悬停状态下旋翼旋转噪声的分析

对直升机悬停时旋翼的旋转噪声进行了初步研究，分别用单极子和偶极子声源描述旋翼的厚度噪声和载荷噪声，并根据悬停状态下旋翼气动载荷的特点，用傅立叶级数表示旋翼桨盘上各点的气动力和法向气流速度，然后代入单极子和偶极子声源声辐射公式中，求出旋翼桨盘外某观察点的声压值。最后结合一算例，分析悬停状态下旋翼旋转噪声的辐射特性和不同的展向载荷分布模型对计算结果的响应。

Theoretical Analysis of Rotational Noise in Hovering Rotors

Rotorcraft noise has become a subject of considerable interest in the helicopter industry. This paper presents the initial work toward rotational noise prediction for hovering rotors. Rotor rotational noise is decomposed into thickness and loading noises modeled by monopole and dipole independently. Since the hovering rotor aerodynamic force has period characteristics, the Fourier series is used to describe the aerodynamic force on rotor disk and the air velocity out of the rotor disk. Then the sound pressure at some observation points is obtained in frequency dominant. The sound pressure level is calculated by an example rotor hovering in the sea level. The radiation characteristic of rotor rotation noise is discussed based on the calculational results.