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Parviz Moin - One of the best experts on this subject based on the ideXlab platform.
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a dynamic global Coefficient subgrid scale Model for large eddy simulation of turbulent scalar transport in complex geometries
Physics of Fluids, 2009Co-Authors: Donghyun You, Parviz MoinAbstract:The dynamic global-Coefficient subgrid-scale eddy-viscosity Model by You and Moin [Phys. Fluids 19, 065110 (2007)] is generalized for large-eddy simulation of turbulent flow with scalar transport. The Model Coefficient for subgrid-scale scalar flux which is constant in space but varies in time is dynamically determined based on the “global conservation” of the transport equation for scalar variance. Large-eddy simulations of turbulent flow with passive scalar transport through a channel and over a backward-facing step show that the present Model has a similar predictive capability as the dynamic Smagorinsky Model. The present dynamic Model is especially suitable for large-eddy simulation of turbulent flow with scalar transport in complex geometries since it does not require any spatial and temporal averaging or clipping of the Model Coefficient for numerical stabilization and requires only a single-level test filter. The present Model is not more complicated in implementation and not more expensive in ter...
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a dynamic global Coefficient subgrid scale eddy viscosity Model for large eddy simulation in complex geometries
Physics of Fluids, 2007Co-Authors: Donghyun You, Parviz MoinAbstract:An improvement of the dynamic procedure of Park et al. [Phys. Fluids 18, 125109 (2006)] for closure of the subgrid-scale eddy-viscosity Model developed by Vreman [Phys. Fluids 16, 3670 (2004)] is proposed. The Model Coefficient which is globally constant in space but varies in time is dynamically determined assuming the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation of which utilization was proposed by Park et al. Like the Vreman Model with a fixed Coefficient and the dynamic-Coefficient Model of Park et al., the present Model predicts zero eddy-viscosity in regions where the vanishing eddy viscosity is theoretically expected. The present dynamic Model is especially suitable for large-eddy simulation in complex geometries since it does not require any ad hoc spatial and temporal averaging or clipping of the Model Coefficient for numerical stabilization and more importantly, requires only a single-level test filter in contrast to the dynamic Model of Park et al., whi...
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application of a dynamic global Coefficient subgrid scale Model for large eddy simulation in complex geometries
ASME JSME 2007 5th Joint Fluids Engineering Conference, 2007Co-Authors: Donghyun You, Parviz MoinAbstract:The application of a dynamic global-Coefficient subgrid-scale eddy-viscosity Model for large-eddy simulation in complex geometries is presented. The Model employs a dynamic procedure for closure of the subgrid-scale eddy-viscosity Model developed by Vreman [Phys. Fluids 16 , 3670 (2004)]. The Model Coefficient which is globally constant in space but varies in time is dynamically determined assuming the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation of which utilization was proposed by Park et al. [Phys. Fluids 18 , 125109 (2006)]. Like the Vreman’s Model with a fixed Coefficient and the dynamic-Coefficient Model of Park et al., the present Model predicts zero eddy-viscosity in regions where the vanishing eddy viscosity is theoretically expected. The present dynamic Model is especially suitable for large-eddy simulation in complex geometries since it does not require any ad hoc spatial and temporal averaging or clipping of the Model Coefficient for numerical stabilization and requires only a single-level test filter.Copyright © 2007 by ASME
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a dynamic localization Model for large eddy simulation of turbulent flows
Journal of Fluid Mechanics, 1995Co-Authors: Sandip Ghosal, Thomas S. Lund, Parviz Moin, Knut AkselvollAbstract:In a previous paper, Germano, et al. (1991) proposed a method for computing Coefficients of subgrid-scale eddy viscosity Models as a function of space and time. This procedure has the distinct advantage of being self-calibrating and requires no a priori specification of Model Coefficients or the use of wall damping functions. However, the original formulation contained some mathematical inconsistencies that limited the utility of the Model. In particular, the applicability of the Model was restricted to flows that are statistically homogeneous in at least one direction. These inconsistencies and limitations are discussed and a new formulation that rectifies them is proposed. The new formulation leads to an integral equation whose solution yields the Model Coefficient as a function of position and time. The method can be applied to general inhomogeneous flows and does not suffer from the mathematical inconsistencies inherent in the previous formulation. The Model has been tested in isotropic turbulence and in the flow over a backward-facing step.
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a dynamic subgrid scale eddy viscosity Model
Physics of Fluids, 1991Co-Authors: Massimo Germano, Ugo Piomelli, Parviz Moin, William H CabotAbstract:One major drawback of the eddy viscosity subgrid‐scale stress Models used in large‐eddy simulations is their inability to represent correctly with a single universal constant different turbulent fields in rotating or sheared flows, near solid walls, or in transitional regimes. In the present work a new eddy viscosity Model is presented which alleviates many of these drawbacks. The Model Coefficient is computed dynamically as the calculation progresses rather than input a p r i o r i. The Model is based on an algebraic identity between the subgrid‐scale stresses at two different filtered levels and the resolved turbulent stresses. The subgrid‐scale stresses obtained using the proposed Model vanish in laminar flow and at a solid boundary, and have the correct asymptotic behavior in the near‐wall region of a turbulent boundary layer. The results of large‐eddy simulations of transitional and turbulent channel flow that use the proposed Model are in good agreement with the direct simulation data.
