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紊流射流规律是航空、宇航及一般工程所关注的重要问题。激光多卜勒风速仪系统(LDA)在当前是极先进的测速工具。本文总结了用LDA对厚唇喷管的亚音自由射流和同轴自由射流以及超临界自由射流流场进行大规模实验研究中积累的测量经验,并介绍了一些典型的测量结果。经验表明,由于紊流射流涉及很宽的速度和紊流度范围,还涉及冲波的作用,现象很复杂,故影响LDA测量效果的因素相当多。测量中必须精心组织测量过程,正确施加散射粒子,恰当选用频移、激光束夹角及高低通滤波,才能获得满意的结果。
Turbulent jet law is an important issue of concern to aviation, aerospace and general engineering. The laser Doppler anemometer system (LDA) is a very advanced speed measurement tool today. In this paper, we summarize the experience gained by LDA in large-scale experimental study of the free-falling and free-radical jets of thick lip nozzles and the flow field of supercritical free jets. Some typical results are also presented. Experience shows that due to turbulent jet involving a wide range of velocity and turbulence, but also involves the role of the red wave, the phenomenon is very complicated, so the impact of LDA measurement results quite a number of factors. Measurement must carefully organize the measurement process, the proper application of scattering particles, the appropriate choice of frequency shift, laser beam angle and high and low pass filter, in order to obtain satisfactory results.