Motivated by the large-scale transport of particles in environmental flows and the need to use large-eddy simulations (LES) with coarse (yet suitably resolved) grids, this study examines the impact of LES filtering and subgrid-scale (SGS) turbulence on the transport of particles in a boundary layer flow. Spherical and inertial particles subjected to gravity are considered, and the Lagrangian tracking of their trajectories is performed across three flows: Direct Numerical Simulations (DNS), a priori LES, and a priori LES enhanced with SGS turbulence. The SGS turbulence is modeled with an approximate deconvolution model based on an elliptical differential filter, which was tested here for its performance in anisotropic boundary layer flows. Considering different particle inertias, a comparative analysis of particle and flow phase statistics is performed, and the impact of SGS turbulence is discussed. In the fluid phase, results indicate that the inclusion of SGS turbulence led to an overall improvement of the statistics in relation to DNS. Such improvements were driven by the energization of the turbulence scales in LES, which was characterized by increased intermittency of the velocity gradients and fluctuations. In the particle phase, the impact of SGS turbulence is shown to be sensitive to particle inertia, with lighter particles being the most affected. The inclusion of SGS turbulence led to larger particle velocity fluctuations and an enhancement of their settling velocity, leading to a reduction in their streamwise spreading across the boundary layer.
Santos et al. (Fri,) studied this question.