Numerical analysis of shear cavitation flow characteristics of convergent-divergent nozzles
CHEN Songping1, LI Wei1,2*, ZHANG Wenquan1, HU Jingning1, YANG Yongfei3, LIU Mingjiang1
1. National Research Center of pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. Institute of Fluid Engineering Equipment Technology, Jiangsu University, Zhenjiang, Jiangsu 212009, China; 3. School of Mechanics Engineering Nantong University, Nantong, Jiangsu 226019, China
Abstract: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.