后端设置扰流板对圆柱流场与气动噪声影响

Influence of Attached Splitter Plate on the Flow and Flow-induced Noise Generated from Circular Cylinder

采用延迟分离涡模型进行数值模拟,基于涡声理论和声类比方法,计算分析雷诺数Re=6×104下后端设置不同长度扰流板(不大于圆柱直径)的圆柱杆件周围流场与气动噪声特性,并与具有相同特征长度的普通圆柱杆件工况进行对比。圆柱杆件远场气动噪声计算值与声学风洞测试结果的频谱曲线吻合良好,验证数值模拟的准确性。结果表明,圆柱后端加设扰流板后,流动分离形成的涡脱落发展被限制在扰流板两侧,使得类圆柱杆件尾迹内分离剪切层长度增加,涡运动耗散增强,近壁面涡旋波动强度和尾迹内规则涡脱落强度减弱,降低几何体周围近场四极子气动噪声源强度,同时减小类圆柱杆件气动力脉动和阻力平均值,降低涡脱落诱发气动噪声的谐频峰值,有效降低远场偶极子噪声的声压级幅值,取得较好的气动噪声降噪效果。

The characteristics of flow and aerodynamic noise generated around a circular cylinder using an attached splitter plate with different lengths(no more than cylinder diameter)have been studied and compared with the circular cylinder case of the same characteristic dimensions at a Reynolds number of 6x10*based on the theory of vortex sound and acoustic analogy approach after the flow is simulated using the delayed detached-eddy model.The calculated spectra of far-field aerodynamic noise agree well with the anechoic wind-tunnel experiments for the circular cylinder case,verifying the accuracy of the numerical simulations.Results show that the developing of the vortex shedding induced from the flow separations is limited along two sides of the splitter plate after it is attached at the rear of the cylinder.The separated shear layer developed in the wake of cylindrical bars is elongated and the dissipation of vortex motion is strengthened.The vortex undulation close to the walls and regular vortex shedding in the wake are mitigated.Thus the strength of near-field quadrupole sound source is reduced.Meanwhile the aerodynamic force fluctuation and mean drag are decreased.Consequently the harmonic peak values of flow-induced noise generated from the vortex shedding are reduced effectively and the corresponding amplitude of sound pressure level of far-field dipole sound source is decreased.Thereby a good aerodynamic noise reduction effect is achieved for a circular cylinder with an attached splitter plate.