Tetrahedron deformation and alignment of perceived vorticity and strain in a turbulent flow
Tetrahedron deformation and alignment of perceived vorticity and strain in a turbulent flow
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DOI：
10.1063/1.4795547
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发表时间：
2012-04
影响因子：
4.6
通讯作者：
A. Pumir;E. Bodenschatz;Haitao Xu
中科院分区：
文献类型：
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作者：
A. Pumir;E. Bodenschatz;Haitao Xu
我们通过与尺度相关的感知速度梯度张量来描述湍流的结构和动力学，并由以下四个示踪剂（即流体粒子）支持，这些示踪剂最初形成正四面体。我们报告了冯卡门旋流水流实验和不可压缩纳维-斯托克斯方程数值模拟的结果。我们分析了大小为 r0 的初始正四面体从耗散尺度到积分尺度的应变张量和涡度感知速率的统计和动态。正如真实速度梯度一样，在任何时刻，感知的涡度也优先与感知的应变率的中间特征向量对齐。然而，在给定时间 t = 0 固定的感知应变本征帧速率中，感知涡量随时间演变，以便与 t = 0 时的最强本征方向对齐。这也适用于真实速度梯度。较高雷诺数的实验数据表明......
We describe the structure and dynamics of turbulence by the scale-dependent perceived velocity gradient tensor as supported by following four tracers, i.e., fluid particles, that initially form a regular tetrahedron. We report results from experiments in a von Karman swirling water flow and from numerical simulations of the incompressible Navier-Stokes equation. We analyze the statistics and the dynamics of the perceived rate of strain tensor and vorticity for initially regular tetrahedron of size r0 from the dissipative to the integral scale. Just as for the true velocity gradient, at any instant, the perceived vorticity is also preferentially aligned with the intermediate eigenvector of the perceived rate of strain. However, in the perceived rate of strain eigenframe fixed at a given time t = 0, the perceived vorticity evolves in time such as to align with the strongest eigendirection at t = 0. This also applies to the true velocity gradient. The experimental data at the higher Reynolds number suggests ...