B-244 乱流相対拡散における粒子対の運動の分類

概要

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We investigates the dynamics of particle pairs in two-dimensional free convection turbulence (FC2D) by direct numerical simulation. In entropy cascade region, the growth of pair separation γ is expected <γ^2(t)> α t^5 according to the Bolgiano-Obukhov scaling. We obtained the results supporting this scaling with exit-time statistics. We show that the dynamics of particle pairs are classified into two types : stretching along fine coherent structures of T-Vorticity (S-region) and trapping by eddies associated with the scales of the order of pair separations (T-region), and the crossover time separating S- and T-Region T^E_<div>(ρ) follows a scaling law T^E_<div>(ρ)α(ρ-1)^<-0.57>, where ρ is one of parameters in exit-time statistics. Furthermore, our results also suggest that the time evolution of pair separations in the T-region is described by the Richardson's diffusion equation.
日本流体力学会の論文
2003-07-28