The flow around a circular cylinder under bleed control is experimentally investigated in a water tunnel. The bleed jets are issued from the narrow slots directed from the front stagnation point to the positions near the upper and lower separation points. The Reynolds numbers based on the cylinder diameter are Re = 400, 780, and 1470, while the widths of the bleed slot are selected as w/D = 0.05, 0.1, and 0.2. The bleed jet interacts with the boundary layer, postponing the separation point to be near the downstream edge of the slot. It further modifies the wake shear layer, which moves away from the centerline. Thus, the recirculation bubble downstream of the circular cylinder is enlarged and the near wake width are increased, resulting in an increased vortex formation length and a decreased vortex shedding frequency. Such changes of the flow field increase with the bleed width. The vortex dynamics is also analyzed, showing that the wake pattern could be modified by the bleed control. The wake vortex is converted into a bistable mode at w/D = 0.1 and 0.2, Re = 780 and 1470, where the symmetric and asymmetric modes are both observed, while all the control cases at Re = 400 still show the asymmetric mode.
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机译：在泄水控制下，在水隧道中对圆柱体周围的流动进行了实验研究。从前停滞点指向窄狭缝的排气口流到上下分离点附近的位置。基于圆柱直径的雷诺数分别为Re = 400、780和1470，而泄放槽的宽度选择为w / D = 0.05、0.1和0.2。引流与边界层相互作用，将分离点推迟到槽的下游边缘附近。它进一步修改了远离中心线的尾流剪切层。因此，圆筒下游的再循环气泡增大并且近尾流宽度增大，导致增加的涡流形成长度和减小的涡流脱落频率。流场的这种变化随着排放宽度的增加而增加。涡流动力学也进行了分析，表明尾流模式可以通过排放控制进行修改。在w / D = 0.1和0.2，Re = 780和1470时，尾流涡流被转换为双稳态模式，其中均观察到对称和非对称模式，而在Re = 400时，所有控制情况仍显示为非对称模式。
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