一种预测平板尾迹噪声的时域无网格方法

基于离散涡方法和涡声理论建立了一种预测二维平板尾迹发声的时域无网格方法。该方法应用解耦方式完成声场计算,首先使用离散涡方法计算了均匀来流作用下的平板尾迹流场,得到了流场中点涡的涡量、位置和速度等关键参数,然后基于涡声理论建立了自由空间中点涡发声模型,并引入了时域边界元方法来模拟平板表面对声场的散射作用,计算得到了平板尾迹涡发声的偶极子声场分布和指向性等关键特征。通过对上下表面涡以及平板散射对声场贡献的深入分析表明,从平板尾缘上下角点脱落并卷起的涡团均为偶极子源,平板的散射作用使得声场在一定程度上得到加强,并且使声场具有极大值方向垂直于平板表面的偶极子指向性特征。所建立的无网格方法计算快速,能同时获得流场和声场分布的关键特征,可提升对气动噪声产生机理的基本认识,同时还为尾迹噪声的理论研究提供了一种具有工程应用价值的可靠计算方法。

A grid-less time domain method for plate trailing edge noise prediction

A grid-less time domain method for predicting trailing edge noise radiated from a two-dimensional flat plate is established in the present study, which is based on the discrete vortex method and vortex sound theory. The trailing edge noise is calculated in a decoupling manner. Firstly, the shear layer shed from the plate trailing edge is simulated through a discrete vortex method, and the key parameters of the vortices are obtained, including the strengths, positions and velocities. Then, a sound radiation model of the vortices in the free space is deduced in the frame of the vortex sound theory. Besides, to account for the influence of the plate surface, a time domain boundary element method is introduced. After that, the sound pressure distribution and the far field directivity radiated from the trailing edge vortices are analyzed. The present results indicate that the vortex clouds rolled up by point vortices are typically dipole sources, and the scattering effect from the plate surface can not only enhance the sound pressure level but also lead the maximum sound pressure to propagate in the vertical direction to the surface. This grid-less model depicted here simulates the flow and sound field simultaneously, which can help to improve the basic understanding on the trailing edge noise radiation and provide a reliable method for noise investigation with engineering importance as well.