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The problem of an accurate Eulerian-Lagrangian modeling of inertial particledispersion in Large Eddy Simulation (LES) of turbulent wall-bounded flows isaddressed. We run Direct Numerical Simulation (DNS) for turbulent channel flowat shear Reynolds numbers equal to 150 and 300 and corresponding a-priori anda-posteriori LES on differently coarse grids. We then tracked swarms ofdifferent inertia particles and we examined the influence of filtering and ofSub-Grid Scale (SGS) modeling for the fluid phase on particle velocity andconcentration statistics. We also focused on how particle preferentialsegregation is predicted by LES. Results show that even ``well-resolved'' LESis unable to reproduce the physics as demonstrated by DNS, both for particleaccumulation at the wall and for particle preferential segregation. Inaccurateprediction is observed for the entire range of particles considered in thisstudy, even when the particle response time is much larger than the flowtimescales not resolved in LES. Both a-priori and a-posteriori tests indicatethat recovering the level of fluid and particle velocity fluctuations is notenough to have accurate prediction of near-wall accumulation and localsegregation. This may suggest that reintroducing the correct amount ofhigher-order moments of the velocity fluctuations is also a key point for SGSclosure models for the particle equation. Another important issue is thepresence of possible flow Reynolds number effects on particle dispersion. Ourresults show that, in small Reynolds number turbulence and in the case of heavyparticles, the shear fluid velocity is a suitable scaling parameter to quantifythese effects.

Some issues concerning Large-Eddy Simulation of inertial particle dispersion in turbulent bounded flows