Improving Large-Eddy Simulation of Neutral Atmospheric Boundary Layer Flow on Nested Grids

Abstract:

Increasing computational power has enabled grid resolutions that support large-eddy simulation (LES) of the atmospheric boundary layer (ABL). These simulations often use nested grids, which allow detailed simulation of a small subdomain of interest through a series of grid refinements. LES generates errors at grid refinement interfaces, such as resolved energy accumulation, that may compromise solution accuracy. In this talk, I will discuss using the LES turbulence closure to mitigate errors associated with the use of LES on nested grids for a neutral ABL simulation. Specifically, I compare explicit filtering of the advection term and the mixed model to implicit filtering and the eddy viscosity model. Explicitly filtering the advection term allows both mass and momentum to be conserved across grid refinement interfaces. The mixed model reduces unphysical perturbations due to wave reflection. These results demonstrate the strong effect of the turbulence closure on nested grid LES solutions.