Haecheon Choi - One of the best experts on this subject based on the ideXlab platform.
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Dynamic global Model for large eddy simulation of transient flow
Physics of Fluids, 2010Co-Authors: Haecheon Choi, Noma ParkAbstract:In the present study, the dynamic subgrid-scale eddy viscosity Models with a global Model Coefficient by Park et al. [Phys. Fluids 18, 125109 (2006)] (called dynamic global Models hereafter) are applied to large eddy simulation of decaying isotropic turbulence to examine their performances in transient flow. The dynamic global Model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation fails to predict the temporal behavior of decaying isotropic turbulence. On the other hand, the dynamic global Model based on the Germano identity shows an excellent agreement with the experimental data of decaying isotropic turbulence.
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A dynamic subgrid-scale eddy viscosity Model with a global Model Coefficient
Physics of Fluids, 2006Co-Authors: Noma Park, Sungwon Lee, Jungil Lee, Haecheon ChoiAbstract:In the present study, a dynamic subgrid-scale eddy viscosity Model is proposed for large eddy simulation of turbulent flows in complex geometry. A subgrid-scale eddy viscosity Model recently proposed by Vreman [Phys. Fluids 16, 3670 (2004)] which guarantees theoretically zero subgrid-scale dissipation for various laminar shear flows, is considered as a base Model. A priori tests with the original Vreman Model show that it predicts the correct profile of subgrid-scale dissipation in turbulent channel flow but the optimal Model Coefficient is far from universal. A dynamic procedure of determining the Model Coefficient is proposed based on the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation. An important feature of the proposed procedure is that the Model Coefficient determined is globally constant in space but varies only in time. A posteriori tests of the proposed dynamic Model are conducted through large eddy simulations of forced isotropic turbulence at Reλ=103, tur...
Ugo Piomelli - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation of rotating channel flows using a localized dynamic Model
Physics of Fluids, 1995Co-Authors: Ugo Piomelli, Junhui LiuAbstract:Most applications of the dynamic subgrid‐scale stress Model use volume‐ or planar‐averaging to avoid ill‐conditioning of the Model Coefficient, which may result in numerical instabilities. Furthermore, a spatially‐varying Coefficient is mathematically inconsistent with the original derivation of the Model. A localization procedure is proposed here that removes the mathematical inconsistency to any desired order of accuracy in time. This Model is applied to the simulation of rotating channel flow, and results in improved prediction of the turbulence statistics. The Model Coefficient vanishes in regions of quiescent flow, reproducing accurately the intermittent character of the flow on the stable side of the channel. Large‐scale longitudinal vortices can be identified, consistent with the observation from experiments and direct simulations. The effect of the unresolved scales on higher‐order statistics is also discussed.
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high reynolds number calculations using the dynamic subgrid scale stress Model
Physics of Fluids, 1993Co-Authors: Ugo PiomelliAbstract:The dynamic subgrid‐scale eddy viscosity Model has been used in the large‐eddy simulation of the turbulent flow in a plane channel for Reynolds numbers based on friction velocity and channel half‐width ranging between 200 and 2000, a range including values significantly higher than in previous simulations. The computed wall stress, mean velocity, and Reynolds stress profiles compare very well with experimental and direct simulation data. Comparison of higher moments is also satisfactory. Although the grid in the near‐wall region is fairly coarse, the results are quite accurate: the turbulent kinetic energy peaks at y+≂12, and the near‐wall behavior of the resolved stresses is captured accurately. The Model Coefficient is o(10−3) in the buffer layer and beyond, where the cutoff wave numbers are in the decaying region of the spectra; in the near‐wall region the cutoff wave numbers are nearer the energy‐containing range, and the resolved turbulent stresses become a constant fraction of the resolved stresses....
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a dynamic subgrid scale eddy viscosity Model
Physics of Fluids, 1991Co-Authors: Massimo Germano, Ugo Piomelli, Parviz Moin, William H CabotAbstract:One major drawback of the eddy viscosity subgrid‐scale stress Models used in large‐eddy simulations is their inability to represent correctly with a single universal constant different turbulent fields in rotating or sheared flows, near solid walls, or in transitional regimes. In the present work a new eddy viscosity Model is presented which alleviates many of these drawbacks. The Model Coefficient is computed dynamically as the calculation progresses rather than input a p r i o r i. The Model is based on an algebraic identity between the subgrid‐scale stresses at two different filtered levels and the resolved turbulent stresses. The subgrid‐scale stresses obtained using the proposed Model vanish in laminar flow and at a solid boundary, and have the correct asymptotic behavior in the near‐wall region of a turbulent boundary layer. The results of large‐eddy simulations of transitional and turbulent channel flow that use the proposed Model are in good agreement with the direct simulation data.
