小特征比等温湍流矩形射流的试验研究

An Experimental Study of Rectangular Isothermal Turbulent Jets with a Low Characteristic Ratio

本文通过实验对小特征比(2,4,8)的矩形管道喷口射流作了研究;给出了热线风速仪的测量结果,即近场区的时均特性和湍流特性,包括轴心线上的时均速度衰减和湍流量的变化、射流横截面上的时均速度和湍流量的分布、射流半宽度特性及主副轴的转换特性.文中将所得结果与前人完成的大特征比矩形射流的实验结果做了对比,并进行了有益的讨论.

Rectangular isothermal turbulent jets with a low characteristic ratio of 2, 4, and 8 are investigated experimentally. Measurement results obtained by a hot-wire anemometer of the time average properties and turbulent behaviour in the near field zone have been obtained. The attenuation of the time average velocity Um/Uo along the center line, at X/B≤15 is almost the same for thre jets. However at, X/B≥30, the larger AR is, the lower the decay rate will be. On the jet cross-section, U/Um along two axes are different. The profiles of the half velocity width 2F1/2 and 2Z1/2 are also different.The relative turbulent intensities u'/un and v' /Um along the center line are almost constant inside the potential core zone. Then they increase rapidly till X/B = 10- After that the increasing rate slows down gradually and approaches constant again. The profiles of u'/Um and v' /um along the jet cross-section are saddle-shaped, though different for different jets. A comparison between the results of jets with high characteristic ratio published elsewhere with those obtained by the authors is made.