Results of an experimental study with a large aspect ratio rectangular nozzle, divided into multiple compartments or septa, as pertinent to distributed propulsion, are presented. Noise measurements at high-subsonic conditions show that the nozzle with the septa is quieter than the corresponding baseline nozzle without the septa. At relatively lower Mach numbers a high-frequency tone is heard. This is shown to be due to Karmann vortex shedding from the trailing edges of the partitions that separate a septum from the adjacent ones. Flowfield measurements for a six septa case show that the cellular flow structure, issuing from the nozzle, goes through a curious coalescence with increasing downstream distance (x) from the nozzle. Adjacent cells pair to yield a three-cell structure by x/D＝2, where D is the equivalent diameter of the baseline nozzle. By about x/D =16, both the septa case and the baseline case evolve to yield axisymmetric flowfields.
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机译：提出了一个与长径比大的矩形喷嘴有关的实验研究的结果，该矩形喷嘴与分布式推进有关，分为多个隔室或隔片。在高亚音速条件下的噪声测量表明，带有隔垫的喷嘴比没有隔垫的相应基线喷嘴更安静。在相对较低的马赫数下，会听到高频音。这表明是由于Karmann涡流从隔板的后缘脱落而引起的，隔板的后缘使隔垫与相邻隔垫分开。在六个隔垫情况下的流场测量结果表明，从喷嘴发出的蜂窝状流动结构随着离喷嘴下游距离（x）的增加而经历了好奇的合并。相邻的单元对通过x / D ＝ 2产生三单元结构，其中D是基线喷嘴的等效直径。大约x / D = 16时，隔垫情况和基线情况都会演变为产生轴对称流场。
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