高速旋转小球入水空泡特性数值模拟

Numerical simulation investigation on water-entry cavity of high-speed spinning sphere

摘要:

为了深入研究旋转体入水空泡特性, 采用VOF均值多相流模型、k-ω湍流模型以及动网格技术, 开展了低弗劳德数条件下高速旋转小球入水过程空泡特性的数值模拟研究.分析已公开发表的关于运动体入水数值仿真的相关论文, 总结了入水数值模拟的最优参数选择, 建立了适用于高速旋转小球入水数值模拟方法.开展不同入水速度和比重的小球入水过程的数值模拟, 对比分析了入水空泡的形成、发展、闭合和溃灭的演化过程.数值计算结果表明:高速旋转小球在入水深度0.25d范围内出现逆升力偏移现象, 逆升力偏移距离随小球速度和比重的增加而减小; 逆升力的大小与入水速度成反比, 而与比重无关.相同比重的小球, 不同入水速度的轨迹相似; 速度相同的小球, 比重越大的轨迹曲率较小.高速旋转小球入水空泡依次发生纵向闭合和横向闭合的二次闭合的现象, 且入水速度越大, 纵向闭合越明显.空泡闭合深度、空泡最大直径以及尾空泡直径均随着速度和比重的增加而增大, 且速度变化产生的影响更加明显.

Abstract:

Water-entry cavities of high-speed spinning sphere (HSS) were investigated numerically based on the volume of fluid (VOF) multiphase flow model, the k-ω model and dynamic grid technique.After analyzed and compared the published papers about the water entry, the optimum numerical models were selected, and a numerical simulation system was established suitable for HSS.The evolutionary process of cavities induced by water-entry HSS with different velocity and specific weight was discussed.The reverse lift offset phenomenon was detected during water-entry process within the depth of 0.25d.The trajectories of water-entry HSS with identical specific weight but different velocities are similar in the initial stages of entry.And the curvature of trajectories of those with larger specific weight but identical velocity gets smaller.The twice-closure phenomenon, vertical-closure and transverse-closure, was discovered during the water entry process.The closure depth, the maximum diameter and the diameter of tail-cavity increase dramatically with larger velocity, and are also affected by the specific weight.