This study experimentally investigates the generation mechanism of a higher-angle lobe which is an acoustic field feature of a supersonic jet impinging on an inclined flat plate. The overall sound pressure level distribution and spectra, the conditional averages of near field schlieren movies, and the time-averaged wall pressure distribution were obtained for three cases of Mach 1.8 ideally expanded impinging jets with plate angles of $45°$, $22.5°$, and $10°$ to the jet downstream axis. In the $45°$ and $22.5°$ cases, a higher-angle lobe appears. The dominant acoustic waves in the higher-angle lobe are radiated from the source region that contains shock waves and are suggested to be correlated with large-scale turbulent structures. These results suggest that the higher-angle lobe is dominated by acoustic waves generated by the interaction between the shock waves and large-scale turbulent structures. This inference is supported by the fact that the near-field acoustic wave patterns are qualitatively reproduced by the interference of monopoles located near the shock waves in the $45°$ and $22.5°$ cases and that neither the shock wave nor the higher-angle lobe is observed in the $10°$ case.

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板角对超音速撞击射流声波影响的实验研究

本研究通过实验研究了高角度波瓣的产生机制，该波瓣是超音速射流撞击倾斜平板的声场特征。总体声压级分布和频谱、近场纹影电影的条件平均值和时间平均壁压力分布是获得了三种情况下的 1.8 马赫理想扩展撞击射流的板角为$45°$, $22.5°$， 和 $10°$到射流下游轴。在里面$45°$ 和 $22.5°$在这种情况下，会出现更高角度的波瓣。高角瓣中的主要声波从包含激波的源区辐射出来，并被认为与大尺度湍流结构有关。这些结果表明，高角瓣主要由冲击波和大尺度湍流结构相互作用产生的声波控制。这一推论得到以下事实的支持：近场声波模式是由位于激波附近的单极子的干涉定性再现的。$45°$ 和 $22.5°$ 在这种情况下，既没有观察到冲击波，也没有观察到更高角度的波瓣 $10°$ 案件。