Experimental and Theoretical Investigations of Edge Tones in High Speed Jets
Experimental and Theoretical Investigations of Edge Tones in High Speed Jets
复制标题
高速喷气机边缘色调的实验和理论研究
DOI：
10.1299/jfst.8.1
复制
发表时间：
2013
影响因子：
0.8
通讯作者：
M. Ibrahim
中科院分区：
文献类型：
--
作者：
M. Ibrahim
对高速射流与楔形边缘的碰撞进行了实验和理论研究。本文对相同水力直径的圆形和方形声速射流进行了研究。已经研究了由于具有不同角度的楔形边缘而产生的边缘色调，具体地说，是10o、20o、60o和180o。实验表明，在麦克风捕获的声信号中同时存在多个不稳定模式。最小宽度被定义为对于要产生的第一音调存在的边缘与喷嘴之间的最小距离。实验表明，在边缘角较小的情况下，最小宽度约为等效二维情况的一半。根据现有的小边角实验数据，提出了主音频率的半经验公式。基于和Ahuja(1)提出的涡片模型的理论结果表明，射流撞击过程中既存在螺旋稳定模式，又存在轴对称稳定模式。主音通常有螺旋稳定模式，这是众所周知的边缘音。其他的音调在文献中被称为撞击音调，并且具有轴对称稳定模式。实验得到的螺旋模和轴对称模的平均Strouhal数与在不同马赫数下计算的相同模的最小频散波的Strouhal数符合得很好。
Experimental and theoretical investigations of the high speed jets impinge on a wedgeshaped edge have been conducted. Sonic circular and square jets of the same hydraulic diameter are examined in the present study. Edge-tones produced due to a wedgeshaped edge having different angles, specifically, 10o, 20o, 60o and 180o, have been investigated. Experiments reveal that several instability modes exist simultaneously in the microphone-captured acoustic signal. The minimum breadth is defined as the minimum distance of the edge from the nozzle exist for the first tone to be generated. Experiments showed that at small edge angle, the minimum breadth is approximately half of its equivalent two-dimension case. Semi-empirical frequency formula for the dominant tone is proposed based on the present experimental data for small edge angles. The theoretical results based on the vortex-sheet model proposed by Tam and Ahuja(1) showed that both helical and axisymmetric stability modes exist during jet impingement. The dominant tone usually has helical stability mode which is the well known edge-tone. Other tones are known as impinging-tones in the literatures and have axisymmetric stability modes. Finally, it has been shown that the experimentally obtained mean Strouhal numbers for helical and axisymmetric modes show good agreement with the Strouhal number of the least dispersive wave of the same mode calculated at various Mach numbers.