Lagrangian description of the unsteady flow induced by a single pulse of a jellyfish
Lagrangian description of the unsteady flow induced by a single pulse of a jellyfish
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DOI：
10.1103/physrevfluids.4.064605
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发表时间：
2019-06-06
影响因子：
2.7
通讯作者：
Chamorro, Leonardo P.
中科院分区：
文献类型：
--
作者：
Kim, Jin-Tae;Chamorro, Leonardo P.
利用三维粒子跟踪测速仪（3D-PTV）对小水母奥雷利亚aurita的孤立脉冲引起的拉格朗日统计和对色散进行了定量和表征。拉格朗日速度分量的概率密度函数（PDF）表示更强烈的混合在径向方向上，并揭示了三个阶段占主导地位的流动加速，混合，和耗散。拉格朗日加速度方差的时间演化进一步说明了每个阶段。在混合阶段，流动具有均匀各向同性湍流的特征。此外，我们表明，一个单一的脉冲可能会引起丰富的尾流动力学的特点是对色散与超扩散的t（3）制度，由于大规模的流动不均匀性，其次是相干的t（2）-Batchelor标度，然后t（1）-布朗运动。第一种趋势发生在加速流中，而第二种动态是在混合尾流中观察到的，并且取决于初始分离。后期以流耗散为主，表现为布朗运动。在完全混合阶段的Kolmogorov微尺度得到了三个不同的方法，即，海森伯-Yaglom关系的拉格朗日加速度方差，应变张量的波动率在欧拉参考系以及Batchelor标度对色散，这表现出良好的一致性。
Lagrangian statistics and pair dispersion induced by an isolated pulse of a small jellyfish, Aurelia aurita, were quantified and characterized using 3D particle tracking velocimetry (3D-PTV). Probability density functions (PDF) of the Lagrangian velocity components indicated more intense mixing in the radial direction and revealed three stages dominated by flow acceleration, mixing, and dissipation. Time evolution of the Lagrangian acceleration variance further illustrates each phase. During the mixing phase, the flow shares characteristics of homogeneous isotropic turbulence. In addition, we show that a single pulse may induce rich wake dynamics characterized by pair dispersion with a super-diffusive t(3) regime due to large-scale flow inhomogeneity, followed by a coherent t(2)-Batchelor scaling and then t(1)-Brownian motions. The first trend occurred in the accelerated flow, whereas the second dynamic was observed in the mixed wake and depended on the initial separation. The Brownian motion was present in the late stage dominated by flow dissipation. Kolmogorov microscales during the fully mixed phase were obtained with three distinct approaches, namely, Heisenberg-Yaglom relation of the Lagrangian acceleration variance, the fluctuating rate of the strain tensor in the Eulerian frame of reference as well as the Batchelor scaling in pair dispersion, which showed good agreement.