チャネル流の乱流縞剛健性に関する質点粒子ストークス数への依存性

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  • Point-particle Stokes number dependence of robustness of turbulent stripe in channel flow

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<p>Direct numerical simulations are performed in plane Poiseuille flows with point-particles for varying density ratio of particle to fluid, or Stokes number. The purpose of our study is to understand subcritical transition in particle-laden flows. We investigated the effect of particle-fluid interactions on the robustness of intermittent localized turbulence, so-called turbulent stripe, in two-way coupling simulations. The stripe was found to disappear due to heavier particles with a density ratio over 4000, while it sustained with light particles, or small Stokes number. The particle-fluid interactions act favorably near the walls, but adversely in the channel central region with respect to the streamwise direction for all cases. The interaction force significantly is exerted in the case of heavier particle, or large Stokes number. In this paper, we also showed the instantaneous momentum transfer of the streamwise Reynolds normal stress. The production term gradually decreases with the increasing Stokes number. Furthermore, we found that the energy exchange due to particle-fluid interactions is from particle to fluid near the wall and is reversed in the channel central region. For larger-Stokes-number particles, the transports occur actively at each height during laminarization process.</p>

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