【摘要】 针对水下低流速蒸汽泡凝结振荡特性，采用VOF模型和双阻力相变模型开展数值模拟计算，分析了入口流速在0.25～1.0 m·s^-1和水温在40～70?C工况下汽泡流动换热特性。研究发现，汽泡夹断过程颈部半径变化可用两个分段幂函数来描述，第二段幂函数指数κ₂随入口流速增加变化显著，从0.87增加到1.27。汽泡夹断脱离时刻内压振荡剧烈，振荡幅度和脱离频率随入口流速增大和水温降低而增大。生长颈缩阶段界面换热系数先增大后减小，脱离溃灭阶段界面换热系数呈指数增长，界面瞬时换热系数最高可达k W·m^-2·K^-1量级。蒸汽泡受力分析表明，颈缩夹断过程压差力和凝结作用力对汽泡振荡起主导作用；随着入口流速和水温的增大，颈缩末期凝结作用力作用凸显，与压差力比值从0.6增大到0.8。更多还原

【Abstract】 Numerical simulations were carried out using the VOF model and two-resistance phase change model. The flow and heat transfer characteristics of steam bubbles were analyzed under conditions of inlet velocities ranging from 0.25 to 1.0 m·s^-1and water temperatures from 40 to70?C. It is found that the variation of the neck radius during the bubble pinch-off process can be described by two piecewise power functions, and the power exponent κ₂ of the second segment increases significantly from 0.87 to 1.27 with the increase of inlet velocity. At the moment of bubble pinch-off and detachment, intense internal pressure oscillations occur, and the oscillation amplitude and detachment frequency increase with increasing inlet velocity and decreasing water temperature.During the growth and necking stage, the interfacial heat transfer coefficient first increases and then decreases; whereas during the detachment and collapse stage, the interfacial heat transfer coefficient grows exponentially, with the maximum instantaneous value reaching the order of k W·m^-2·?C^-1.Force analysis of the steam bubble indicates that the pressure difference force and condensation force play a dominant role in bubble oscillation during the necking and pinch-off process. With the increase of inlet velocity and water temperature, the effect of condensation force becomes prominent in the late stage of necking, and its ratio to the pressure difference force increases from 0.6 to 0.8.更多还原