Dynamic self-organization in particle-laden turbulent channel flow

We study fundamental aspects of turbulent riser-flow which contains large numbers of interacting particles. We include particle-particle as well as particle-fluid interactions. These interactions and the flow-forcing are the source for the dynamic formation and destruction of large-scale coherent particle swarms in the flow. We establish the basic scenario of this self-organization and investigate the dominant aspects of the resulting turbulence modulation. Large-eddy simulations with different subgrid models, and large numbers of particles at a significant volume fraction and realistic mass load ratio, indicate the development of a thinner boundary layer and an accumulation of particles near the walls. At an average volume fraction of ≈ 1.5% it was found that neglecting particleparticle interactions leads to an unphysical modulated flow.