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Stochastic Coherent Adaptive Large Eddy Simulation Method
, 2004
"... In this thesis the longstanding need for a dynamically adaptive Large Eddy Simulation (LES) method has been addressed. Current LES methodologies rely on, at best, a zonal grid adaptation strategy to attempt to minimize computational cost in resolving large eddies in complex turbulent flow simulation ..."
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Cited by 22 (8 self)
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In this thesis the longstanding need for a dynamically adaptive Large Eddy Simulation (LES) method has been addressed. Current LES methodologies rely on, at best, a zonal grid adaptation strategy to attempt to minimize computational cost in resolving large eddies in complex turbulent flow simulations. While an improvement over regular grids, these methodologies fail to resolve the high wave number components of the spatially intermittent coherent eddies that typify turbulent flows, thus not resolving valuable physical information. At the same time the flow is over resolved in regions between the intermittent coherent eddies. The Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) methodology addresses the shortcomings of LES by using a dynamic grid adaptation strategy that resolves the most energetic coherent structures in a turbulent flow field. This new methodology inherits from Coherent Vortex Simulation (CVS) the ability to dynamically resolve and “track” the most energetic part of the coherent eddies in a turbulent flow field, while using a field compression similar to LES, which could be considerably higher than with CVS. Unlike CVS, which is able to recover low order statistics with no subgrid scale stress model, the effect of the unresolved
CVS and SCALES simulations of 3D isotropic turbulence
 J. Turbul
, 2005
"... In this work coherent vortex simulation (CVS) and stochastic coherent adaptive large eddy simulation (SCALES) simulations of decaying incompressible isotropic turbulence are compared to DNS and large eddy simulation (LES) results. Current LES relies on, at best, a zonally adapted filter width to red ..."
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Cited by 8 (2 self)
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In this work coherent vortex simulation (CVS) and stochastic coherent adaptive large eddy simulation (SCALES) simulations of decaying incompressible isotropic turbulence are compared to DNS and large eddy simulation (LES) results. Current LES relies on, at best, a zonally adapted filter width to reduce the computational cost of simulating complex turbulent flows. While there is an improvement over auniform filter width, this approach has two limitations. First, it does not capture the high wave number components of the coherent vortices that make up the organized part of turbulent flows, thus losing essential physical information. Secondly, the flow is overresolved in the regions between the coherent vortices, thus wasting computational resources. The SCALES approach addresses these shortcomings of LES by using a dynamic grid adaptation strategy that is able to resolve and track the most energetic coherent structures in a turbulent flow field. This corresponds to a dynamically adaptive local filter width. Unlike CVS, which we show is able to recover low order statistics with no subgrid scale (SGS) stress model, the higher compression used in SCALES necessitates that the effect of the unresolved SGS stresses must be modeled. These SGS stresses are approximated using a new dynamic eddy viscosity model based on Germano’s classical dynamic procedure redefined in terms of two wavelet thresholding filters.
Hierarchical Multiscale Adaptive Variable Fidelity Waveletbased Turbulence Modeling with
, 2012
"... The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. iii ..."
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Cited by 3 (2 self)
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The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. iii
A variational multiscale method for incompressible . . .
, 2011
"... Residualbased turbulence model Variational multiscale method Large eddy simulation ual ploy tion ear finescale velocity field is assumed to be nonlinear and timedependent and is modeled via the bubble stabilization tensor that possesses the right order in the advective and diffusive limits, and v ..."
