A noise source characteristic of an unheated compressible jet is experimentally investigated for the jet with exit Mach number 0.8. Measurements of acoustic pressure fluctuations were performed in the near-field and far-field independently to identify noise source characteristics using the correlation technique. Near-field and far-field acoustic pressure fluctuations were also measured simultaneously to identify the acoustic component in near-field pressure fluctuations measured. Measurements were taken for the base and chevron nozzle with the nozzle exit diameter of 30 mm. From auto-correlation and cross-correlation in the near and far fields, it is observed that region surrounding to mixing layer is dominated by random small scale structures which radiate noise to sideline direction in the far-field. Correlation obtained at downstream of the potential core in the near-field represents the dominance of coherent large scale structure which radiates the noise to the far-field in the aft angle direction. Chevron changes the characteristics of noise sources. The size of the dominant large-scale noise source reduces due to chevron. Coherence of the noise source in the region surrounding to mixing layer reduces due to chevron which is responsible for reducing the energy of the dominant noise sources downstream of the potential core. Near-field far-field cross-correlation confirms that spatial near-field location for radiating acoustic pressure fluctuations more efficiently to the far-field at polar angle 30° is dependent on axial as well as transverse position in the near-field. Chevron reduces the convective velocity of the flow. Chevron also reduces the spatial correlation length scale of the dominant noise source. Chevron changes the acoustic pressure in the near-field thereby shifting the dominant noise source towards the nozzle exit.

针对出口马赫数为 0.8 的射流，对未加热的可压缩射流的噪声源特性进行了实验研究。在近场和远场独立进行声压波动的测量，以使用相关技术识别噪声源特征。还同时测量了近场和远场声压波动，以识别测量的近场压力波动中的声学分量。对喷嘴出口直径为 30 毫米的底座和 V 形喷嘴进行了测量。从近场和远场的自相关和互相关可以看出，混合层周围的区域以随机小尺度结构为主，这些结构在远场向边线方向辐射噪声。在近场潜在核心下游获得的相关性代表了相干大尺度结构的主导地位，该结构将噪声辐射到后角方向的远场。雪佛龙改变了噪声源的特性。由于 V 形花纹，主要的大规模噪声源的尺寸减小。混合层周围区域中噪声源的相干性由于 V 形花纹而降低，V 形花纹负责降低潜在核心下游的主要噪声源的能量。近场远场互相关证实，用于以 30° 极角更有效地向远场辐射声压波动的空间近场位置取决于近场中的轴向和横向位置。Chevron 降低了流动的对流速度。Chevron 还降低了主要噪声源的空间相关长度尺度。Chevron 改变近场中的声压，从而将主要噪声源移向喷嘴出口。