Analyses on flow structures behind a wavy square cylinder based on continuous wavelet transform and dynamic mode decomposition
Analyses on flow structures behind a wavy square cylinder based on continuous wavelet transform and dynamic mode decomposition
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基于连续小波变换和动力模态分解的波浪方柱体流动结构分析
DOI：
10.1016/j.oceaneng.2020.108117
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发表时间：
2020-11
影响因子：
5
通讯作者：
Akira Rinoshika
中科院分区：
文献类型：
--
作者：
Dan Zhang;Hiroka Rinoshika;Yan Zheng;Akira Rinoshika
为了了解展向周期扰动下的尾流特性，对方形和波方后的流场结构进行了对比研究。在雷诺数为4075时进行了高速PIV测量。时均流场分析表明，波浪形前缘触发了沿着展向的交替二次涡。瞬态流场分析表明，波形前缘将常规的非对称涡脱落模式转变为对称涡脱落模式。结果表明，基于连续小波变换的波形前缘抑制了周期性的大尺度流动，而增强了小尺度涡结构的运动。动态模态分解的模态能量分布表明，波浪形前缘削弱了大尺度涡结构的优势，促进了大尺度涡结构向小尺度涡结构的转变。动模DM1和DM2在流向平面上的空间分布表明，波形前缘通过扭曲卡门涡及其相应的二次涡结构改变了尾流，使涡结构更不稳定，消散更快。基于时间系数的相位平均过程显示，在脱落过程中，波形方柱的分离剪切层向下游扩展，分离涡破碎成多个相对较小的涡.
A comparative study on the flow structures behind square- and wavy-square were performed to understand the wake characteristics under spanwise periodic perturbation. The high-speed PIV measurements were carried out at Reynolds number of 4075. The time-averaged flow field suggested that wavy leading edge triggered the alternative secondary vortices along the span. The instantaneous flow field indicated that the regular asymmetric vortex shedding mode was changed to symmetric mode by wavy leading edge. It was found that periodical large-scale flows were suppressed, while the motions of small-scale vortical structures were enhanced by the wavy leading edge based on the continuous wavelet transform. The modal energy distribution of the dynamic mode decomposition suggested that the wavy leading edge weakened the dominance of large-scale vortical structure and promoted the transition from large-scale to small-scale vortical structure. The spatial patterns of representative dynamic modes DM1and DM2in streamwise plane indicated that the wavy leading edge changed the wake flow by the distortion of Karman vortex and its corresponding secondary vortical structure, which made the vortical structures more unstable and dissipates more quickly. Furthermore, the phase averaging process based on temporal coefficients of DM1and DM2revealed that the separated shear layer of wavy square cylinder extended to further downstream and the separated vortex was broken into several relatively small vortices during the shedding process.
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影响因子：
3.7
作者：
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通讯作者：
Rupad Darekar;S. Sherwin
DOI：
10.1016/j.jweia.2015.06.011
发表时间：
2015-10
影响因子：
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作者：
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