In order to study the effects of turbulence sub-grid-scale (SGS) fluctuation on particle Lagrangian motion in turbulent flows, a dynamic random walk (DRW) SGS coupling model based on an Eulerian-Lagrangian approach was developed. The advantage of the new model is that the Gaussian statistical distribution and local isotropic properties of turbulence SGS fluctuation can be parameterized by Germano’s (1991) Eulerian dynamic procedure. Using the present model, large eddy simulation (LES) was performed for downward channel flow at a Reynolds number of 180, as in the direct numerical simulation (DNS) done by Rouson & Eaton in 1997. Through a comparing of the statistical properties of particle diffusion with DNS, the capabilities and limitations of the present DRW SGS model were verified. Moreover, it was found that turbulence SGS fluctuation was strongly associated with particle motion, because preferred particles were affected by the preferred length scale of the eddy structure around. It was also found that turbulence SGS fluctuations are indispensable in calculating particles’ Lagrangian trajectories in LES even when the particle Stokes number is high.

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