Abstract
A study is conducted to identify advantages and limitations of existing large-eddy simulation (LES) closures for the subgrid-scale (SGS) kinetic energy using a database of direct numerical simulations (DNS). The analysis is conducted for both reacting and nonreacting flows, different turbulence conditions, and various filter sizes. A model, based on dissipation and diffusion of momentum (LD-D model), is proposed in this paper based on the observed behavior of four existing models. Our model shows the best overall agreements with DNS statistics. Two main investigations are conducted for both reacting and nonreacting flows: (i) an investigation on the robustness of the model constants, showing that commonly used constants lead to a severe underestimation of the SGS kinetic energy and enlightening their dependence on Reynolds number and filter size; and (ii) an investigation on the statistical behavior of the SGS closures, which suggests that the dissipation of momentum is the key parameter to be considered in such closures and that dilatation effect is important and must be captured correctly in reacting flows. Additional properties of SGS kinetic energy modeling are identified and discussed.
Highlights
Turbulence is ubiquitous in various applications from aerodynamics, environment, and astrophysics to energy production
As for the relative behavior between the Smallest resolved velocity (SRV) and Colin’s models discussed for nonreacting flows in the previous paragraph, the poor predictions observed in reacting flows for Bardina’s model is explainable by the noise introduced by the higher order terms, which are truncated in the localized diffusion-dissipation (LD-D) model
An additional model, based on dissipation and diffusion of the kinetic energy [LD-D model, Eq (9)], was developed from the observed behavior of the other models for nonreacting flows, and this model is shown to outperform all other models for reacting flows for all the conditions and filter sizes explored in this study
Summary
Turbulence is ubiquitous in various applications from aerodynamics, environment, and astrophysics to energy production. Over the past few decades, large eddy simulation (LES) has become a widely used tool to simulate turbulent flows thanks to the increase in computational power. Scales down to are resolved, while the residual part requires some form of modeling. The residual scales are often referred to as subgrid scales (SGS) when the filter size is assumed to be the size of a mesh element. This is not always the case in a LES, this distinction is unnecessary for the purposes of this paper, and the terms unresolved and subgrid will be used indistinctly on
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