Science & Business Media. This book was released on 2009-08-11 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Design and Application of Discrete Explicit Filters by : Deconinck Willem
Download or read book Design and Application of Discrete Explicit Filters written by Deconinck Willem and published by LAP Lambert Academic Publishing. This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the context of Large Eddy Simulation (LES) of turbulent flows, there is a current need to compare and evaluate different proposed subfilter-scale models in order to assess their suitability for various applications. In order to carefully compare subfilter-scale models and compare LES predictions to Direct Numerical Simulation (DNS) results (the latter would be helpful in the comparison and validation of models), there is a real need for a "grid-independent" LES capability and explicit filtering methods offer one means by which this may be achieved. Advantages of explicit filtering are that it provides a means for eliminating aliasing errors, allows for the direct control of commutation errors, and most importantly allows a decoupling between the mesh spacing and the filter width which is the primary reason why there are difficulties in comparing LES solutions obtained on different grids. This book considers the design and assessment of discrete explicit filters and their application to isotropic turbulence prediction. This book was submitted for the degree of Masters of Applied Science at the Graduate Department of Aerospace Engineering at the University of Toronto.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721608942 Total Pages :26 pages Book Rating :4.6/5 (89 download)
Book Synopsis Grid-Independent Large-Eddy Simulation in Turbulent Channel Flow Using Three-Dimensional Explicit Filtering by : National Aeronautics and Space Administration (NASA)
Download or read book Grid-Independent Large-Eddy Simulation in Turbulent Channel Flow Using Three-Dimensional Explicit Filtering written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-21 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, turbulence-closure models are evaluated using the 'true' LES approach in turbulent channel flow. The study is an extension of the work presented by Gullbrand (2001), where fourth-order commutative filter functions are applied in three dimensions in a fourth-order finite-difference code. The true LES solution is the grid-independent solution to the filtered governing equations. The solution is obtained by keeping the filter width constant while the computational grid is refined. As the grid is refined, the solution converges towards the true LES solution. The true LES solution will depend on the filter width used, but will be independent of the grid resolution. In traditional LES, because the filter is implicit and directly connected to the grid spacing, the solution converges towards a direct numerical simulation (DNS) as the grid is refined, and not towards the solution of the filtered Navier-Stokes equations. The effect of turbulence-closure models is therefore difficult to determine in traditional LES because, as the grid is refined, more turbulence length scales are resolved and less influence from the models is expected. In contrast, in the true LES formulation, the explicit filter eliminates all scales that are smaller than the filter cutoff, regardless of the grid resolution. This ensures that the resolved length-scales do not vary as the grid resolution is changed. In true LES, the cell size must be smaller than or equal to the cutoff length scale of the filter function. The turbulence-closure models investigated are the dynamic Smagorinsky model (DSM), the dynamic mixed model (DMM), and the dynamic reconstruction model (DRM). These turbulence models were previously studied using two-dimensional explicit filtering in turbulent channel flow by Gullbrand & Chow (2002). The DSM by Germano et al. (1991) is used as the USFS model in all the simulations. This enables evaluation of different reconstruction models for the RSFS stresses. The DMM co
Book Synopsis Direct and Large-Eddy Simulation by : Bernard J. Geurts
Download or read book Direct and Large-Eddy Simulation written by Bernard J. Geurts and published by Walter de Gruyter GmbH & Co KG. This book was released on 2022-12-05 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of the mathematics and physics behind the simulation of turbulent flows and discusses in detail (i) the phenomenology of turbulence in fluid dynamics, (ii) the role of direct and large-eddy simulation in predicting these dynamics, (iii) the multiple considerations underpinning subgrid modelling, and, (iv) the issue of validation and reliability resulting from interacting modelling and numerical errors.
Book Synopsis Design and Application of Discrete Explicit Filters for Large Eddy Simulation of Compressible Turbulent Flows by : Willem Deconinck
Download or read book Design and Application of Discrete Explicit Filters for Large Eddy Simulation of Compressible Turbulent Flows written by Willem Deconinck and published by . This book was released on 2008 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the context of Large Eddy Simulation (LES) of turbulent flows, there is a current need to compare and evaluate different proposed subfilter-scale models. In order to carefully compare subfilter-scale models and compare LES predictions to Direct Numerical Simulation (DNS) results (the latter would be helpful in the comparison and validation of models), there is a real need for a "grid-independent" LES capability and explicit filtering methods offer one means by which this may be achieved. Advantages of explicit filtering are that it provides a means for eliminating aliasing errors, allows for the direct control of commutation errors, and most importantly allows a decoupling between the mesh spacing and the filter width which is the primary reason why there are difficulties in comparing LES solutions obtained on different grids. This thesis considers the design and assessment of discrete explicit filters and their application to isotropic turbulence prediction.
Book Synopsis Large Eddy Simulation for Incompressible Flows by : P. Sagaut
Download or read book Large Eddy Simulation for Incompressible Flows written by P. Sagaut and published by Springer Science & Business Media. This book was released on 2006 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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."
