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Explicit Filtering In Large Eddy Simulation Using A Discontinuous Galerkin Method
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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 in the Split Form Discontinuous Galerkin Method for the Compressible Navier-Stokes by : Anthony P. Edmonds
Download or read book Large Eddy Simulation in the Split Form Discontinuous Galerkin Method for the Compressible Navier-Stokes written by Anthony P. Edmonds and published by . This book was released on 2020 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discontinuous Galerkin (DG) method is a finite element method. The method is computationally efficient, scalable in parallel, and is capable of handling complex geometries; these attributes make the DG method popular for solving the Navier-Stokes equations .Traditional DG formulations utilize the weak form of the conservative equations, whereas there is a discretization that utilizes the strong formulation of these equations: this is called the split-form discretization. The goal of this work is to study large eddy simulation (LES) in the split-form discretization and contrast it with the standard weak form DG discretization. An explicit filtering operation is required for LES using a dynamic sub-grid scale (SGS) model referred to as the dynamic Smagorisnky model. Two modes of filtering were explored: a polynomial cutoff filter and a Laplacian filter. The polynomial cutoff filter works by removing high order modes. The high-order modes correspond to the high-order energy content of the solution. The Laplacian filter applies the Laplace operator to smooth out areas of the flow with large gradients. These areas correspond to this high-order energy content. The dynamic Smagorisnky model is analyzed along side the constant Smagorisnky model. The models were analyzed using the Taylor-Green vortex (TGV) problem. The TGV initially is laminar but then transitions to fully turbulent flow. This is an ideal candidate for studying the sub-grid scale (SGS) models used in LES; as this transition is a challenge. The constant Smagorisnky model is overly dissipative, and under predicts kinetic energy. The dynamic model performs better, however is far more costly to calculate. The split-form discretization is more dissipative than the standard DG formulation, however it is far more stable.
Book Synopsis Direct and Large Eddy Simulation XII by : Manuel García-Villalba
Download or read book Direct and Large Eddy Simulation XII written by Manuel García-Villalba and published by Springer Nature. This book was released on 2020-05-09 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 12th instalment in the bi-annual Workshop series on Direct and Large Eddy Simulation (DLES), which began in 1994 and focuses on modern techniques used to simulate turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structure. With the rapidly expanding capacities of modern computers, this approach has attracted more and more interest over the years and will undoubtedly be further enhanced and applied in the future. Hybrid modelling techniques based on a combination of LES and RANS approaches also fall into this category and are covered as well. The goal of the Workshop was to share the state of the art in DNS, LES and related techniques for the computation and modelling of turbulent and transitional flows. The respective papers highlight the latest advances in the prediction, understanding and control of turbulent flows in academic and industrial applications.
Book Synopsis Complex Effects in Large Eddy Simulations by : Stavros Kassinos
Download or read book Complex Effects in Large Eddy Simulations written by Stavros Kassinos and published by Springer Science & Business Media. This book was released on 2007-07-16 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of Large Eddy Simulations is reaching a level of maturity that brings this approach to the mainstream of engineering computations, while it opens opportunities and challenges. The main objective of this volume is to bring together leading experts in presenting the state-of-the-art and emerging approaches for treating complex effects in LES. A common theme throughout is the role of LES in the context of multiscale modeling and simulation.
Book Synopsis TILDA: Towards Industrial LES/DNS in Aeronautics by : Charles Hirsch
Download or read book TILDA: Towards Industrial LES/DNS in Aeronautics written by Charles Hirsch and published by Springer Nature. This book was released on 2021-06-28 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers detailed insights into new methods for high-fidelity CFD, and their industrially relevant applications in aeronautics. It reports on the H2020 TILDA project, funded by the European Union in 2015-2018. The respective chapters demonstrate the potential of high-order methods for enabling more accurate predictions of non-linear, unsteady flows, ensuring enhanced reliability in CFD predictions. The book highlights industrially relevant findings and representative test cases on the development of high-order methods for unsteady turbulence simulations on unstructured grids; on the development of the LES/DNS methodology by means of multilevel, adaptive, fractal and similar approaches for applications on unstructured grids; and on leveraging existent large-scale HPC networks to facilitate the industrial applications of LES/DNS in daily practice. Furthermore, the book discusses multidisciplinary applications of high-order methods in the area of aero-acoustics. All in all, it offers timely insights into the application and performance of high-order methods for CFD, and an extensive reference guide for researchers, graduate students, and industrial engineers whose work involves CFD and turbulence modeling.
