Flow Modulation by Finite Size Neutrally Buoyant Particles in a Turbulent Channel Flow

Abstract

A fully mesoscopic, multiplerelaxationtime (MRT) lattice Boltzmann method (LBM) is developed to perform particleresolved direct numerical simulation (DNS) of wallbounded turbulent particleladen flows. The fluid–solid particle interfaces are treated as sharp interfaces with noslip and nopenetration conditions. The force and torque acting on a solid particle are computed by a local Galileaninvariant momentum exchange method. The first objective of the paper is to demonstrate that the approach yields accurate results for both singlephase and particleladen turbulent channel flows, by comparing the LBM results to the published benchmark results and a fullmacroscopic finitedifference directforcing (FDDF) approach. The second objective is to study turbulence modulations by finitesize solid particles in a turbulent channel flow and to demonstrate the effects of particle size. Neutrally buoyant particles with diameters 10% and 5% the channel width and a volume fraction of about 7% are considered. We found that the mean flow speed was reduced due to the presence of the solid particles, but the local phaseaveraged flow dissipation was increased. The effects of finite particle size are reflected in the level and location of flow modulation, as well as in the volume fraction distribution and particle slip velocity near the wall.