方腔流致振荡及噪声的数值研究

采用直接数值模拟方法,研究了低Reynolds数下L/D=2的方腔亚声速流致振荡现象及其诱导的噪声。结果表明,在所计算的参数范围内,振荡都是由Rossiter II模态主导;来流边界层变薄会导致低频成分的出现,其产生的直接原因是涡与后拐角撞击方式的切换,根源在于回流区与剪切层相互作用形式的不稳定。采用本征正交分解(POD)方法,分析了不同振荡形式所对应的本征模态涡结构及其与后拐角撞击方式的关系。计算得到并分析了声波的产生和传播过程,结果与已有实验结果和理论模型符合良好。

Numerical investigation of flow-induced oscillations and noise from a rectangular cavity

Direct numerical simulation is used to investigate flow-induced oscillations and noise for a low-Reynolds-number subsonic flow over a rectangular cavity with a constant configuration L/D=2.The results indicate that oscillations are dominated by Rossiter II mode in the range of present computational parameters.A low frequency component appears as the decreasing of the thickness of inflow boundary layer,which is directly caused by pattern switching of vortex-edge impingement.The inherent reason is unstable interaction between the recirculation zone and the shear layer.The proper-orthogonal-decomposition(POD) method is employed to analyze the influence of different oscillation pattern on the corresponding vortex structures of the intrinsic mode and its relation with vortex-edge interaction.Moreover,the process of noise generation and propagation is computed and analyzed,and the results are agreed well with available experiments and analytical model.