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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。
Based on the discrete vortex method and vortex theory, a time-domain meshless method for predicting the sound of two-dimensional flat-panel wake is established. The method uses the decoupling method to complete the sound field calculation. Firstly, the discrete wake-vortex method is used to calculate the flow field of the flat wake under the uniform flow. The key parameters such as the vorticity, position and velocity of the vortex in the flow field are obtained. Then, In theory, a point vortex model of mid-vortex free space is established. The time-domain boundary element method is introduced to simulate the scattering of the sound field from the flat surface. The key features of the dipole sound field distribution and directivity are obtained. In-depth analysis of the contribution of the sound field by the upper and lower surface vortices and the plate scatter shows that the vortex shedding and rolling up and down from the upper and lower corners of the slab are dipole sources. The scattering of the slab makes the sound field to a certain extent strengthened, And the sound field has the dipole directivity characteristic whose maximum value is perpendicular to the surface of the slab. The established meshless method is fast and can acquire the key features of the flow field and sound field distribution at the same time, which can improve the basic understanding of the generation mechanism of aerodynamic noise and provide an engineering application value for the theoretical research of wake noise Reliable calculation method.