【摘要】 低频窄带噪声是缝翼噪声的重要组成部分,研究其产生机制是缝翼噪声抑制的重要途径。基于30P-30N多段翼的瞬态流场分析,采用本征正交分解(POD)和动态模态分解(DMD)方法研究缝翼瞬态压力脉动的模态结构特征,获得缝翼瞬态流场主要特征模态以及窄带频率分布;利用经验模态分解(EMD)和互相关分析,保留原始瞬态压力信号的低频特性进行重构,并根据特征点的延迟时间及几何关系确定低频窄带噪声源位置。研究结果表明,低频窄带声源主要集中在特征模态压力脉动较大区域,如缝翼尾缘、剪切层下游及回流区;同时,在非特征模态的缝道及主翼前部区域也存在低频窄带声源,这些区域主要特征为由剪切层撞击壁面引起的缝翼尾缘与主翼前缘之间流场结构的相互作用。更多还原

【Abstract】 Low-frequency narrow-band noise is one of the important components in the slat noise. Based on the transient flow field analysis for multi-element airfoil 30 P-30 N, the main mode characteristics of the slat pressure fluctuation are analyzed by means of proper orthogonal decomposition(POD) and dynamic model decomposition(DMD), and the key feature modes and the distribution of narrow-band frequencies for the slat are obtained. Empirical mode decomposition(EMD) and cross-correlation analysis are used to reconstruct the signal by preserving the low frequency characteristics of the original transient pressure signal. The locations of noise sources of the low-frequency narrow-band are determined according to the delay time and geometric relationship for characteristic points. The results show that the low-frequency narrow-band sound sources are mainly concentrated on regions of feature modes with large pressure fluctuations, such as slat trailing edge, downstream of the shear layer and the recirculation zone. Meanwhile, there are still some sound sources of low-frequency narrow-band distributed in regions of non-featured modes. The key characteristics of these regions are the interaction of flow structure between the trailing edge of the slat and the leading edge of the main wing due to collision of the shear layer.更多还原