Book Synopsis Explicit Filtering in Large Eddy Simulation Using a Discontinuous Galerkin Method by : Matthew J. Brazell
Download or read book Explicit Filtering in Large Eddy Simulation Using a Discontinuous Galerkin Method written by Matthew J. Brazell and published by . This book was released on 2015 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discontinuous Galerkin (DG) method is a formulation of the finite element method (FEM). DG provides the ability for a high order of accuracy in complex geometries, and allows for highly efficient parallelization algorithms. These attributes make the DG method attractive for solving the Navier-Stokes equations for large eddy simulation (LES). The main goal of this work is to investigate the feasibility of adopting an explicit filter in the numerical solution of the Navier-Stokes equations with DG. Explicit filtering has been shown to increase the numerical stability of under-resolved simulations and is needed for LES with dynamic sub-grid scale (SGS) models. The explicit filter takes advantage of DG’s framework where the solution is approximated using a polyno- mial basis where the higher modes of the solution correspond to a higher order polynomial basis. By removing high order modes, the filtered solution contains low order frequency content much like an explicit low pass filter. The explicit filter implementation is tested on a simple 1-D solver with an initial condi- tion that has some similarity to turbulent flows. The explicit filter does restrict the resolution as well as remove accumulated energy in the higher modes from aliasing. However, the ex- plicit filter is unable to remove numerical errors causing numerical dissipation. A second test case solves the 3-D Navier-Stokes equations of the Taylor-Green vortex flow (TGV). The TGV is useful for SGS model testing because it is initially laminar and transitions into a fully turbulent flow. The SGS models investigated include the constant coefficient Smagorinsky model, dynamic Smagorinsky model, and dynamic Heinz model. The constant coefficient Smagorinsky model is over dissipative, this is generally not desirable however it does add stability. The dynamic Smagorinsky model generally performs better, especially during the laminar-turbulent transition region as expected. The dynamic Heinz model which is based on an improved model, handles the laminar-turbulent transition region well while also showing additional robustness.
Book Synopsis Large Eddy Simulation for Incompressible Flows by : P. Sagaut
Download or read book Large Eddy Simulation for Incompressible Flows written by P. Sagaut and published by Springer Science & Business Media. This book was released on 2013-04-18 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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."
Book Synopsis Modeling and Simulation of Turbulent Combustion by : Santanu De
Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.
Book Synopsis Large Eddy Simulation for Incompressible Flows by : Pierre Sagaut
Download or read book Large Eddy Simulation for Incompressible Flows written by Pierre Sagaut and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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."
Author :Luigi Carlo Berselli Publisher :Springer Science & Business Media ISBN 13 :9783540263166 Total Pages :378 pages Book Rating :4.2/5 (631 download)
Book Synopsis Mathematics of Large Eddy Simulation of Turbulent Flows by : Luigi Carlo Berselli
Download or read book Mathematics of Large Eddy Simulation of Turbulent Flows written by Luigi Carlo Berselli and published by Springer Science & Business Media. This book was released on 2006 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Book Synopsis Direct and Large-Eddy Simulation IV by : Bernard Geurts
Download or read book Direct and Large-Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.
Book Synopsis Direct and Large-Eddy Simulation VII by : Vincenzo Armenio
Download or read book Direct and Large-Eddy Simulation VII written by Vincenzo Armenio and published by Springer Science & Business Media. This book was released on 2010-04-28 with total page 575 pages. Available in PDF, EPUB and Kindle. Book excerpt: After Surrey in 1994, Grenoble in 1996, Cambridge in 1999, Enschede in 2001, Munich in 2003 and Poiters in 2005, the 7th Workshop, DLES7, will be held in Trieste, again under the auspices of ERCOFTAC. Following the spirit of the series, the goal of this latest 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 should once again be a unique opportunity for discussions about the more recent advances in the prediction, understanding and control of turbulent flows in academic or industrial situations.
Author :Maria Vittoria Salvetti Publisher :Springer Science & Business Media ISBN 13 :9400702310 Total Pages :442 pages Book Rating :4.4/5 (7 download)
Book Synopsis Quality and Reliability of Large-Eddy Simulations II by : Maria Vittoria Salvetti
Download or read book Quality and Reliability of Large-Eddy Simulations II written by Maria Vittoria Salvetti and published by Springer Science & Business Media. This book was released on 2010-11-03 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second Workshop on "Quality and Reliability of Large-Eddy Simulations", QLES2009, was held at the University of Pisa from September 9 to September 11, 2009. Its predecessor, QLES2007, was organized in 2007 in Leuven (Belgium). The focus of QLES2009 was on issues related to predicting, assessing and assuring the quality of LES. The main goal of QLES2009 was to enhance the knowledge on error sources and on their interaction in LES and to devise criteria for the prediction and optimization of simulation quality, by bringing together mathematicians, physicists and engineers and providing a platform specifically addressing these aspects for LES. Contributions were made by leading experts in the field. The present book contains the written contributions to QLES2009 and is divided into three parts, which reflect the main topics addressed at the workshop: (i) SGS modeling and discretization errors; (ii) Assessment and reduction of computational errors; (iii) Mathematical analysis and foundation for SGS modeling.
