Identification of the energy contributions associated with wall-attached eddies and very-large-scale motions in the near-neutral atmospheric surface layer through wind LiDAR measurements
Identification of the energy contributions associated with wall-attached eddies and very-large-scale motions in the near-neutral atmospheric surface layer through wind LiDAR measurements
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DOI：
10.1017/jfm.2022.1080
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发表时间：
2022-08
影响因子：
3.7
通讯作者：
M. Puccioni;M. Calaf;E. Pardyjak;S. Hoch;T. Morrison;A. Perelet;G. Iungo
中科院分区：
文献类型：
--
作者：
M. Puccioni;M. Calaf;E. Pardyjak;S. Hoch;T. Morrison;A. Perelet;G. Iungo
**摘要** 近期关于壁面约束流动的研究证实了壁面附着涡与超大尺度运动（VLSMs）共存的现象，壁面附着涡的统计特征可通过汤森（Townsend）的附着涡假设（AEH）进行预测。此外，研究表明，当外流尺度与粘性尺度显著分离时，对数层内壁面附着涡的存在与流向速度能谱中逆幂律区域的出现相关。在本研究中，利用风激光探测与测距技术对近中性大气表层进行探测，以研究极高雷诺数边界层中壁面附着涡和VLSMs对流向速度能量的贡献。通过分析流向速度的能量谱和线性相干谱（LCS），来确定与不同类型涡相关的谱边界。受AEH启发，构建了与壁面附着涡相关的LCS解析模型。实验结果表明，通过能谱分析来识别壁面附着涡的能量贡献，会导致对相关谱范围、达到的最大高度以及湍流强度的低估。这一现象是由于与VLSMs相关的能量重叠，掩盖了逆幂律区域。LCS分析估计壁面附着涡的流向与壁面法向之比约为14.3，其达到的高度约为湍流外流尺度的30%。
Abstract Recent works on wall-bounded flows have corroborated the coexistence of wall-attached eddies, whose statistical features are predicted through Townsend's attached-eddy hypothesis (AEH), and very-large-scale motions (VLSMs). Furthermore, it has been shown that the presence of wall-attached eddies within the logarithmic layer is linked to the appearance of an inverse-power-law region in the streamwise velocity energy spectra, upon significant separation between outer and viscous scales. In this work, a near-neutral atmospheric surface layer is probed with wind light detection and ranging to investigate the contributions to the streamwise velocity energy associated with wall-attached eddies and VLSMs for a very-high-Reynolds-number boundary layer. Energy and linear coherence spectra (LCS) of the streamwise velocity are interrogated to identify the spectral boundaries associated with eddies of different typologies. Inspired by the AEH, an analytical model for the LCS associated with wall-attached eddies is formulated. The experimental results show that the identification of the wall-attached-eddy energy contribution through the analysis of the energy spectra leads to an underestimate of the associated spectral range, maximum height attained and turbulence intensity. This feature is due to the overlap of the energy associated with VLSMs obscuring the inverse-power-law region. The LCS analysis estimates wall-attached eddies with a streamwise/wall-normal ratio of about 14.3 attaining a height of about 30 % of the outer scale of turbulence.