An experimental time-resolved particle-image velocimetry study was conducted on wavy cylinders possessing wavelength (λ) and amplitude (a) combinations that are significantly different from earlier studies at Re_Dm = 2700. Results show that vortex formation length increases as the wavelength decreases from λ/D_m = 2.4 to 1.2, but decreases when the latter decreases to λ/D_m = 0.6. Amplitude increments lead to significant vortex formation length growths and reductions at the saddles/nodes of λ/D_m = 2.4 and 1.2 wavy cylinders, respectively. In contrast, λ/D_m = 0.6 wavy cylinders produce significantly shorter vortex formation lengths like a baseline cylinder, regardless of amplitude. Regular reversed flow “lobes” are observed for λ/D_m = 2.4 and 1.2 wavy cylinders, but not λ/D_m = 0.6 ones, which lead to variations in the spanwise vortex formation lengths. Proper orthogonal decomposition (POD) analysis shows that only a/D_m = 0.4, λ/D_m = 0.6 wavy cylinder has the same vortex-shedding frequency as the baseline cylinder. Other POD results also demonstrate that the vortex-shedding behaviour between λ/D_m = 0.6 wavy and baseline cylinder is very similar. The present study shows that there exists a minimal wavelength below which that coherent streamwise vortices will not be produced and wake control benefits of wavy cylinders will be considerably reduced.

对具有波长 (λ) 和振幅 (a) 组合的波浪圆柱体进行实验性时间分辨粒子图像测速研究，这些组合与 Re _Dm  = 2700 的早期研究有显着差异。结果表明，涡流形成长度随着波长的减小而增加从 λ/D _m  = 2.4 到 1.2，但当后者减小到 λ/D _m  = 0.6 时减小。振幅增量导致 λ/D _m  = 2.4 和 1.2 波浪圆柱体的鞍点/节点处的涡流形成长度显着增加和减少。相反，λ/D _m = 0.6 波浪圆柱体产生明显更短的涡流形成长度，如基线圆柱体，无论振幅如何。_{对于 λ/D m} = 2.4 和 1.2 波浪圆柱体，观察到规则的反向流动“波瓣”  ，但对于 λ/D _m  = 0.6 波浪圆柱体则观察不到，这会导致展向涡流形成长度发生变化。本征正交分解 (POD) 分析表明，只有 a/D _m  = 0.4，λ/D _m  = 0.6 的波浪圆柱体具有与基线圆柱体相同的涡旋脱落频率。_{其他 POD 结果也表明 λ/D m}之间的涡流脱落行为 = 0.6 波浪和基线圆柱体非常相似。目前的研究表明，存在一个最小波长，低于该波长将不会产生相干的流向涡流，并且波浪圆柱体的尾流控制优势将大大降低。