用快速多极方法预测圆柱绕流的气动噪声

采用声模拟理论预测气动噪声时需要大量的计算时间，快速多极方法将传统点对点计算转变为点集之间的相互作用，可以有效加速计算。基于二维自由空间格林函数的分波展开方式，推导了FW-H方程应用快速多极变换后的积分核函数与计算公式。计算了低马赫数圆柱绕流的非定常流场；并由此预测了气动声源。随后，分别采用传统方法和快速多极方法计算其声场分布。结果表明，基于分波展开方式的快速多极方法能准确计算圆柱绕流气动噪声，在频率较低时能大幅减少声场计算时间，且观测点数越多，加速效果越明显。

Fast Multipole Method Applied in Prediction of Aeroacoustics Induced by a Circular Cylinder

Prediction of aeroacoustics using acoustic analogy is a time- consuming process,while the fast multipole method which changes traditional way of node- to- node computing into set- to- set interaction can accelerate the process effectively.In this paper,the FW-H equation and its integral kernel function are derived with the fast multipole method based on the partial-wave expansion formulation of free-space Green＇s function.The unsteady flow field with low Mach＇s number near a two-dimensional circular cylinder is computed and exported as the sound source,and the sound field is obtained via traditional method and the fast multipole method.The results show that the fast multipole method based on partial-wave expansion can calculate the aerodynamic noise accurately,and reduce the computing time greatly for relatively low frequencies.And the acceleration effect is more obvious with larger number of observers.