计及空化效应与自由面羽化破碎的水下爆炸气泡动力学特性研究

Underwater explosion bubble dynamics has significant applications in researches on anti-shock of warship and self-defense with water barrier. This project is aiming to study the interaction of underwater explosion bubble with free surface and submerged structures numerically and experimentally. The main contents of this project are listed as below. ①Underwater explosion bubble dynamics model considering cavitation effect is expected to be established based on the Eulerian finite element method with operator split technique. Combining with the cavitation model and adaptive mesh refinement technique, we are going to study the bubble dynamics near shattered free surface. ②Based on dynamic penalty method, the fluid-structure interaction model of underwater explosion is expected to be established. Then the influence of the cavitation effect on the impact load features of submerged structure and the damage characteristics are going to be studied. ③In this project, the scaled experiments of the break-reclosure of bubble near free surface would be carried out in pressure-reduced container, and the scaled experiments of the shock responses of ship structure subjected to underwater explosion would be carried out in water tank. The numerical models established in this project is going to be validated. This project is aiming at to establish a set of numerical methods for underwater explosion and fluid-structure interaction, which could provide technical supports for researches of anti-shock of warship and self-defense with water barrier.

水下爆炸在舰船抗冲击、水幕反导等领域有重要的应用，本项目拟针对水下爆炸气泡与自由面及水中结构的耦合特性开展数值与实验研究。主要包括：①基于算子分裂的欧拉有限元方法，建立计入空化效应的水下爆炸气泡动力学模型，结合动态网格细分技术，分析计入冲击波空化引起的自由面羽化破碎的水下爆炸气泡与自由面耦合特性研究；②基于动态罚函数方法建立水下爆炸与水中结构流固耦合动力学模型，分析空化对结构湿表面在冲击载荷的影响，及冲击波和气泡联合载荷下舰船局部与总体冲击损伤特性；③分别在减压容器中开展电火花气泡缩比试验和在爆炸水箱中开展水下爆炸对结构冲击损伤特性实验，分析气泡与羽化破碎自由面耦合特性，及水下爆炸载荷下舰船结构损伤特性，并验证本项目建立的数值模型与方法。通过上述研究，本项目旨在建立一套水下爆炸载荷及流固耦合全过程数值方法，为舰船抗冲击、水幕反导等相关领域研究提供技术支撑。

当水下爆炸发生在自由面附近时，产生的冲击波和气泡会与自由面产生复杂的耦合作用，尤其是在自由面产生的空化和自由面破碎等现象影响爆炸冲击对结构毁伤特性，但相关研究较少。本项目针对这一问题，开展了数值与实验研究。首先在欧拉有限元方法的基础上计入总能量守恒，结合多尺度动态网格细分技术，分析了水下爆炸气泡与自由面耦合过程中产生的自由面破裂、破裂后再闭合、完整气泡等多种自由面运动模态的产生机制和力学机理，并给出了其临界参数阈值；其次，通过计入穿透深度在结构湿表面的切向输运，改进了罚函数浸没边界法建立水下爆炸载荷与水中结构流固耦合动力学模型，并分析了水下爆炸冲击波和气泡全过程载荷对水下结构的冲击损伤特性。最后，在爆炸水箱中开展了水下爆炸与自由面耦合特性实验及其对结构冲击损伤特性实验，分析气泡与羽化破碎自由面耦合特性，以及对结构的冲击损伤特性，并验证本项目建立的数值模型与方法。项目成果发表学术论文13篇，其中JCR一区论文9篇，并获得教育部科技一等奖1项（已公示），所建立的分析方法可为水下爆炸水幕反导、舰船抗冲击等提供技术支撑。