Abstract Flow patterns downstream of the hollow square cylinder with slots are experimentally investigated to show effect of the slot ratio on the wake flow characteristics and turbulence statistics at Reynolds number of Re = 6000 using the particle image velocimetry (PIV) technique. Proper orthogonal decomposition (POD) analyses indicate that the self-issuing jet dramatically changes the mechanism of vortex shedding interaction. Penetration of the self-issuing jet into the wake region leads to increasing of the vortex formation length for low slot ratios. On the other hand, the self-issuing jet penetrates further downstream due to increasing momentum coefficient of the jet and splits the wake region in half for high slot ratios. Strouhal number increases with the increasing slot ratio and it attains approximately the twofold of the solid cylinder case, since the self-issuing jet accelerates the vortex shedding process. However, turbulence statistics are significantly reduced for all slot ratios. Distributions of the spectral density in the wake region of the cylinder indicate that the vortex shedding instability could be reduced considerably by the slotted cylinder. Drag coefficient, which is estimated from PIV data, reduces up to 42% in comparison with the solid cylinder model.

中文翻译：

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带槽的中空方柱体下游的流动拓扑

摘要 实验研究了带槽的中空方柱体下游的流动模式，以使用粒子图像测速 (PIV) 技术显示在雷诺数 Re = 6000 时槽比对尾流特性和湍流统计的影响。适当的正交分解 (POD) 分析表明，自发射流极大地改变了涡旋脱落相互作用的机制。自发射流进入尾流区域会导致低狭缝比的涡旋形成长度增加。另一方面，由于射流的动量系数增加，自发射流进一步向下游渗透，并将尾流区域分成两半以实现高槽比。斯特劳哈尔数随着槽比的增加而增加，它大约是实心圆柱体情况的两倍，因为自发射流加速了涡旋脱落过程。但是，所有槽比的湍流统计数据都显着减少。圆柱尾流区域的谱密度分布表明，开槽圆柱可以显着降低涡旋脱落不稳定性。根据 PIV 数据估计的阻力系数与实心圆柱模型相比降低了 42%。圆柱尾流区域的谱密度分布表明，开槽圆柱可以显着降低涡旋脱落不稳定性。根据 PIV 数据估计的阻力系数与实心圆柱模型相比降低了 42%。圆柱尾流区域的谱密度分布表明，开槽圆柱可以显着降低涡旋脱落不稳定性。根据 PIV 数据估计的阻力系数与实心圆柱模型相比降低了 42%。