A New Realizable Subgrid-Scale Stress Model for Large Eddy Simulation of Neutral Atmospheric Boundary Layer

摘要

Dynamic Smagorinsky model (DSM) is commonly used to model the subgrid scale (SGS) stress tensor in large eddy simulations (LES). However, the DSM yields large fluctuations of the Smagorinsky constant and can make the simulations unstable. To avoid the stability problems, averaging along homogeneous directions or artificial clipping of the constant is often employed in simulations. This reveals the need for the development of SGS models that can be used in simulations without numerical modifications. In the current study, the performance of a linear dynamic SGS model derived using stochastic analysis is investigated. Turbulent channel flow is chosen as the test case to evaluate the model. The computations were numerically stable without averaging or clipping of the Smagorinsky constant. The results also showed good agreement with benchmark direct numerical simulation data. The validated model was applied to perform neutral atmospheric boundary layer simulations. The predicted mean wind speed showed good agreement with the log law while the peaks of the Reynolds normal stresses were within the range of values observed in the literature. However, the model predicted a lower value of the modeled Reynolds shear stress in the surface layer. Empirical modifications in the surface layer were considered to improve the predictions. Future work on accurate prediction of the Reynolds shear stress in the surface layer without any modifications is outlined.