(215g) Eulerian-Lagrangian Simulations of Bidisperse Particles in Cluster-Induced Turbulence

Particle-laden turbulent flow is an important feature of many diverse environment and industrial systems such as clouds and fluidized bed reactors. Previous work has focused on an idealized, canonical flow, cluster-induced turbulence (CIT), wherein momentum coupling between a carrier fluid and setting particles leads to turbulent-like fluctuations in various quantities of interest. Two-way coupled Eulerian-Lagrangian simulations of homogeneous CIT with monodisperse particles successfully captured, at a statistically stationary state, large-scale particle clustering, sustained turbulence in the fluid phase state, and significant uncorrelated particle motion. Statistics from these simulations, and simulations of homogeneously sheared CIT (Ireland et al., 2015) and wall bounded CIT (Capecelatro et al., 2016), have been computed.

In this work, we present extended simulations of CIT with bidisperse particle sizes. As was previously done with monodisperse CIT (Capecelatro et al., 2014 and 2015), we track the flow of energy from its generation due to drag until its dissipation due to fluid viscosity and particle collisions. The energy is tracked separately for both particle types and the fluid. As suggested by Fox (2014), we separate the energy from correlated velocity fluctuations, denoted as particle turbulent kinetic energy, and energy from uncorrelated velocity fluctuations, denoted as granular temperature. An energy balance is computed for various energy exchange terms to determine their relative importance and to elucidate the underlying physical mechanisms in bidisperse CIT. Additionally, volume fraction and velocity statistics for both particle types and the fluid are presented. These results are compared to results from Capecelatro et al. (2014 and 2015), and the consequences on closures for Reynolds Averaged stress models of multiphase flows are discussed.