Dynamic self-organization in particle-laden turbulent channel flow

This chapter examines dynamic self-organization in particle-laden turbulent channel flow. Many flows of relevance to large-scale chemical processing involve solid catalyst particles at significant concentrations embedded in a carrying gas-flow. Control over the spatial distribution of these particles, especially its homogeneity, is essential in order to provide a chemical processing that is as complete and uniform as possible, that is consistent with modern environmental requirements and that does not constitute a strong safety hazard. This chapter analyzes the fundamental aspects turbulent riser-flow which contains large numbers of interacting particles. Particle-particle as well as particle-fluid interactions are also included in the chapter. These interactions and the flow-forcing are the source for the dynamic formation and destruction of large-scale coherent particle swarms in the flow. The basic scenario of this self-organization is established, and the dominant aspects of the resulting turbulence modulation are investigated. 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 is found that neglecting particle-particle interactions leads to an unphysical modulated flow.