Henderson Brenda
Mechanical Engineering Department, Kettering University, Flint, Michigan 48504-4898, USA.
J Acoust Soc Am. 2002 Feb;111(2):735-47. doi: 10.1121/1.1436069.
An experimental investigation into the sound-producing characteristics of moderately and highly underexpanded supersonic impinging jets exhausting from a round convergent nozzle is presented. The production of large plate tones by impingement on a square plate with a side dimension equal to 12 nozzle exit diameters is studied using random and phase-locked shadowgraph photography. Discrete frequency sound is produced in the near-wall region of the jet when a Mach disk occurs upstream of the standoff shock wave. Tones cease when the plate distance is approximately 2.2 free-jet cell lengths and the first and second shock waves are located in the free-jet positions. The production of impulsive sound appears to be associated with the collapse of the standoff shock wave during a portion of the oscillation cycle. Results from unsteady plate-pressure measurements indicate that plane-wave motion occurs in the impingement region and a secondary pressure maximum is observed on the plate adjacent to the flow region where sound appears to originate.
本文对从圆形收敛喷嘴排出的适度欠膨胀和高度欠膨胀超声速冲击射流的发声特性进行了实验研究。使用随机和锁相阴影摄影技术，研究了冲击在边长等于12个喷嘴出口直径的方形平板上时产生的大板音调。当马赫盘出现在驻定激波上游时，在射流的近壁区域会产生离散频率的声音。当平板距离约为2.2个自由射流单元长度且第一和第二激波位于自由射流位置时，音调停止。脉冲声的产生似乎与驻定激波在振荡周期的一部分期间的坍塌有关。非稳态平板压力测量结果表明，在冲击区域会出现平面波运动，并且在与声音似乎起源的流动区域相邻的平板上观察到二次压力最大值。
