(562c) Numerical Simulation of Sheared, Gas-Particle, Cluster-Induced Turbulence
Recent studies have shown that momentum coupling between a gas carrier phase and finite-sized settling particles leads to the production of gas-phase kinetic energy fluctuations (Capecelatro, Desjardins, & Fox 2014; Capecelatro, Desjardins, & Fox 2015). The resulting class of flows is referred to as cluster-induced turbulence (CIT), and is expected to play a role in a number of industrial and environmental processes, including fluidized bed reactions, spray combustion, and cloud formation. CIT simulations performed for the simple case of a particle falling in an initially quiescent flow have exhibited large-scale particle clustering and turbulent-like gas-phase velocity fluctuations.
Our simulations add an additional complexity to the above studies by imposing a homogeneous background shear to the gas phase. We first study the interaction between the imposed shear and the gas-phase velocity fluctuations induced by the particles. In single-phase homogeneous turbulent shear flows (HTSF), the production always exceeds the dissipation, leading to an unbounded growth of the turbulent kinetic energy with time. We explore the similarities and differences between sheared CIT and HTSF, and assess the relevant particle and fluid parameters controlling the evolution of the gas-phase turbulent kinetic energy in sheared CIT. We also compare the particle-phase statistics in sheared CIT to those from recent studies of particle-laden HTSF (Sukheswalla & Collins 2015), unsheared CIT (Capecelatro, Desjardins, & Fox 2014; Capecelatro, Desjardins, & Fox 2015), and wall-bounded CIT (Capecelatro & Desjardins 2015). We use these data to understand the physical mechanisms affecting the gas and particle phases in each of these cases, and to develop models for the dynamics of both phases.