This paper investigates the structural response of rectangular nozzles during their supersonic operation. The nozzles in this study are known as Single Expansion Ramp Nozzles (SERNs), with Throat Aspect Ratios (TARs) ranging from 6 to 9 and a designed Mach number of 1.5. Under and approaching the strongest off-design flow conditions, in both underexpanded and overexpanded flow regimes, periodic modulation of screech amplitude is observed. The nearfield pressure signature of the modulation phenomenon and its frequency characteristics show that its origin is the excitation of a structural mode of the nozzle wall and not a fluid–acoustic phenomenon, like screech with Strouhal number characteristics. The modulation behavior corresponds to the wide side of the converging–diverging channel, which forms the non-expanding wall of the SERN. The structures are stable when not under these flow conditions and thus lack this modulation.

本文研究了矩形喷嘴在超音速运行过程中的结构响应。本研究中的喷嘴称为单膨胀斜坡喷嘴 (SERN)，喉部纵横比 (TAR) 范围为 6 到 9，设计马赫数为 1.5。在和接近最强的非设计流动条件下，在膨胀不足和过度膨胀的流动状态下，都会观察到尖叫振幅的周期性调制。调制现象的近场压力特征及其频率特性表明，其起源是喷嘴壁结构模式的激发，而不是流体声学现象，如具有斯特劳哈尔数特征的尖叫声。调制行为对应于收敛-发散通道的宽边，它形成了 SERN 的非扩展壁。