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首页> 外文期刊>Journal of Fluid Mechanics >Experimental study on dominant vortex structures in near-wall region of turbulent boundary layer based on tomographic particle image velocimetry
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Experimental study on dominant vortex structures in near-wall region of turbulent boundary layer based on tomographic particle image velocimetry

机译：基于断层粒子图像速度测速法的湍流边界层近壁区域主导涡流结构的实验研究

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摘要

Vortex structures are very popular research objects in turbulent boundary layers (TBLs) because of their prime importance in turbulence modelling. This work performs a tomographic particle image velocimetry measurement on the near-wall region ( $y ) of TBLs at three Reynolds numbers $Re_{unicode[STIX]{x1D70F}}=1238$ , 2286 and 3081. The main attention is paid to the wall-normal evolution of the vortex geometries and topologies. The vortex is identified with swirl strength ( $unicode[STIX]{x1D706}_{ci}$ ), and its orientation is recognized by using the real eigenvector of the velocity gradient tensor. The vortex inclination angles in the streamwise-wall-normal plane and in the streamwise-spanwise plane as functions of wall-normal positions are investigated, which provide useful information to speculate on the three-dimensional shape of the vortex tubes in a TBL. The difference between the orientations of vorticity and swirl is discussed and their inherent relationship is revealed based on the governing equation of vorticity. Linear stochastic estimation (LSE) is further deployed to directly extract three-dimensional vortex models. The LSE velocity fields for ejection events happening at different wall-normal positions shed light on the evolution of the topologies for the vortices dominating ejection events. LSE based on a centred prograde spanwise vortex provides a typical packet model, which indicates that the population density of the packets in a TBL is large enough to leave footprints in conditionally averaged flow fields. This work should help to settle the severe debate on the existence of packet structures and also lays some foundation for the TBL model theory.
机译：由于其在湍流建模中的主要重要性，涡流结构是非常流行的湍流边界层（TBL）的研究对象。这项工作在TBLS的近壁区域（$ Y）在三个雷诺数$ RE _ { Unicode [STIX] {X1D70F}} {x1d70f}} = 1238 $，2286和3081。主要注意力涡旋几何和拓扑的墙壁正常演变。涡旋用旋流强度识别（$ Unicode [stix] {x1d706} _ {ci} $），并且通过使用速度梯度张量的真正特征向量来识别其方向。研究了流动壁 - 正常平面中的涡流倾斜角度，以及作为壁正常位置的函数的流动翼展平面中的涡旋倾斜角度，其提供有用的信息来推测TBL中涡流的三维形状。讨论了涡旋和旋流方向之间的差异，并基于涡流的控制方程揭示了其固有关系。进一步部署线性随机估计（LSE）以直接提取三维涡流模型。在不同壁正常位置发生在不同壁正常位置的喷射事件的LSE速度场在主导喷射事件的扭曲的拓扑的演变上。基于居中的翼展涡流的LSE提供了一种典型的分组模型，这表明TBL中的分组的人口密度足够大，以便在条件平均流场中留下足迹。这项工作应有助于解决关于存在包结构的严重争论，并为TBL模型理论奠定了一些基础。

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  • 来源
    《Journal of Fluid Mechanics》 |2019年第2019期|共29页
  • 作者

    Wang Chengyue; Gao Qi; Wang Jinjun; Wang Biao; Pan Chong;

  • 作者单位

    Sun Yat Sen Univ Sino French Inst Nucl Engn &

    Technol Zhuhai 519000 Peoples R China;

    Zhejiang Univ Sch Aeronaut &

    Astronaut Hangzhou 310027 Zhejiang Peoples R China;

    Beihang Univ Fluid Mech Key Lab Educ Minist Beijing 100191 Peoples R China;

    Sun Yat Sen Univ Sino French Inst Nucl Engn &

    Technol Zhuhai 519000 Peoples R China;

    Beihang Univ Fluid Mech Key Lab Educ Minist Beijing 100191 Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 流体力学;
  • 关键词

    turbulent boundary layers;

    机译：湍流边界层;

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