平板湍流边界层湍动能时空多尺度分布特征与典型结构  

The spatial-temporal multi-scale characteristics of turbulent kinetic energy and typical structures in turbulent boundary layer

作　　者：王芊翔 范子椰 岳巾会 白建侠 程肖岐 田海平 姜楠 Qian-Xiang Wang;Zi-Ye Fan;Jin-Hui Yue;Jian-Xia Bai;Xiao-Qi Cheng;Hai-Ping Tian;Nan Jiang(Department of Mechanics,School of Mechanical Engineering,Tianjin University,Tianjin,300354,China;Department of Mathematics,Tianjin Renai College,Tianjin,301636,China;Department of Mechanics,Taiyuan University of Technology,Taiyuan,030024,China)

机构地区：[1]Department of Mechanics,School of Mechanical Engineering,Tianjin University,Tianjin,300354,China [2]Department of Mathematics,Tianjin Renai College,Tianjin,301636,China [3]Department of Mechanics,Taiyuan University of Technology,Taiyuan,030024,China

出　　处：《Acta Mechanica Sinica》2024年第3期61-71,共11页力学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.12202310,12202309,1233201712202309,and 12332017);Chinesisch-Deutsche Zentrum für Wissenschaftsförderung (Grant No.GZ1575);China Postdoctoral Science Foundation (Grant No.2022M712357).

摘　　要：应用四相机阵列高时间分辨粒子图像测速系统,测量平板湍流边界层7.26δ_(0.99)×1.18δ_(0.99)大视场瞬态速度场的大样本时间序列,实验雷诺数Re_(τ)=1046.在所有法向层沿流向方向进行空间多尺度连续小波变换,根据分尺度小波系数得到湍动能随脉动空间尺度和法向位置的分布;同时对每个空间点脉动速度时间序列在时间上进行多尺度连续小波变换,根据分尺度小波系数得到湍动能随脉动时间尺度和法向位置的分布;计算出去除多尺度相干结构前后的平坦因子随脉动空间尺度和法向位置的分布.使用空间小波系数过零点法对流场的湍流结构进行检测,用条件采样和空间相位平均的方法获得各尺度不同法向位置湍流结构的空间典型拓扑,发现湍流小尺度结构涡量的空间拓扑呈现沿流向和法向正负交替的四极子结构,流线表现为鞍点和焦点组成的动力系统,肯定了湍流小尺度结构的普适性;计算去除相干结构前后的标度指数ζ(p),发现多尺度相干结构是引起奇异标度律的原因.Time series of large samples of instantaneous velocity fields with a 7.26δ_(0.99)×1.18δ_(0.99) size in a turbulent boundary layer have been obtained by experimental measurement using time-resolved particle image velocimetry(TRPIV)with a four-camera array.The resultant experimental Reynolds number(Re_(τ))is 1046.The continuous spatial wavelet transform has been employed to convert the streamwise velocity fluctuations into multi-scale components in the streamwise direction at all wall-normal positions.The distribution of turbulence kinetic energy across all spatial scales and all wall-normal positions are determined from the multi-scale wavelet coefficients.The continuous temporal wavelet transform has also been utilized to resolve the temporal series of longitudinal velocity fluctuations into multi-scale temporal components at all wall-normal positions.The use of the multi-scale wavelet coefficients delivered the turbulent kinetic energy distribution across all temporal scales and all wall-normal positions.Moreover,the distribution of multi-scale flatness factors with spatial scales and normal position,before and after removal of multi-scale coherent structures,has been calculated.The turbulent structures are detected by zero-crossing the wavelet coefficients.The conditional sampling scheme and spatial phase-locked method have been employed to establish typical multi-scale structures at different wall-normal positions.The universality of the small-scale structures has been confirmed where the associated vorticity is characterized by an alternating positive and negative quadrupole along the longitudinal direction and wall-normal direction,while the streamlines can be considered a dynamic system composed of a saddle point and focal points.The scaling exponentϚ(p),before and after the removal of the coherent structures,has been calculated,confirming that the multi-scale coherent structures are responsible for the anomalous scaling law.

关 键 词：Arrayed TRPIV Turbulent boundary layer Coherent structure Wavelet transform Scaling law 

分 类 号：O3[理学—力学]