Lagrangian conditional statistics, acceleration and local relative motion in numerically simulated isotropic turbulence

摘要: Lagrangian statistics of fluid-particle velocity and acceleration conditioned on fluctuations dissipation, enstrophy pseudo-dissipation representing different characteristics local relative motion are extracted from a direct numerical simulation database stationary (forced) homogeneous isotropic turbulence. The grid resolution in the simulations is up to 2048 3 , Taylor-scale Reynolds number ranges about 40 650, where small-scale intermittency Eulerian flow field well developed. A key joint statistic conditioning variables dissipation-enstrophy cross-correlation, which asymmetric, but becomes less so at high number. Conditional autocorrelations consistent with rapid changes fluid particles moving regions large gradients. Examination upon enstrophy, especially coordinate frame vorticity vector, centripetal suggests presence vortex-trapping effects persist for several Kolmogorov time scales. Further results velocity-acceleration also presented help characterize detail properties stochastic process velocity, pseudo-dissipation. Together recent work conditional Reynolds-number dependence basic quantities, present directly useful development new model formulated account as described companion paper.