Two-particle dispersion in weakly turbulent thermal convection
Two-particle dispersion in weakly turbulent thermal convection
复制标题
弱湍流热对流中的双粒子分散
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Eberhard Bodenschatz
中科院分区：
文献类型：
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作者：
Simon Schutz;Eberhard Bodenschatz
本文对Prandtl数在1附近的流体的Rayleigh-Bénard对流弱非线性区域中的粒子弥散进行了数值研究，其中存在理想的直对流卷和弱湍流之间的双稳定性，弱湍流的形式为螺旋缺陷混沌.虽然拉格朗日对统计已成为一种常用的工具，研究充分发展的湍流在高雷诺数，我们表明，质量传输的关键特征也可以在对流系统中发现，没有或弱湍流。具体来说，在短时间内，我们发现一个时间间隔的t3标度对色散，我们解释定量的平流和扩散的相互作用。很长一段时间，我们观察到粒子的扩散式分散，它变得独立于单个粒子的随机运动。传播速率依赖于时空混沌的程度。
We present results from a numerical study of particle dispersion in the weakly nonlinear regime of Rayleigh–Bénard convection of a fluid with Prandtl number around unity, where bi-stability between ideal straight convection rolls and weak turbulence in the form of spiral defect chaos exists. While Lagrangian pair statistics has become a common tool for studying fully developed turbulent flows at high Reynolds numbers, we show that key characteristics of mass transport can also be found in convection systems that show no or weak turbulence. Specifically, for short times, we find an interval of t3-scaling of pair dispersion, which we explain quantitatively with the interplay of advection and diffusion. For long times we observe diffusion-like dispersion of particles that becomes independent of the individual particles’ stochastic movements. The spreading rate is found to depend on the degree of spatio-temporal chaos.