Bec J, Biferale L, Cencini M, Lanotte A, Musacchio S, Toschi F
CNRS UMR6202, Observatoire de la Côte d'Azur, BP4229, 06304 Nice Cedex 4, France.
Phys Rev Lett. 2007 Feb 23;98(8):084502. doi: 10.1103/PhysRevLett.98.084502. Epub 2007 Feb 21.
Spatial distributions of heavy particles suspended in an incompressible isotropic and homogeneous turbulent flow are investigated by means of high resolution direct numerical simulations. In the dissipative range, it is shown that particles form fractal clusters with properties independent of the Reynolds number. Clustering is there optimal when the particle response time is of the order of the Kolmogorov time scale tau(eta). In the inertial range, the particle distribution is no longer scale invariant. It is, however, shown that deviations from uniformity depend on a rescaled contraction rate, which is different from the local Stokes number given by dimensional analysis. Particle distribution is characterized by voids spanning all scales of the turbulent flow; their signature in the coarse-grained mass probability distribution is an algebraic behavior at small densities.
通过高分辨率直接数值模拟研究了悬浮在不可压缩各向同性均匀湍流中的重颗粒的空间分布。在耗散范围内，结果表明颗粒形成了具有与雷诺数无关特性的分形簇。当颗粒响应时间为科尔莫戈罗夫时间尺度τ(η)量级时，聚类在此处达到最优。在惯性范围内，颗粒分布不再是尺度不变的。然而，结果表明与均匀性的偏差取决于一个重新标度的收缩率，该收缩率不同于通过量纲分析给出的局部斯托克斯数。颗粒分布的特征是存在跨越湍流所有尺度的空隙；它们在粗粒化质量概率分布中的特征是在小密度下呈现代数行为。
