Robustness of turbulent stripes in particle-laden channel flows

It is known that intermittent localized turbulence, so-called turbulent stripes, sustains in the form of oblique bands in subcritical transitional regime of channel flows. The pattern is formed and accompanied by secondary flows along the localized turbulence. In particle-laden turbulent flows, turbulent intensity can be enhanced or suppressed by particles. However, the effect of the particles on the turbulent stripes in subcritical transitional regime is still unknown. In this paper, we investigated the particle distributions with respect to the turbulent stripes in one-way coupling simulations and studied the effect of particle-fluid interactions on the robustness of the stripes in two-way coupling simulations. In one-way coupling, the turbulent stripe provides a cluster of heavier, or large-Stokes-number, particles in a form of oblique band similar to the stripe, in the wall-parallel direction. Furthermore, heavier particles accumulate near the wall even without gravity. In two-way coupling, the stripes tend to be broken for heavier particles. The stability of the pattern also depends on the particle volume fraction. For higher volume fraction of particle, particles have a significant effect on the sustenance of the stripes. In such a case, the particle-fluid interactions exhibit the force that accelerates the fluid near the wall. The turbulent kinetic energies of large-scale flow and fine-scale eddies are attenuated by heavier particles. Different wave-number scaled structures were generated and disappeared as a laminarization process.