Characterizing vortex tangle properties in steady-state He II counterflow using particle tracking velocimetry
Characterizing vortex tangle properties in steady-state He II counterflow using particle tracking velocimetry
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DOI：
10.1103/physrevfluids.4.023301
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发表时间：
2019-02-07
影响因子：
2.7
通讯作者：
Guo, Wei
中科院分区：
文献类型：
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作者：
Mastracci, Brian;Guo, Wei
从历史上看，一直很少有信心在粒子跟踪测速（PTV）作为一种工具，使定量测量热逆流在He II，因为示踪粒子运动是复杂的正常流体，超流体，和量子化的涡线，或其组合的影响。最近，我们介绍了一个方案，用于区分被捕获在旋涡（G1）上的颗粒和被正常流体（G2）夹带的颗粒。在本文中，我们应用这个计划来证明PTV的效用，在He II逆流的涡旋动力学的定量测量。我们估计l，平均涡线间距，使用G2速度数据，和c（2），一个参数有关的平均曲率半径的涡旋和能量耗散的量子湍流，使用G1速度数据。我们发现，这两个估计显示出良好的协议与现有的测量，使用传统的实验方法。这是特别重要的，因为这些参数可能在空间中变化，并且PTV提供了空间分辨率的优势。我们还表明，在横向粒子速度概率密度函数（PDF）和重联的涡线上G1粒子被困的幂律尾之间的直接联系。
Historically, there has been little faith in particle tracking velocimetry (PTV) as a tool to make quantitative measurements of thermal counterflow in He II, since tracer particle motion is complicated by influences from the normal fluid, superfluid, and quantized vortex lines, or a combination thereof. Recently, we introduced a scheme for differentiating particles trapped on vortices (G1) from particles entrained by the normal fluid (G2). In this paper, we apply this scheme to demonstrate the utility of PTV for quantitative measurements of vortex dynamics in He II counterflow. We estimate l, the mean vortex line spacing, using G2 velocity data, and c(2), a parameter related to the mean curvature radius of vortices and energy dissipation in quantum turbulence, using G1 velocity data. We find that both estimations show good agreement with existing measurements that were obtained using traditional experimental methods. This is of particular consequence since these parameters likely vary in space, and PTV offers the advantage of spatial resolution. We also show a direct link between power-law tails in transverse particle velocity probability density functions (PDFs) and reconnection of vortex lines on which G1 particles are trapped.