On the effects of vortex trapping on the velocity statistics of tracers and heavy particle in turbulent flows
msra(2006)
摘要
The Lagrangian statistics of heavy particles and of fluid tracers transported
by a fully developed turbulent flow are investigated by means of high
resolution direct numerical simulations. The Lagrangian velocity structure
functions are measured in a time range spanning about three decades, from a
tenth of the Kolmogorov timescale up to a few large-scale eddy turnover time.
Strong evidence is obtained that fluid tracers statistics are contaminated in
the time span 1-10 times the dissipative time scale by a bottleneck effect due
to vortex trapping. This effect is found to be significantly reduced for heavy
particles which are expelled from vortices by inertia. These findings help in
clarifying the results of a recent study by H. Xu et al. Phys. Rev. Lett. 96,
024503 (2006), where differences between experimental and numerical results on
scaling properties of fluid tracers were reported.
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关键词
turbulent flow,direct numerical simulation,high resolution,structure function
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