Noma Park - One of the best experts on this subject based on the ideXlab platform.
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Dynamic global Model for large eddy simulation of transient flow
Physics of Fluids, 2010Co-Authors: Haecheon Choi, Noma ParkAbstract:In the present study, the dynamic subgrid-scale eddy viscosity Models with a global Model Coefficient by Park et al. [Phys. Fluids 18, 125109 (2006)] (called dynamic global Models hereafter) are applied to large eddy simulation of decaying isotropic turbulence to examine their performances in transient flow. The dynamic global Model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation fails to predict the temporal behavior of decaying isotropic turbulence. On the other hand, the dynamic global Model based on the Germano identity shows an excellent agreement with the experimental data of decaying isotropic turbulence.
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A dynamic subgrid-scale eddy viscosity Model with a global Model Coefficient
Physics of Fluids, 2006Co-Authors: Noma Park, Sungwon Lee, Jungil Lee, Haecheon ChoiAbstract:In the present study, a dynamic subgrid-scale eddy viscosity Model is proposed for large eddy simulation of turbulent flows in complex geometry. A subgrid-scale eddy viscosity Model recently proposed by Vreman [Phys. Fluids 16, 3670 (2004)] which guarantees theoretically zero subgrid-scale dissipation for various laminar shear flows, is considered as a base Model. A priori tests with the original Vreman Model show that it predicts the correct profile of subgrid-scale dissipation in turbulent channel flow but the optimal Model Coefficient is far from universal. A dynamic procedure of determining the Model Coefficient is proposed based on the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation. An important feature of the proposed procedure is that the Model Coefficient determined is globally constant in space but varies only in time. A posteriori tests of the proposed dynamic Model are conducted through large eddy simulations of forced isotropic turbulence at Reλ=103, tur...
Thomas S. Lund - One of the best experts on this subject based on the ideXlab platform.
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The dynamic Smagorinsky Model and scale-dependent Coefficients in the viscous range of turbulence
Physics of Fluids, 1997Co-Authors: Charles Meneveau, Thomas S. LundAbstract:The standard dynamic procedure is based on the scale-invariance assumption that the Model Coefficient C is the same at the grid and test-filter levels. In many applications this condition is not met. We consider the case when the filter-length, Δ, approaches the Kolmogorov scale, η, and C(Δ→η)→0. Using filtered direct numerical simulation data, we show that the standard dynamic Model yields the Coefficient corresponding to the test-filter scale (αΔ) instead of the grid scale (Δ). Several approaches to account for scale dependence in the dynamic Smagorinsky Model are considered, and the most robust of these is tested in large eddy simulation of forced isotropic turbulence at various Reynolds numbers.
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Dynamic Model with scale-dependent Coefficients in the viscous range
1996Co-Authors: Charles Meneveau, Thomas S. LundAbstract:The standard dynamic procedure is based on the scale-invariance assumption that the Model Coefficient C is the same at the grid and test-filter levels. In many applications this condition is not met, e.g. when the filter-length, delta, approaches the Kolmogorov scale, and C(delta approaches eta) approaches O. Using a priori tests, we show that the standard dynamic Model yields the Coefficient corresponding to the test-filter scale (alpha delta) instead of the grid-scale (delta). Several approaches to account for scale dependence are examined and/or tested in large eddy simulation of isotropic turbulence: (a) take the limit alpha approaches 1; (b) solve for two unknown Coefficients C(Delta) and C(alpha delta) in the least-square-error formulation; (c) the 'bi-dynamic Model', in which two test-filters (e.g. at scales 2(delta) and 4(delta) are employed to gain additional information on possible scale-dependence of the Coefficient, and an improved estimate for the grid-level Coefficient is obtained by extrapolation, (d) use theoretical predictions for the ratio C(alpha delta)/C(delta) and dynamically solve for C(delta). None of these options is found to be entirely satisfactory, although the last approach appears applicable to the viscous range.
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a dynamic localization Model for large eddy simulation of turbulent flows
Journal of Fluid Mechanics, 1995Co-Authors: Sandip Ghosal, Thomas S. Lund, Parviz Moin, Knut AkselvollAbstract:In a previous paper, Germano, et al. (1991) proposed a method for computing Coefficients of subgrid-scale eddy viscosity Models as a function of space and time. This procedure has the distinct advantage of being self-calibrating and requires no a priori specification of Model Coefficients or the use of wall damping functions. However, the original formulation contained some mathematical inconsistencies that limited the utility of the Model. In particular, the applicability of the Model was restricted to flows that are statistically homogeneous in at least one direction. These inconsistencies and limitations are discussed and a new formulation that rectifies them is proposed. The new formulation leads to an integral equation whose solution yields the Model Coefficient as a function of position and time. The method can be applied to general inhomogeneous flows and does not suffer from the mathematical inconsistencies inherent in the previous formulation. The Model has been tested in isotropic turbulence and in the flow over a backward-facing step.