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Cited by 3 (3 self)
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Residualbased turbulence model Variational multiscale method Large eddy simulation ual ploy tion ear finescale velocity field is assumed to be nonlinear and timedependent and is modeled via the bubble stabilization tensor that possesses the right order in the advective and diffusive limits, and variationally ovides f turbu tion of methods for LES modeling, the reader could refer to [48,2,14,31,10,26,40,32,42,49,50] and references therein. In recent years new LES models that are based on the variational multiscale (VMS) framework proposed by Hughes et al. [22,23] have been presented. The first applications of the VMS method to the modeling of turbulence by Hughes et al. [24,25] were based on threelevel scale decomposition involving coarse, fine and the modeledscales. The early versions of VMSbased turbulence appropriate spaces of functions is linked to a decomposition of the computational scales into two overlapping components that are categorized as coarsescales and finescales, respectively. Typically the coarsescales are represented via the traditional finite element shape functions, while the finescales that lie in an infinitedimensional space, are defined to be the remaining part of the solution. The decoupling of the spaces of functions leads to the decomposition of the original problem into two subproblems, namely, the coarsescale subproblem and the finescale subproblem. The modeling aspect in the method lies in extracting the finescale solution from the nonlinear finescale subproblem. This
2008 Lagrangian dynamic SGS model for stochastic coherent adaptive large eddy simulation
 J. Turbul
"... Abstract. Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) is an extension of Large Eddy Simulation that uses a wavelet filterbased dynamic grid adaptation strategy to solve for the most energetic coherent structures in a turbulent flow field, while modelling the effect of the less energ ..."
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Abstract. Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) is an extension of Large Eddy Simulation that uses a wavelet filterbased dynamic grid adaptation strategy to solve for the most energetic coherent structures in a turbulent flow field, while modelling the effect of the less energetic ones. A localized dynamic subgrid scale model is needed to fully exploit the ability of the method to track coherent structures. In this paper, new local Lagrangian models based on a modified Germano dynamic procedure, redefined in terms of wavelet thresholding filters, are proposed. These models extend the original pathline formulation of Meneveau et al [J. Fluid Mech., 319, 1996] in two ways: as Lagrangian pathline diffusive and Lagrangian pathtube averaging procedures. The proposed models are tested for freely decaying homogeneous turbulence with initial Reλ = 72. It is shown that the SCALES results, obtained with fewer than 0.4 % of the total nonadaptive nodes required for a DNS with the same wavelet solver, closely match reference DNS data. In contrast to classical LES, this agreement holds not only for large scale global statistical quantities, but also for energy and, more importantly, enstrophy spectra up to the dissipative wavenumber range. ∗ To whom correspondence should be addressed (Oleg.Vasilyev@Colorado.edu) Lagrangian dynamic SGS model for SCALES 2 1.
COMPARISON OF LARGE EDDY SIMULATION METHODS FOR FLOWS OVER GAS TURBINE BLADES
"... ABSTRACT In recent years there has been a considerable effort toward applying large eddy simulation methods (LES) to real industrial problems. However, there are still several challenges to be addressed to achieve a reliable LES solution, especially in the context of compressible flows. Furthermore ..."
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ABSTRACT In recent years there has been a considerable effort toward applying large eddy simulation methods (LES) to real industrial problems. However, there are still several challenges to be addressed to achieve a reliable LES solution, especially in the context of compressible flows. Furthermore, complex geometries require the unstructured meshes which then interdict the use of very high order schemes. Therefore, LES models are mainly derived and tested on classical problem of simple geometry for incompressible flow and based on higher order schemes. Here, the flow over a gas turbine blade at high Reynolds and Mach numbers is investigated using a mixed finitevolumefiniteelement method. Implicit LES method (ILES) as well as Smagorinsky and its dynamic version have been studied. Different variations of the Smagorinsky method have been examined too. The interaction of the numerical dissipation of the scheme with LES models has been explored. The results show the capability of the ILES to take into account the effective viscosity of the flow and the negligible difference of the different LES models in this flow condition. Fairly good agreement with experimental data is found which is superior to RANS results. It is found that there are still some challenges in industrial LES applications which have to be addressed to lead to a better agreement with experimental data. INTRODUCTION Turbomachinery flows are, at least locally, turbulent. Traditionally, Reynolds Averaged NavierStokes (RANS) equations have been applied to model the largescale motions of these compressible turbulent flows. Large eddy simulation (LES) of turbulence by modeling only smallscales of the flow and simulating the large scales, proved to provide more accurate results ([1, 2] for a general presentation and comparison of different turbulence models). LES turbulence modeling is mostly applied and validated on simple geometries and classical problems. On the account of simplicity of the geometry usually very high order structured finite difference schemes are applied. Recently,
Residualbased turbulence models for moving boundary flows: hierarchical application of variational multiscale method and threelevel scale separation
, 2013
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