Book Synopsis On the Use of Discontinuous Galerkin High Order Methods for Large Eddy Simulation by : David G. Flad
Download or read book On the Use of Discontinuous Galerkin High Order Methods for Large Eddy Simulation written by David G. Flad and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Direct and Large-Eddy Simulation IX by : Jochen Fröhlich
Download or read book Direct and Large-Eddy Simulation IX written by Jochen Fröhlich and published by Springer. This book was released on 2015-01-27 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume reflects the state of the art of numerical simulation of transitional and turbulent flows and provides an active forum for discussion of recent developments in simulation techniques and understanding of flow physics. Following the tradition of earlier DLES workshops, these papers address numerous theoretical and physical aspects of transitional and turbulent flows. At an applied level it contributes to the solution of problems related to energy production, transportation, magneto-hydrodynamics and the environment. A special session is devoted to quality issues of LES. The ninth Workshop on 'Direct and Large-Eddy Simulation' (DLES-9) was held in Dresden, April 3-5, 2013, organized by the Institute of Fluid Mechanics at Technische Universität Dresden. This book is of interest to scientists and engineers, both at an early level in their career and at more senior levels.
Book Synopsis Progress in Hybrid RANS-LES Modelling by : Sharath Girimaji
Download or read book Progress in Hybrid RANS-LES Modelling written by Sharath Girimaji and published by Springer. This book was released on 2015-02-20 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the Fifth Symposium on Hybrid RANS-LES Methods, which was held on March 19-21 in College Station, Texas, USA. The different chapters, written by leading experts, reports on the most recent developments in flow physics modelling, and gives a special emphasis to industrially relevant applications of hybrid RANS-LES methods and other turbulence-resolving modelling approaches. 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 (CFD), such as flow control, aero-acoustics, aero-elasticity and CFD-based multidisciplinary optimization. It discusses in particular advanced hybrid RANS-LES methods. Further topics include wall-modelled Large Eddy Simulation (WMLES) methods, embedded LES, and a comparison of the LES methods with both hybrid RANS-LES and URANS methods. Overall, the book provides readers with a snapshot on the state-of-the-art in CFD and turbulence modelling, with a special focus to hybrid RANS-LES methods and their industrial applications.
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.
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 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 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 Direct and Large-Eddy Simulation XI by : Maria Vittoria Salvetti
Download or read book Direct and Large-Eddy Simulation XI written by Maria Vittoria Salvetti and published by Springer. This book was released on 2019-02-02 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 11th workshop on Direct and Large Eddy Simulation (DLES), which was held in Pisa, Italy in May 2017. The event focused on modern techniques for simulating turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structures, as Direct Numerical Simulation (DNS), Large-Eddy Simulation (LES) or hybrid models based on a combination of LES and RANS approaches. In light of the growing capacities of modern computers, these approaches have been gaining more and more interest over the years and will undoubtedly be developed and applied further. The workshop offered a unique opportunity to establish a state-of-the-art of DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows and to discuss about recent advances and applications. This volume contains most of the contributed papers, which were submitted and further reviewed for publication. They cover advances in computational techniques, SGS modeling, boundary conditions, post-processing and data analysis, and applications in several fields, namely multiphase and reactive flows, convection and heat transfer, compressible flows, aerodynamics of airfoils and wings, bluff-body and separated flows, internal flows and wall turbulence and other complex flows.
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 Spectral/hp Element Methods for Computational Fluid Dynamics by : George Karniadakis
Download or read book Spectral/hp Element Methods for Computational Fluid Dynamics written by George Karniadakis and published by American Chemical Society. This book was released on 2013-01-10 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt: Revision of: Spectral/hp element methods for CFD. 1999.
Book Synopsis Advanced Computational Fluid and Aerodynamics by : Paul G. Tucker
Download or read book Advanced Computational Fluid and Aerodynamics written by Paul G. Tucker and published by Cambridge University Press. This book was released on 2016-03-15 with total page 589 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book outlines the computational fluid dynamics evolution and gives an overview of the methods available to the engineer.
