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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 Eddy-Viscosity model based on the invariants of the rate-of-strain
2011Co-Authors: Rwcp Verstappen, Jungil Lee, Sanjeeb Bose, H Choi, Parviz MoinAbstract:Large-Eddy simulation (LES) seeks to predict the dynamics of spatially filtered turbulent flows. By construction, the LES solution contains only scales of size ≥ ∆, where ∆ denotes some user-chosen length scale of the spatial filter. A large-Eddy simulation based on an Eddy-Viscosity model and a Navier-Stokes simulation differ only in diffusion coefficient. Therefore, we focus on the question: “When does Eddy diffusivity reduce a turbulent flow to eddies of size ≥ ∆?”. It is deduced that the Eddy Viscosity νe has to depend on the two invariants q and r of the filtered rate-of-strain tensor. We present a dynamic version of the resultant Eddy-Viscosity model and present results from LES of isotropic turbulence and turbulent channel flow.
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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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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.
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A dynamic subgrid-scale Eddy Viscosity model
Physics of Fluids A, 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 field 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 priori. The model is based on an algebraic identity (Germano 1990) 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.
William H Cabot - One of the best experts on this subject based on the ideXlab platform.
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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.
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A dynamic subgrid-scale Eddy Viscosity model
Physics of Fluids A, 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 field 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 priori. The model is based on an algebraic identity (Germano 1990) 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.
Charles Meneveau - One of the best experts on this subject based on the ideXlab platform.
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two point stress strain rate correlation structure and non local Eddy Viscosity in turbulent flows
Journal of Fluid Mechanics, 2021Co-Authors: Patricio Clark Di Leoni, Tamer A Zaki, George Em Karniadakis, Charles MeneveauAbstract:By analysing the Karman–Howarth equation for filtered-velocity fields in turbulent flows, we show that the two-point correlation between the filtered strain-rate and subfilter stress tensors plays a central role in the evolution of filtered-velocity correlation functions. Two-point correlation-based statistical a priori tests thus enable rigorous and physically meaningful studies of turbulence models. Using data from direct numerical simulations of isotropic and channel flow turbulence, we show that local Eddy-Viscosity models fail to exhibit the long tails observed in the real subfilter stress–strain-rate correlation functions. Stronger non-local correlations may be achieved by defining the Eddy-Viscosity model based on fractional gradients of order yields better results for the correlations in the streamwise direction, even well into the core channel region. In the spanwise direction, channel flow results show significantly more local interactions. The overall results confirm strong non-locality in the interactions between subfilter stresses and resolved-scale fluid deformation rates, but with non-trivial directional dependencies in non-isotropic flows. Hence, non-local operators thus exhibit interesting modelling capabilities and potential for large-Eddy simulations although more developments are required, both on the theoretical and computational implementation fronts.
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spectral and hyper Eddy Viscosity in high reynolds number turbulence
Journal of Fluid Mechanics, 2000Co-Authors: Stefano Cerutti, Charles Meneveau, Omar M KnioAbstract:For the purpose of studying the spectral properties of energy transfer between large and small scales in high-Reynolds-number turbulence, we measure the longitudinal subgrid-scale (SGS) dissipation spectrum, dened as the co-spectrum of the SGS stress and ltered strain-rate tensors. An array of four closely spaced X-wire probes enables us to approximate a two-dimensional box lter by averaging over dierent probe locations (cross-stream ltering) and in time (streamwise ltering using Taylor’s hypothesis). We analyse data taken at the centreline of a cylinder wake at Reynolds numbers up toR 450. Using the assumption of local isotropy, the longitudinal SGS stress and ltered strain-rate co-spectrum is transformed into a radial co-spectrum, which allows us to evaluate the spectral Eddy Viscosity, (k;k). In agreement with classical two-point closure predictions, for graded lters, the spectral Eddy Viscosity deduced from the box-ltered data decreases near the lter wavenumber k. When using a spectral cuto lter in the streamwise direction (with a box-lter in the crossstream direction) a cusp behaviour near the lter scale is observed. In physical space, certain features of a wavenumber-dependent Eddy Viscosity can be approximated by a combination of a regular and a hyper-Viscosity term. A hyper-viscous term is also suggested from considering equilibrium between production and SGS dissipation of resolved enstrophy. Assuming local isotropy, the dimensionless coecient of the hyper-viscous term can be related to the skewness coecient of ltered velocity gradients. The skewness is measured from the X-wire array and from direct numerical simulation of isotropic turbulence. The results show that the hyper-Viscosity coecient is negative for graded lters and positive for spectral lters. These trends are in agreement with the spectral Eddy Viscosity measured directly from the SGS stress{ strain rate co-spectrum. The results provide signicant support, now at high Reynolds numbers, for the ability of classical two-point closures to predict general trends of mean energy transfer in locally isotropic turbulence.
Massimo Germano - One of the best experts on this subject based on the ideXlab platform.
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on the Eddy Viscosity associated with the subgrid stresses
11th edition of the bi-annual Workshop series on Direct and Large-Eddy Simulation (DLES11), 2019Co-Authors: Andrea Cimarelli, Antonella Abba, Massimo GermanoAbstract:Thanks to its simplicity and robustness, the models based on the Eddy Viscosity concept represent the most common procedure to introduce the effect of the unresolved scales in the equations of motion for the Large Eddy Simulation (LES) approach. Indeed, the subgrid scale (sgs) Viscosity approach allows from an energetic point of view to respect the dissipative nature of turbulence.
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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.
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A dynamic subgrid-scale Eddy Viscosity model
Physics of Fluids A, 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 field 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 priori. The model is based on an algebraic identity (Germano 1990) 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.
Gianluca Iaccarino - One of the best experts on this subject based on the ideXlab platform.
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the deviation from parallel shear flow as an indicator of linear Eddy Viscosity model inaccuracy
Physics of Fluids, 2014Co-Authors: Catherine Gorle, Johan Larsson, Michael Emory, Gianluca IaccarinoAbstract:A marker function designed to indicate in which regions of a generic flow field the results from linear Eddy-Viscosity turbulence models are plausibly inaccurate is introduced. The marker is defined to identify regions that deviate from parallel shear flow. For two different flow fields it is shown that these regions largely coincide with regions where the prediction of the Reynolds stress divergence is inaccurate. The marker therefore offers a guideline for interpreting results obtained from Reynolds-averaged Navier-Stokes simulations and provides a basis for the further development of turbulence model-form uncertainty quantification methods.
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A subgrid-scale Eddy-Viscosity model based on the volumetric strain-stretching
Physics of Fluids, 2014Co-Authors: Sungmin Ryu, Gianluca IaccarinoAbstract:We propose a novel subgrid-scale (SGS) Eddy-Viscosity model for large Eddy simulation (LES) to accurately reproduce the effect of subgrid stresses on the resolved scales. The developed SGS model is based on the second-order volumetric strain-stretching (VSS) tensor, which is constructed by the multiplication of diagonal components of the strain-rate tensor with its off-diagonal components. The proposed VSS-model is validated in typical flow cases: freely decaying isotropic turbulence, incompressible turbulent channel flow at Reτ = 395, compressible turbulent channel flows at Ma = 1.5 and Reτ = 221, and Ma = 3.0 and Reτ = 556. LESs with the dynamic Smagorinsky model and the Vreman model are also performed to compare the performance of the VSS-model. The proposed model correctly recovers cubic wall behavior in the vicinity of solid boundaries in incompressible flow regime, and it has no limitation in its application to geometrically complex flows.
