串列海豹胡须柱杆件周围流场与气动噪声特性分析

Characteristics of flow and flow‑induced noise generated from the tandem seal‑vibrissa‑shaped cylinder

  • 摘要: 根据延迟分离涡模型进行流场计算,采用稀疏促进动力学模态和谱本征正交分解方法对尾迹流场进行模态分解,结合声类比方法,分析了雷诺数(Re=6×104~1.2×105)下串列海豹胡须柱杆件周围流场与气动噪声特性,并与具有相同特征长度(对应圆柱直径30 mm)的串列圆柱与串列椭圆柱杆件工况进行对比。结果表明:串列类圆柱体下游杆件的升力脉动强于上游杆件,在噪声辐射中占据主要地位;海豹胡须柱鞍面与节点面交错排列的几何结构引发流体三维分离,削弱了流动中剪切层之间的相互作用,尾迹稳定性增强;串列海豹胡须柱破坏了串列圆柱交替涡脱落产生的卡门涡街,流动结构中存在相邻两鞍面产生的反向涡脱落,使部分横向力得到平衡,显著降低升力脉动和涡激振动,有效控制几何体表面非定常脉动力产生的气动噪声;串列海豹胡须柱在多数频段内气动噪声声压级幅值降低,具有较明显的降噪效果。声学风洞测试结果验证了气动噪声数值模拟的准确性。本文工作对类圆柱杆件气动噪声控制具有一定的参考价值。

     

    Abstract: Based on the flow simulations through delayed detached-eddy simulation model, the methods of sparsity-promoting dynamic mode decomposition and spectral proper orthogonal decomposition are applied for analysing the mode decomposition on the wake flow. Then combined by the acoustic analogy approach, this study investigates the behaviour of flow and aerodynamic noise generated around tandem seal-vibrissa-shaped cylinder in comparison with the cases of tandem cylinderlike and elliptical bars with the same characteristic length corresponding to the cylinder diameter of 30 mm for a range of Reynolds numbers (Re=6×104~1.2×105). Results show that the lift fluctuations of the downstream bars are stronger than those of the upstream bars and the downstream bars dominate the aerodynamic noise radiation. The alternative arrangement of the saddle and nodal planes of seal-vibrissa-shaped cylinder introduces three-dimensional flow separations and suppresses the shear layer interactions, improving greatly the flow stability. The structure destroys the regular vortex shedding of Karman vortex street occurring in tandem cylinder wake. The presence of reverse vortex shedding generated by two adjacent saddle surfaces in the flow of tandem seal-vibrissa-shaped cylinder makes the lateral force balanced partially and reduces significantly the lift fluctuations as well as the vortex-induced vibration. The aerodynamic noise generated by the non-constant fluctuating force exerted on the wall surfaces of bars are suppressed effectively. The sound pressure level is reduced at most frequencies. Thereby the tandem seal-vibrissa-shaped cylinder is demonstrated to have a significant noise reduction effect. The experimental measurements verify the accuracy of the aerodynamic noise predictions. The current work would provide a certain scientific research and engineering application value for the aerodynamic noise control on cylinderlike bars.

     

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