气动噪声预测中非紧致格林函数的数值计算方法

Numerical Method for Aerodynamic Noise Prediction Using Exact Green’s Function

采用声模拟理论预测非紧致结构与非定常流动相互作用诱发的气动噪声时,为考虑边界对声场的散射影响,需要应用非紧致格林函数。为此,发展了一种基于边界元思想的非紧致格林函数数值计算方法,该方法适用于任意外形结构,能直接计算非紧致格林函数及其偏导数。以二维圆柱边界为算例,采用理论解析方法推导了非紧致格林函数及其偏导数的正确表达式,并将数值计算方法结果与理论解析方法结果相比较,验证了数值方法的正确性。

The exact Green＇ s function needs to be employed when predicting the aerodynamic noise induced by the interaction between non-compact structure and unsteady flow using acoustic analogy theory. However, except for the very simple geometries, the exact Green＇s function has to be found numerically. Thus, a numerical method in virtue of Boundary Element Method was presented, with which the exact Green＇ s function and its spatial derivatives in frequency domain could be computed directly. Taking a two-dimensional cylinder as an example, the analytical expressions of the exact Green＇ s function and its spatial derivatives were deduced. And all the corresponding numerical results were in good agreement with the analytical ones, indicating that the proposed method was available for noise prediction.