开缝圆柱缝隙倾斜角对脱落涡的影响

Effect of angle of slit on shedding vortex of slotted circular cylinder

开缝圆柱绕流作为钝体绕流研究的分支,具备很强的应用前景,但是对其复杂的流动现象的物理本质的理解仍不完善。本文采用流动显示技术和粒子成像测速技术(PIV),探究缝隙对开缝圆柱流场结构的影响,在数据处理方面采用本征正交分解(POD)方法对开缝圆柱流场信息进行了重建。实验研究表明:在一定雷诺数范围内,开缝圆柱缝隙的存在从根本上改变了圆柱绕流近区尾流的结构;开缝圆柱脱落涡的脱落频率对开缝圆柱缝隙倾斜角具有一定的敏感性,随着缝隙倾斜角的增大其斯特劳哈尔数逐渐变大,对比发现开缝圆柱狭缝比(缝隙/直径)为0.15时较0.10的斯特劳哈尔数具有更强的稳定性。

Vortex shedding from a circular cylinder with a slit which belongs to the unsteady flow of bluff bodies has very strong application prospects. However,it is still difficult to fully understand the complex flow phenomenon. Using flow visualization and particle image velocimetry（ PIV） measurement,we explored the influence of a slit on the flow field structure. Adopting the method of proper orthogonal decomposition（ POD）,we reconstructed the flow field in the series of operations on PIV data. The experimental results show that the flow in the slit demonstrates periodic motion,and this oscillating vent-flow greatly alters the near wake flow features within a certain range of Reynolds number. Shedding vortex frequency of slotted cylinder has certain sensitivity with the angle of slit. The Strouhal number increases gradually with the increase of the angle,and the Strouhal number of slit ratio（ slit / diameter） equals to 0. 15 is more stable than that of slit ratio equals to 0. 10.