桨尖下反对旋翼BVI噪声特性的抑制分析

基于计算流体力学(Computational fluid dynamics,CFD)方法,分析研究了新型下反桨尖对前飞状态旋翼桨/涡干扰(Blade-vortex interaction,BVI)噪声特性的影响。首先,通过求解Navier-Stokes方程获得准确的噪声声源信息,湍流模型采用一方程S-A模型。采用双时间法进行时间推进,为了提高流场的收敛速度,在伪时间方向上使用高效的隐式LU-SGS格式推进,并采用并行算法进行加速。然后,在获得的可靠声源信息基础上,采用基于FW-H方程的Farassat 1A公式求解噪声。对有试验结果的算例进行了对比计算分析,验证了本文噪声预测方法的有效性。在此基础上,针对具有典型BVI噪声特征的前飞斜下降状态,开展了不同下反角度桨尖新型旋翼噪声辐射特性的计算分析,通过噪声辐射球的对比结果表明,选择适当的下反桨尖,可以有效地降低前飞斜下降状态下旋翼BVI噪声,从而达到较好的旋翼噪声抑制效果。

Reduction Anal yses on BVI Noise Characteristics of Rotor with Anhedral Angle Blade-Tip

Based on the computational fluid dynamics (CFD) method, the influence of new blade-tips with different anhedral angles on rotor blade-vortex interaction(BVI) noise in forward flight is researched. In order to get the detailed flowfield information for the rotor noise computation, a new CFD method is established based on the Navier-Stokes equations with Spalart-Allmaras turbulence model. The dual-time stepping method is employed to simulate the unsteady flow phenomenon, while the implicit LU-SGS scheme is applied to the pseudo-time marching. To further improve t he computational efficiency, a suitable parallel strategy is introduced in the developed code. Calculations on acoustics of helicopter rotor are conducted based on the Farassat 1A formula from FW-H equations, and the capability of this method is demonstrated by the comparisons of the numerical results with available experimental data. Based upon the method, the aeroacoustic characteristics of the rotor with different anhedral angles in oblique descent flight are analyzed, which demonstrate that the new blade tip with appropriate anhedral angles can reduce the rotor noise effectively, especially the BVI noise in oblique descent flight.