(480e) Transition between Turbulence Regimes in Particle-Laden Channel Flows

In this talk we will present recent findings from high-resolution numerical simulations on two distinct turbulence regimes observed in particle-laden channel flows. At low mass loading, it is well established that the majority of the underlying carrier-phase turbulence manifests from classical mean-shear production. In this limit, particles tend to preferentially concentrate in high-strain regions of the flow near the channel wall. When the mass loading is order one or larger, the relative motion between the phases leads to additional sources of instabilities as a result of interphase coupling. Particles are known to spontaneously self organize into densely packed clusters. At mass loading of 10, our previous work demonstrated that fluid-phase turbulent kinetic energy (TKE) arises almost entirely from drag production past clusters, giving rise to a separate class of multiphase turbulence referred to as cluster-induced turbulence (CIT). Surprisingly, it remains to be seen how wall-bounded particle-laden flows transition from the dilute limit in which fluid-phase TKE arises from classical mean shear production, to the high-mass-loading regime dominated by drag production. In this study, we examine this transition as a function of mass loading and Stokes number. One-point and two-point statistics will be presented, and the and the separate mechanisms contributing to fluid-phase TKE energy balance will be reported.