Dispersion and deposition mechanisms of particles suspended in a turbulent plane Couette flow

Abstract

Inertial particle transfer in a turbulent plane Couette flow (C flow) was studied using Direct Numerical Simulation (DNS) of the flow combined with a Lagrangian particle tracking approach for particles with Stokes numbers (St) 5, 25 and 125. The particle concentration was assumed low enough, so that the simulations were done under one-way coupling condition.Our numerical simulations show that the particles suspended in a C flow (C particles) have velocities respectively smaller and larger than the carrier fluid velocities in the near-wall and core region. The C particles in comparison to the same sized particles suspended in a Poiseuille flow (P particles) with a same Reynolds number (Re), have larger fluctuating activities in the core, while the opposite was observed in the near-wall region. This fact is due to the Large Scale Structures (LSSs) existing in the core region of the C flows. The LSSs also strengthen the near-wall accumulation of C particles, so that these particles respect to the same sized P particles have more accumulation in the near-wall region. Moreover, the LSSs affect the deposition velocity of particles whereby among the P and C particles with smallest Stokes number (St=5), the C particles have larger deposition velocity while among the those ones with larger Stokes numbers (St=25,125) the opposite was the case.Finally, it was found that although the diffusional deposition mechanism for the C particles is less efficient than for the P ones, the number of deposited C particles during the time is greater than the number of deposited P particles.