垂直汇流中空化长度的脉动

Cavitation Length Pulsation In Vertical Intersection Flows

超空穴的重要特征之一是其空化长度的脉动。本文用摄影法,对垂直汇流旋涡空化模型,在流速为16.2m/s、21.4m/s、24.4m/s和28.8m/s四个流速下,随机地记录了约1200个空化长度。应用Kolmogolov方法系统地分析了该模型超空穴空化长度的统计特征和分布规律,主要有:表征空化长度的均值,表征空化脉动的均方差和空化长度的概率分布规律。同时,本文还分析了控制超空穴空化长度主要的水力参数。对超空穴及其空蚀的研究有参考作用。

The length pulsation of super-cavitation is one of the important characteristics of super-cavitation. By means of photograph, about 1200 lengths have been randomly recorded for the vortex cavitation model in vertical intersection flows when velocities are 16.2m/s, 21.4m/s, 24.4m/s and 28.8m/s respectively. The statistical characteristics and distributive rules of them for this model,mean value E(ξ),mean square difference D(ξ)and probability statistical distributive rules of the super-cavitation lengths L,are analysed systematically with Kolmogolov's method in this paper. Meanwhile, the main hydraulic parameters controlling those lengths are analysed. The following conclusions may be drawn:1.The lengths of super-cavitation are related closely to the tailpart cavitation parameter at, not the model cavitation parameter at or flow velocity V'∞.2.The relationship between L and σt may be expressed as equation (9), and L varies linearly with σt if σt=0.63-0.82.3. Statistical results indicate that the probability distributive rules satisfy normal, lognor-mal and extreme value type I distributions if α= 0.05, but their levels are not same. They are 25.0%, 20.8% and 54.2% respectively, i.e., extreme value type I is the best one.