A parametric study of the passive-suction-jet control scheme was experimentally performed for the cylinder model. The dependence of the control effectiveness on the gap thickness was determined for a cylinder model controlled by passive-suction-jet pipes at Reynolds number () values ranging from 20,000 to 60,000. The fluid forces and flow structure were measured on a cylinder model without any control and used to evaluate the control effectiveness. Proper orthogonal decomposition (POD) analysis, phase average, and triple decomposition were applied to the flow fields to explore the control mechanism. The results show that the pipe control was most effective when the gap thickness was 0.075. Too large or too small a gap thickness was not beneficial for controlling the resistance level, and the fluctuating lift was reduced to a tiny level as the thickness increased to 0.075. The steady jets ejected from the leeward slots rolled up into several small-scale standing vortices. These vortices modified the streamline topology of the model, developing a new saddle point in the wake. Moreover, the roll-up of the separated shear layers was restrained by the pipe, which inhibited the vortex formation and shedding processes and the unsteady forces exerted on the model.

中文翻译：

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被动吸射流控制下间隙厚度对圆柱体气动力和流动结构的影响

对气缸模型进行了被动吸射控制方案的参数化研究。控制效果对间隙厚度的依赖性是由被动吸入喷射管控制的气缸模型确定的，雷诺数 () 值范围为 20,000 至 60,000。在没有任何控制的气缸模型上测量流体力和流动结构，并用于评估控制有效性。将本征正交分解（POD）分析、相位平均和三重分解应用于流场以探索控制机制。结果表明，当间隙厚度为0.075时，管道控制最为有效。间隙厚度过大或过小都不利于控制阻力水平，当厚度增加到0.075时，波动升力减小到很小的水平。从背风槽喷出的稳定射流卷起成几个小规模的驻涡。这些涡流修改了模型的流线拓扑，在尾流中形成了新的鞍点。此外，分离的剪切层的卷起受到管道的限制，从而抑制了涡流的形成和脱落过程以及施加在模型上的不稳定力。