A new subgrid characteristic length for turbulence simulations on anisotropic grids

Trias, F. X.; Gorobets, A.; Silvis, Maurits H.; Verstappen, Roel; Oliva, A.

doi:10.1063/1.5012546

Cited by 38 publications

(31 citation statements)

References 42 publications

(120 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…8 has a similar form to the Clark model [cf. 1,37,38], but with a different coefficient (i.e., 1/2 instead of 1/12) due to the difference in filtering.…”

Section: Defining the Difference Between The Two Solutions Asmentioning

confidence: 99%

Towards systematic grid selection in LES: Identifying the optimal spatial resolution by minimizing the solution sensitivity

Toosi

Larsson

2020

Computers & Fluids

View full text Add to dashboard Cite

The accuracy of a large eddy simulation (LES) is determined by the accuracy of the model used to describe the effect of unresolved scales, the numerical errors of the resolved scales, and the optimality of the length scale that separates resolved from unresolved scales (the filter-width, or the coarse-graining length scale). This paper is focused entirely on the last of these, proposing a systematic algorithm for identifying the "optimal" spatial distribution of the coarse-graining length scale and its aspect ratio. The core idea is that the "optimal" coarse-graining length scale for LES is the largest length scale for which the LES solution is minimally sensitive to it. This idea is formulated based on an error indicator that measures the sensitivity of the solution and a criterion that determines how that error indicator should vary in space and direction to minimize the overall sensitivity of the solution. The solution to this optimization problem is that the cell-integrated error indicator should be equi-distributed; a corollary is that one cannot link the accuracy in LES to quantities that are not cell-integrated, including the common belief that LES is accurate whenever 80-90% of the energy is resolved. The full method is tested on the wall-resolved LES of turbulent channel flow and the flow over a backward-facing step, with final length scale fields (or filter-width fields, or grids) that are close to what is considered "best practice" in the LES literature. Finally, the derivation of the error indicator offers an alternative explanation for the success of the dynamic procedure.

show abstract

“…8 has a similar form to the Clark model [cf. 1,37,38], but with a different coefficient (i.e., 1/2 instead of 1/12) due to the difference in filtering.…”

Section: Defining the Difference Between The Two Solutions Asmentioning

confidence: 99%

Towards systematic grid selection in LES: Identifying the optimal spatial resolution by minimizing the solution sensitivity

Toosi

Larsson

2020

Computers & Fluids

View full text Add to dashboard Cite

show abstract

“…One could also analyze the ability of the vortex-stretching-based nonlinear model to predict (coherent) flow structures, such as the Taylor-Görtler vortices that occur in spanwise-rotating planechannel flow (Dai et al 2016). Other points of interest for future studies could be adaptation of the vortex-stretching-based nonlinear model to simulate rotating turbulent flows from an inertial frame of reference, or adaptation of the subgrid characteristic length scale (see, e.g., Trias et al 2017). Finally, our results indicate that supplementing the scaled anisotropic minimum-dissipation model with the nonlinear term of the vortex-stretching-based nonlinear model is beneficial.…”

Section: Discussionmentioning

confidence: 99%

Nonlinear Subgrid-Scale Models for Large-Eddy Simulation of Rotating Turbulent Flows

Silvis

Verstappen

2019

Direct and Large-Eddy Simulation XI

Self Cite

View full text Add to dashboard Cite

Rotating turbulent flows form a challenging test case for large-eddy simulation (LES). We, therefore, propose and validate a new subgrid-scale (SGS) model for such flows. The proposed SGS model consists of a dissipative eddy viscosity term as well as a nondissipative term that is nonlinear in the rate-of-strain and rate-of-rotation tensors. The two corresponding model coefficients are a function of the vortex stretching magnitude. Therefore, the model is consistent with many physical and mathematical properties of the Navier-Stokes equations and turbulent stresses, and is easy to implement. We determine the two model constants using a nondynamic procedure that takes into account the interaction between the model terms. Using detailed direct numerical simulations (DNSs) and LESs of rotating decaying turbulence and spanwise-rotating plane-channel flow, we reveal that the two model terms respectively account for dissipation and backscatter of energy, and that the nonlinear term improves predictions of the Reynolds stress anisotropy near solid walls. We also show that the new SGS model provides good predictions of rotating decaying turbulence and leads to outstanding predictions of spanwise-rotating plane-channel flow over a large range of rotation rates for both fine and coarse grid resolutions. Moreover, the new nonlinear model performs as well as the dynamic Smagorinsky and scaled anisotropic minimum-dissipation models in LESs of rotating decaying turbulence and outperforms these models in LESs of spanwise-rotating plane-channel flow, without requiring (dynamic) adaptation or near-wall damping of the model constants.

show abstract

“…On the other hand, anisotropic filter lengths have been used in conjunction with anisotropic subgrid scale models (Bardina et al 1980(Bardina et al , 1983aAbbà et al 2017). See Trias et al (2017) and references therein, for a review of different length scales accounting for the anisotropy of the flow. Although successfully employed, these anisotropic filter sizes have been defined in a rather heuristic way.…”

Section: First-order Modellingmentioning

confidence: 99%

General formalism for a reduced description and modelling of momentum and energy transfer in turbulence

2019

View full text Add to dashboard Cite

Based on hierarchies of filter lengths, the large eddy decomposition and the related subgrid stresses are recognized to represent generalized central moments for the study and modelling of the different modes composing turbulence. In particular, the subgrid stresses and the subgrid dissipation are shown to be alternative observables for quantitatively assessing the scale-dependent properties of momentum flux (subgrid stresses) and the energy exchange between the large and small scales (subgrid dissipation). In this work we present a theoretical framework for the study of the subgrid stress and dissipation. Starting from an alternative decomposition of the turbulent stresses, a new formalism for their approximation and understanding is proposed which is based on a tensorial turbulent viscosity. The derived formalism highlights that every decomposition of the turbulent stresses is naturally approximated by a general form of turbulent viscosity tensor based on velocity increments which is then recognized to be a peculiar property of small-scale stresses in turbulence. The analysis in a turbulent channel shows the rich physics of the small-scale stresses which is unveiled by the tensorial formalism and usually missed in scalar approaches. To further exploit the formalism, we also show how it can be used to derive new modelling approaches. The proposed models are based on the second- and third-order inertial properties of the grid element. The basic idea is that the structure of the integration volume for filtering (either implicit or explicit) impacts the anisotropy and inhomogeneity of the filtered-out motions and, hence, this information could be leveraged to improve the prediction of the main unknown features of small-scale turbulence. The formalism provides also a rigorous definition of characteristic lengths for the turbulent stresses, which can be computed in every type of computational elements, thus overcoming the rather elusive definition of filter length commonly employed in more classical models. A preliminary analysis in a turbulent channel shows reasonable results. In order to solve numerical stability issues, a tensorial dynamic procedure for the evolution of the model constants is also developed. The generality of the procedure is such that it can be employed also in more conventional closures.

show abstract

A new subgrid characteristic length for turbulence simulations on anisotropic grids

Cited by 38 publications

References 42 publications

Towards systematic grid selection in LES: Identifying the optimal spatial resolution by minimizing the solution sensitivity

Towards systematic grid selection in LES: Identifying the optimal spatial resolution by minimizing the solution sensitivity

Nonlinear Subgrid-Scale Models for Large-Eddy Simulation of Rotating Turbulent Flows

General formalism for a reduced description and modelling of momentum and energy transfer in turbulence

Contact Info

Product

Resources

About