运载工具喷水推进跌落射流气-液两相流动特性和空气夹带机理研究

Study on Gas-Liquid Two-phase Flow Characteristics and Air Entrainment Mechanism of Water-jet Propulsion Plunging Jet of Delivery Vehicle

采用数值模拟与试验相结合的方法,考虑喷口几何形状、射流速度和跌落高度等因素,研究跌落射流气-液两相流动特性和空气夹带机理,分析跌落射流初始砰击过程和空腔的非稳态演化,讨论流场压力和速度的分布规律。研究结果表明:自由液面、跌落液柱、空腔、气泡和液滴等相间界面时空变化复杂;根据自由液面下方的气泡数目、分布和形成间隔,可确定无夹带、开始夹带、间歇夹带和连续夹带4种空气夹带模式;各影响因素的耦合会改变气泡羽流的穿透特征。根据射流跌落高度和射流速度建立了空气夹带图谱。研究成果可为提高运载工具的喷水推进效率和进行结构优化设计提供技术支撑。

Numerical simulation and experimental research are used to study the plunging water jet,and influencing factors such as nozzle shape,exit velocity,plunging height,and angle are carefully considered.The gas-liquid two-phase flow characteristics and air entrainment mechanism,initial impact process and unstable evolution of the cavitation,and distribution of the pressure and velocity in the flow field are studied.The results demonstrate that the multiphase interfaces,such as free surface,plunging liquid column,cavitation,bubbles,and droplets appear complex spatial and temporal changes.Four air entrainment modes(non-entrainment,incipient entrainment,intermittent entrainment,and continuous entrainment)can be distinguished based on the quantity and distribution of bubbles,and the interval beneath the free surface where bubbles are formed.The penetration characteristics of the bubble plume are analyzed,and the flowing map and entrainment regimes depending on plunging height and jet velocity are determined.The research will provide technical support to the improvement of the efficiency of water-jet propulsion and optimal structure design of delivery vehicles.