稀疏网格条件下的水下航行体低频水动力噪声计算
Low-frequency hydrodynamic noise calculation of underwater vehicle with sparse grid conditions
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摘要: 利用结构有限元结合声学有限元方法以及无反射边界条件, 构建了复杂结构受湍流边界层脉动压力激励的声振响应计算模型, 通过引入网格虚拟细化实现非相关流激载荷的修正, 解决了有限元模型网格尺寸与湍流边界层脉动压力空间相关性尺度的不兼容问题, 在满足声振响应要求的稀疏网格条件下实现了航行体低频水动力噪声计算。以典型回转体模型为例, 计算了其低频水动力辐射噪声, 与循环水槽试验结果和离散子单元法计算结果进行了比较, 三者趋势基本吻合, 重合频段偏差小于3 dB。该方法兼顾了计算精度和计算效率, 具有良好的适用性。Abstract: A computational model of the acoustic vibration response of complex structures excited by pressure fluctuations in the turbulent boundary layer is constructed by combining the structural finite element method, the acoustic finite element method, and non-reflecting boundary conditions. The issue associated with the mesh size of the finite element model and the spatial correlation scale of the pressure fluctuations in the turbulent boundary layer is solved by introducing the virtual grid refinement to accomplish the correction of the uncorrelated flow excitation loads. The underwater vehicle’s low-frequency hydrodynamic noise calculation is carried out under sparse grid settings that meet the demands of the acoustic vibration response. The typical underwater rotary vehicle model is used as an example to calculate its low-frequency hydrodynamic radiation noise. When compared to the results of the discrete subunit method calculation and the large cavitation channel test, the three results are generally consistent, with the deviation of the results in the overlapping frequency range being less than 3 dB. The method is highly applicable and takes into account calculating efficiency and accuracy.