On fluid-particle and particle-particle interactions in gas-solid turbulent channel flow

Large-Eddy Simulation (LES) and Discrete Particle Simulation (DPS) are used to highlight effects of fluid-particle and particle-particle interactions on dispersed-phase transport in fully-developed turbulent channel flow. A range of particle Stokes numbers in the simulations are considered that lead to strong changes in particle response. In the absence of inter-particle collisions, the calculations illustrate the characteristic build-up of particles in the near-wall region. While mean shear in the carrier and dispersed phase velocities is an important effect in wall-bounded flows, LES/DPS results show that the particle velocity fluctuations in the wall-normal direction are controlled primarily by the drag force and in equilibrium with the corresponding components of the fluid-particle velocity correlation. Inter-particle collisions provide a redistribution mechanism that reduces the strong anisotropy of the particle velocity fluctuations and substantially elevates cross-stream transport. Spatial properties of the particle velocity field are examined using two-point correlations. The correlation functions are discontinuous at the origin and are consistent with a partitioning of the particle velocity by inertia into a spatially-correlated contribution and random component that is not correlated in space. Perspectives and implications of these findings are also discussed.