槽道内涡波流场的POD分析

对槽道内涡波流场的瞬态速度矢量场进行了2DPIV测量实验，将2DPIV测量的矢量场数据进行POD分析，根据POD分解的各阶模态的能量比确定了表征涡波流场主导结构的前15阶模态。结果表明，POD分解的前15阶模态发现槽道内涡波流场是由槽道壁面剪切层诱导的涡列以及伴随的波状主流组成；流场中大尺度的涡旋发展为涡对，对波状主流的脉动频率产生影响；根据涡波流场中的驻点和鞍点，获取了流场的大尺度涡对、平均流场以及Helmholtz涡环等明显特征；最后根据POD分解的前15阶模态对槽道内涡波流场进行重组，重组流场表征了槽道内层流状态下波状主流的形态和涡旋共存的涡波结构以及驻点和鞍点的位置处涡旋的变化等主要特征，有效地剔除了PIV测量流场中的随机信息，保留了PIV测量流场的主导特征。

Proper orthogonal decomposition study on vortex wave field behavior of channel flow

Transient velocity vector field of the channel vortex wave field was experimentally measured out using two-Dimension Particle Image Velocimetry (2DPIV).Proper Orthogonal Decomposition (POD) technique was used to analyze the vector field data measured by 2DPIV,and the first 15 modes were determined by the mode energy rate,which represented characteristics of dominated structure of the vortex wave field.The results showed that the first 15 modes of POD decomposition reflected the characteristics of the channel vortex wave field comprised of vortex columns induced by channel wall shear layers and accompanied wavy mainstream.The mainstream wavy pulsation frequency was affected by the vortex pair through the development of large-scale vortexes;According to vortex wave field in the stagnation point and the saddle point, distinctive features were obtained,i. e.,a large-scale vortex pair of the field,an average flow field and Helmholtz vortex ring.The vortex wave field was reconstructed in accordance with the first 15 modal vortexes.The reconstructed field represented the main features of a vortex wave structure of wavy mainstream forms,vortex of coexistence conditions,and the characteristics of the vortex flow changes in the stagnation points,saddle point position of field of channel laminar flow,remove.The random information of PIV measurements flow field was removed effectively,and the dominant features PIV measurements flow fields were retained.