Abstract
The development and assessment of subgrid-scale (SGS) models for large-eddy simulations of the atmospheric boundary layer is an active research area. In this study, we compare the performance of the classical Smagorinsky model, the Lagrangian-averaged scale-dependent (LASD) model, and the anisotropic minimum dissipation (AMD) model. The LASD model has been widely used in the literature for 15 years, while the AMD model was recently developed. Both the AMD and the LASD models allow three-dimensional variation of SGS coefficients and are therefore suitable to model heterogeneous flows over complex terrain or around a wind farm. We perform a one-to-one comparison of these SGS models for neutral, stable, and unstable atmospheric boundary layers. We find that the LASD and the AMD models capture the logarithmic velocity profile and the turbulence energy spectra better than the Smagorinsky model. In stable and unstable boundary-layer simulations, the AMD and LASD model results agree equally well with results from a high-resolution reference simulation. The performance analysis of the models reveals that the computational overhead of the AMD model and the LASD model compared to the Smagorinsky model is approximately 10% and 30% respectively. The LASD model has a higher computational and memory overhead because of the global filtering operations and Lagrangian tracking procedure, which can result in bottlenecks when the model is used in extensive simulations. These bottlenecks are absent in the AMD model, which makes it an attractive SGS model for large-scale simulations of turbulent boundary layers.
Highlights
Large-eddy simulation (LES) has been instrumental in the study of turbulence in the atmospheric boundary layer (ABL) (Moeng 1984; Andren et al 1994; Albertson 1996)
We find that the Lagrangian-averaged scale-dependent (LASD) and the anisotropic minimum dissipation (AMD) models capture the logarithmic velocity profile and the turbulence energy spectra better than the Smagorinsky model
We compared the performance of the Smagorinsky, the AMD (Rozema et al 2015; Abkar et al 2016; Abkar and Moin 2017), and the LASD models (Bou-Zeid et al 2005; Stoll and Porté-Agel 2006, 2008) for neutral, stable, and unstable conditions
Summary
Large-eddy simulation (LES) has been instrumental in the study of turbulence in the atmospheric boundary layer (ABL) (Moeng 1984; Andren et al 1994; Albertson 1996). In LES, large-scale eddies are resolved, and the effects of the subgrid-scale (SGS) eddies are parametrized. A significant disadvantage of the Smagorinsky model is that the SGS stresses are assumed to be universal, isotropic, and scale-invariant, which makes the model unsuitable for anisotropic flows such as ABL flows. The Germano identity relates stresses at different scales and facilitates the calculation of the Smagorinsky coefficients without ad hoc formulations. This approach assumes scale-similarity, i.e., that the model coefficients do not vary with scale. Scale-dependent models allow for more accurate modelling of SGS stresses and can capture the flow physics in wall-bounded flows better than the Smagorinsky model (Meneveau and Katz 2000)
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