圆柱绕流气动声的偶极子及四极子源法定量研究

以亚临界三维圆柱绕流的气动噪声为对象,研究声类比理论中偶极子及四极子源模型在预测低Mach数流动气动声的可靠性及准确性。使用大涡模拟(LES)得到非定常流场,并依据声类比中的Curle等效偶极子面源和Lighthill四极子体源模型,提取相应的声源数据,经Fourier变换得到涡脱落频率处的声源信息,进而定量预测圆柱绕流的气动声。结果表明:Curle模型的结果与实验结果吻合良好,Lighthill体源模型预测的准确性依赖于声源区域截断,不恰当的声源截断将导致错误的声场预测。 

Quantitative study of the aerodynamic sound induced by the flow past a cylinder based on dipole and quadrupole models

Computational fluid dynamics (CFD) associated with acoustic analogy theory was employed to numerically study the aerodynamic sound induced by the flow past a cylinder in the subcritical regime. The goal is to testify the reliability and accuracy of Curle's dipole and Lighthill's quadrupole source models according to the acoustic analogy theory. The 3-D unsteady turbulent flow fields were calculated by Large Eddy Simulation (LES) method. The equivalent sources were extracted from the time history flow data with Fourier Transform applied to extract the components at the vortex shedding frequency. The sound radiation by Curle's theory was obtained by a numerical surface integral, and a good agreement with the sound measurement was found. The sound radiation of Lighthill's quadrupoles was obtained by solving the inhomogeneous Helmholtz equation, and erroneous results might arrived at if the volumetric sources were truncated inappropriately. The study indicates that Curle's model is superior to Lighthill's model based on its more reliable results and low computational cost.