基于结构化多孔表面定常吸气的圆柱绕流场控制

CONTROL OF FLOW PASSING A CIRCULAR CYLINDER BY STEADY SUCTION BASED ON A STRUCTURED POROUS SURFACE

  • 摘要: 通过风洞试验研究了在雷诺数为10 000时圆柱尾流主动流动控制效果,流动控制通过基于结构化多孔表面定常吸气实现,试验工况具有不同的等效吸气系数Cμ。尾流的二维流场测量通过粒子图像测速(PIV)实现,在瞬时流场结果的基础上进行本征正交分解(POD)得到模态特性、瞬时涡量演变、脉动速度功率谱、时间平均流动特性和阻力系数估计等的分析与对比,评估流动控制效果。试验结果表明:施加流动控制后的流场POD模态能量分布发生变化,旋涡的顺流向能量输运过程得到增强,当Cμ足够大时,旋涡脱落模式发生改变。剪切层沿顺流向延长,上下剪切层之间趋于平行,涡量值得到削弱。脉动速度的主频被削弱,湍流的波动和动量交换效应得到抑制;阻力系数估计值可降至无控圆柱的约11%。

     

    Abstract: Active flow control effects of the circular cylinder wake flow with a Reynolds number of 10000 are investigated by wind tunnel tests. The flow control is conducted by steady suction based on a structured porous surface, and the test cases have various equivalent suction coefficient Cμ. The two-dimensional wake flow fields are measured by particle image velocimetry (PIV) technique. Based on the flow fields, the results of proper orthogonal decomposition (POD) modal characteristics, instantaneous vorticity evolution, power spectrum density of fluctuating velocity, time-averaged flow characteristics and drag coefficient estimation are analyzed and compared to evaluate the flow control effects. The results show that under flow control, POD modal energy distributions are changed, the streamwise vortex energy transportation process is strengthened and the vortex shedding mode is transformed when Cμ is large enough. The shear layers are elongated along the streamwise direction, and the upper and lower layers become parallel to each other; while the vorticity values are restrained. The dominant frequency of the fluctuating flow velocity is curbed and the turbulence fluctuation and momentum exchange effects are suppressed. The estimated drag coefficient can be reduced up to about 11% of that of the uncontrolled cylinder.

     

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