Multiscale influences of particles in high-Re wall turbulence

The two-way coupling between inertial particles and wall-bounded turbulence has been the subject of decades of theoretical, experimental, and numerical research, and has analyzed phenomena including coherent structure modulation, particle clustering, and turbophoresis. For the many studies using DNS, however, flow Reynolds numbers have been generally small (friction Reynolds numbers less than, say, 300), falling well beneath the onset of asymptotic outer scale behavior (friction Reynolds numbers around 1000). In this study, we use DNS up to friction Reynolds numbers of 5200 coupled with Lagrangian point particles to focus on particle-turbulence interaction in the context of high-Reynolds number wall turbulence. The goal is to better understand initial particle behavior in the presence of a significant range of flow scales. Multiple mechanisms of particle modulation of the turbulent flow are found, where even small particle Stokes numbers can influence outer-scale motions by modulating inner-scale motions and regeneration cycles, and in all cases, the influence of the particles is broadband, meaning that the entire range of flow scales feels the influence of particles whose size are smaller than the Kolmogorov scales.