Lagrangian diffusion properties of a free shear turbulent jet
Lagrangian diffusion properties of a free shear turbulent jet
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DOI：
10.1017/jfm.2021.325
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发表时间：
2021-02
影响因子：
3.7
通讯作者：
B. Viggiano;T. Basset;S. Solovitz;T. Barois;M. Gibert;N. Mordant;L. Chevillard;R. Volk;M. Bourgoin;R. B. Cal
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作者：
B. Viggiano;T. Basset;S. Solovitz;T. Barois;M. Gibert;N. Mordant;L. Chevillard;R. Volk;M. Bourgoin;R. B. Cal
摘要对轴对称湍流水射流进行了拉格朗日实验研究，研究了射流流场的各向异性和非均匀性。测量是在拉格朗日探索模块，二十面体装置，以促进三个相机的光学访问。立体粒子跟踪测速仪的结果在三个分量的跟踪的位置，速度和加速度的示踪剂粒子内的垂直取向的射流与泰勒为基础的雷诺数${\textit {Re}}_\lambda \simeq 230$。在下游15直径至45直径的7个位置进行分析。首先进行欧拉分析，以获得射流和相关尺度的临界参数，即柯尔莫哥洛夫和大（积分）尺度以及能量耗散率。然后，按照由Batchelor（J. Fluid Mech.，第3卷，1957年，第100页。67-80），其目的是将泰勒的湍流扩散的定常拉格朗日理论扩展到自相似流的情况。典型的拉格朗日缩放参数的发展射流的函数的演变进行了探讨，结果表明所提出的stationarisation验证。通用的标度常数C_0 $（拉格朗日二阶结构函数），以及欧拉和拉格朗日积分时间尺度，在这方面进行了讨论。发现常数$C_0$在喷嘴下游的30直径内收敛到一个常数值（约为$C_0 = 3$）。最后，有限颗粒尺寸效应的发生进行了研究，通过考虑加速度依赖量。
Abstract A Lagrangian experimental study of an axisymmetric turbulent water jet is performed to investigate the highly anisotropic and inhomogeneous flow field. Measurements are conducted within a Lagrangian exploration module, an icosahedron apparatus, to facilitate optical access of three cameras. Stereoscopic particle tracking velocimetry results in three-component tracks of position, velocity and acceleration of the tracer particles within the vertically oriented jet with a Taylor-based Reynolds number ${\textit {Re}}_\lambda \simeq 230$. Analysis is performed at seven locations from 15 diameters up to 45 diameters downstream. Eulerian analysis is first carried out to obtain critical parameters of the jet and relevant scales, namely the Kolmogorov and large (integral) scales as well as the energy dissipation rate. Lagrangian statistical analysis is then performed on velocity components stationarised following methods inspired by Batchelor (J. Fluid Mech., vol. 3, 1957, pp. 67–80), which aim to extend stationary Lagrangian theory of turbulent diffusion by Taylor to the case of self-similar flows. The evolution of typical Lagrangian scaling parameters as a function of the developing jet is explored and results show validation of the proposed stationarisation. The universal scaling constant $C_0$ (for the Lagrangian second-order structure function), as well as Eulerian and Lagrangian integral time scales, are discussed in this context. Constant $C_0$ is found to converge to a constant value (of the order of $C_0 = 3$) within 30 diameters downstream of the nozzle. Finally, the occurrence of finite particle size effects is investigated through consideration of acceleration-dependent quantities.