缩放型喷嘴空化流动特性的数值分析

为研究空化射流结构及剪切空泡的形成演化,文中采用RANS-LES混合模型方法对一种缩放型喷嘴的空化水射流进行数值模拟计算,对比分析了不同扩张角喷嘴对射流流场的影响以及空泡初生阶段其形态、速度、湍动能等物理量的变化规律.计算结果发现:喷嘴扩张角对空化射流影响较大,当扩张角为60°时其空化性能更优;由于空化射流速度非常高,射流剪切层内存在较大的速度梯度,两侧流体发生频繁的能量交换并产生许多旋涡结构;空化现象最早发生在喷嘴喉管处并逐渐向扩张段及喷嘴出口附近运动发展,空化程度不断增大,不同时刻径向截面内的各参数均沿轴心对称分布,空泡形态呈圆环状,并随着时间推移圆环面积逐渐增大.研究结果对于提高空化水射流性能、拓宽空化水射流应用范围、揭示空化水射流特性等方面具有一定的应用价值及指导作用.

Numerical analysis of shear cavitation flow characteristics of convergent-divergent nozzles

In order to study the structure of the cavitation jet and the evolution of the formation of shear cavitation bubbles, the RANS-LES mixed method was used to numerically calculate the cavitation water jet with a scaled nozzle. The effects of different diffusion angle nozzles with different expansion angles on the jet flow field are compared and analyzed, as well as the patterns of variation of physical quantities such as vacuole morphology, velocity and turbulent kinetic energy during the initial stage of cavitation growth. The results showed that the nozzle expansion angle has a significant effect on the ca-vitation jet, and cavitation performance is better when the diffusion angle is 60°. Because of the very high cavitation jet velocity, there was a large velocity gradient within the jet shear layer, and the fluids on both sides exchanged energy and generated many vortex structures. The cavitation phenomenon first occurred at the nozzle throat and gradually moving and developing towards the diffusion section and near the nozzle outlet, and the degree of cavitation was increasing. At different moments, in the radial section of the parameters were symmetrically distributed along the axis. The vapor pattern is circular ring and the area of the circular ring gradually increased in size over time. The research results have certain application value and guiding effect for improving the performance of cavitation water jet, broadening the application range of cavitation water jet, and revealing the characteristics of cavitation water jet.