Combining PIV, POD and vortex identification algorithms for the study of unsteady turbulent swirling flows
Combining PIV, POD and vortex identification algorithms for the study of unsteady turbulent swirling flows
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DOI：
10.1088/0957-0233/12/9/307
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发表时间：
2001-09-01
影响因子：
2.4
通讯作者：
Grosjean, N
中科院分区：
文献类型：
--
作者：
Graftieaux, L;Michard, M;Grosjean, N
粒子图像测速（PIV）测量是在一个高度湍流旋流。在这种流动中，我们观察到湍流脉动和非定常旋涡运动的共存。适当的正交分解（POD）是用来分离这两个贡献的总能量。POD与两个新的涡识别函数Gamma（1）和Gamma（2）相结合。这些函数根据速度场确定涡流中心和边界的位置。POD计算的测量速度场表明，两个空间模式负责的平均涡中心的位置附近观察到的波动。这两种模式也负责大规模的相干性的波动。由Gamma（2）标量场计算的POD表明，大尺度涡旋的位移和变形与这些模态相关。我们建议使用这样的方法来分离伪波动由于不稳定的性质，大规模的旋涡波动由于小尺度湍流。
Particle image velocimetry (PIV) measurements are made in a highly turbulent swirling flow. In this flow, we observe a coexistence of turbulent fluctuations and an unsteady swirling motion. The proper orthogonal decomposition (POD) is used to separate these two contributions to the total energy. POD is combined with two new vortex identification functions, Gamma (1) and Gamma (2). These functions identify the locations of the centre and boundary of the vortex on the basis of the velocity field. The POD computed for the measured velocity fields shows that two spatial modes are responsible for most of the fluctuations observed in the vicinity of the location of the mean vortex centre. These two modes are also responsible for the large-scale coherence of the fluctuations. The POD computed from the Gamma (2) scalar field shows that the displacement and deformation of the large-scale vortex are correlated to these modes. We suggest the use of such a method to separate pseudo-fluctuations due to the unsteady nature of the large-scale vortices from fluctuations due to small-scale turbulence.