Turbulence modulation by micro-particles in smooth and rough channels

Inertial micro-particles, dispersed in turbulent flows, are affected by the local dy- namics of the carrier flow field. The presence of a relative dilute loading of particles entails some relevant changes in the mean velocity field. Moreover, the roughness of the solid boundary affects both the carrier and the carried phase dynamics and their mutual interaction. The underlying physics has been exhaustively tackled in the so-called one-way coupling regime, i.e., negligible action of particles onto the fluid, whereas many aspects of the particle back-reaction have been much less investigated and are still poorly understood. Thus the research in this area remains very active. In order to understand the mutual interaction between carrier and carried phases, direct numerical simulations are particularly suitable, even at low Reynolds number. Here, particle laden flow over a complex domain is investigated at friction Reynolds number Reτ = 180. The numerical analysis is based on the Euler-Lagrange approach, taking into account the fluid-particle interaction (two-way coupling). Point forces are used to represent the back-effect of particles on the turbulence and the effect of the wall’s roughness is taken into account modeling the elastic rebound of particles onto it, instead of using a virtual rebound model. The interest is focused on the effect of micro-particles of different inertia on fluid and particle statistics in the near-wall region. In particular, turbulent and solid phase statistics are compared with those obtained for a one-way coupled flow, for the same Reynolds number in smooth and rough channel flow configurations.