A New Time Domain Formulation for Broadband Noise Predictions
A New Time Domain Formulation for Broadband Noise Predictions
复制标题
宽带噪声预测的新时域公式
DOI：
10.1260/147547202320962574
复制
发表时间：
2002
影响因子：
1
通讯作者：
F. Farassat
中科院分区：
文献类型：
--
作者：
J. Casper;F. Farassat
本文用Farassat提出的一个新的声学分析结果“公式1B”，在时域内计算薄翼型非定常表面压力分布的加载噪声。该公式是带加载源项的Ffowcs Williams-Hawkings方程的一种新的解。该公式包含一个远场表面积分，它取决于时间导数和翼型上的压力的表面梯度，以及翼型表面的边界上的轮廓积分。作为第一个测试案例，新的配方是用来计算从平板辐射的噪声，通过一个恒定频率的正弦阵风移动。该试验工况的非定常表面压力是从基于线性翼型理论的结果中解析得出的。该测试用例用于检查公式1B的速度缩放特性，并证明其与Farassat公式1A的等效性。新的声学公式，再次与分析表面压力，然后被用来预测宽带噪声辐射的翼型沉浸在均匀的，各向同性的湍流。结果与Paterson和Amiet先前报道的实验数据进行了比较。预测和测量之间的良好协议。最后，描述了公式1B的另一种形式，用于宽带噪声的统计分析。
A new analytic result in acoustics called “Formulation 1B,” proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specied from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.