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Effect of front inclined hole on flow structure around a wall-mounted cube
Experimental Thermal and Fluid Science ( IF 3.2 ) Pub Date : 2021-01-01 , DOI: 10.1016/j.expthermflusci.2020.110239
Jiawei Li , Hiroka Rinoshika , Akira Rinoshika

Abstract To control the wake flow around a wall-mounted cube, passive control is performed by drilling a front inclined hole (FIH) from the front surface to the free end of the cube. To study the control features and mechanism, controlled and uncontrolled cubes are experimentally investigated. A circulation water tunnel is used to perform PIV measurements, where the Reynolds number is ReD = 11550 based on the cube side length of D = 70 mm, and the thickness of the boundary layer on the tunnel bottom is δ/D = 0.25. To study the effect of the hole position, three FIHs with inlet heights of 20, 35, or 50 mm are investigated. The time-averaged flow fields show that the velocity of the FIH jet increases with the FIH inlet height. Comparing with the flow structures around standard cube, it is found that the reverse zone and shear layer above free-end are obviously suppressed due to the FIH jet. In addition, the scale of the reverse zone and arch-type vortex in the near-wake is reduced by the FIH jets. Because the FIH jets disrupt the development of wake vortices, the Reynolds shear stress and turbulent kinetic energy in the near-wake decrease. The control effect is most apparent for the cube with an FIH at a spanwise height of 50 mm (the FIH50 cube). In this case the effect of the free-end downwash flow on the wake is weaker, and the shedding frequency of the wake vortices near the free-end increases. Proper orthogonal decomposition analysis indicates that the FIH50 suppresses the alternately arranged flow features and enhances the symmetrically arranged features.

中文翻译:

前斜孔对壁挂式立方体周围流动结构的影响

摘要 为了控制壁挂式立方体周围的尾流,被动控制是通过从立方体的前表面到自由端钻一个前斜孔(F​​IH)来实现的。为了研究控制特征和机制,对受控和非受控立方体进行了实验研究。使用循环水隧道进行PIV测量,其中雷诺数为ReD=11550,基于立方边长D=70mm,隧道底部边界层厚度为δ/D=0.25。为了研究孔位置的影响,研究了入口高度为 20、35 或 50 毫米的三个 FIH。时间平均流场表明,FIH 射流的速度随着 FIH 入口高度的增加而增加。与标准立方体周围的流动结构相比,发现自由端上方的反向区和剪切层明显受到FIH射流的抑制。此外,FIH 射流减小了近尾流中的反向区和拱形涡旋的规模。由于 FIH 射流扰乱尾流涡的发展,近尾流中的雷诺剪应力和湍流动能降低。对于 FIH 在 50 mm 展向高度的立方体(FIH50 立方体),控制效果最为明显。在这种情况下,自由端下洗流对尾流的影响较弱,自由端附近尾流涡的脱落频率增加。适当的正交分解分析表明FIH50抑制了交替排列的流动特征并增强了对称排列的特征。FIH 射流减小了近尾流中的反向区和拱形涡旋的规模。由于 FIH 射流扰乱尾流涡的发展,近尾流中的雷诺剪应力和湍流动能降低。对于 FIH 在 50 mm 展向高度的立方体(FIH50 立方体),控制效果最为明显。在这种情况下,自由端下洗流对尾流的影响较弱,自由端附近尾流涡的脱落频率增加。适当的正交分解分析表明FIH50抑制了交替排列的流动特征并增强了对称排列的特征。FIH 射流减小了近尾流中的反向区和拱形涡旋的规模。由于 FIH 射流扰乱尾流涡的发展,近尾流中的雷诺剪应力和湍流动能降低。对于 FIH 在 50 mm 展向高度的立方体(FIH50 立方体),控制效果最为明显。在这种情况下,自由端下洗流对尾流的影响较弱,自由端附近尾流涡的脱落频率增加。适当的正交分解分析表明FIH50抑制了交替排列的流动特征并增强了对称排列的特征。近尾流中的雷诺剪应力和湍动能减小。对于 FIH 在 50 mm 展向高度的立方体(FIH50 立方体),控制效果最为明显。在这种情况下,自由端下洗流对尾流的影响较弱,自由端附近尾流涡的脱落频率增加。适当的正交分解分析表明FIH50抑制了交替排列的流动特征并增强了对称排列的特征。近尾流中的雷诺剪应力和湍动能减小。对于 FIH 在 50 mm 展向高度的立方体(FIH50 立方体),控制效果最为明显。在这种情况下,自由端下洗流对尾流的影响较弱,自由端附近尾流涡的脱落频率增加。适当的正交分解分析表明FIH50抑制了交替排列的流动特征并增强了对称排列的特征。
更新日期:2021-01-01
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