孔腔脉动压力及其波数—频率谱的大涡模拟研究

孔腔流动中包含着流动分离和失稳以及涡旋相互干扰等复杂的流动现象。孔腔涡旋流动引起的流体振荡能够引起脉动压力的显著增加从而产生强烈的噪声,在工程实际中备受关注。湍流脉动压力是流激噪声的重要来源,也是湍流研究中的基础性问题,对其进行数值计算研究是流声耦合领域的重要内容,而湍流脉动压力波数—频率谱的构建更是该领域的技术难点。文章采用大涡模拟方法(LES)对孔腔脉动压力进行了数值模拟,考察了四套网格和四种亚格子应力模型对计算结果的影响,并与试验结果进行比较,验证数值计算方法的可靠性。首先采用大涡模拟方法计算了孔腔的脉动压力,并与中国船舶科学研究中心的空泡水筒试验结果进行对比分析。接着详细地分析孔腔脉动压力,研究亚格子应力模型和网格数量对计算结果的影响。最后,对数值计算得到的脉动压力多元阵列结果进行时间/空间Fourier变换,构建了三维脉动压力波数-频率谱。该文工作对今后流激结构振动噪声的预报和流动控制研究奠定了基础。

Computation of wall pressure fluctuations and wavenumber-frequency spectrum of cavity using large eddy simulation

Cavity flow always contains phenomenon of flow separation, flow instability and vorties interac-tion, which can cause fluid oscillations. The fluid oscillations increase pressure fluctuations intensely and induce obvious noises. It is a serious concern in naval application. Wall pressure fluctuations beneath tur-bulent boundary layers are important sources of flow induced noise. The research of wall pressure fluctuation is one of the groundworks in turbulent research. Thus, numerical simulation of pressure fluctuations has be-come an important issue in the flow-acoustic coupling field and construction of wavenumber-frequency spectra of turbulent pressure fluctuations is the technological difficulty in turbulence research. In this pa-per, wall pressure fluctuations of cavity are calculated by using large eddy simulation (LES) and the effects of different grid numbers and four different sub-grid scale models on calculated results are discussed. The computed results are compared with experimental data to verify the reliability of the numerical method. First, wall pressure fluctuations of cavity are computed by LES. The computed results are compared with the experimental data in cavitation tunnel of CSSRC. Then, wall pressure fluctuations are analyzed particular-ly. The effects of different grid numbers and different sub-grid scale models are also discussed in detail. Finally, wavenumber-frequency spectra of wall pressure fluctuations of sensors array are calculated by time-space Fourier Transformation. It lays a foundation for further research in the prediction of flow induced vibration noise and flow control approach.