The response of underwater structures to a near-field explosion is coupled with the dynamics of the explosion bubble and the surrounding water. This multiphase fluid-structure interaction process is investigated using a model problem that features the yielding and collapse of a thin-walled aluminum cylinder. A recently developed computational framework that couples a compressible fluid dynamics solver with a structural dynamics solver is employed. The fluid-structure and liquid-gas interfaces are tracked using embedded boundary and level set methods. The conservation law across the interfaces is enforced by solving one-dimensional bimaterial Riemann problems. The initial pressure inside the explosion bubble is varied by two orders of magnitude in different test cases. Three different modes of collapse are discovered, including an horizontal collapse (i.e. with one lobe extending towards the explosive charge) that appears counterintuitive, yet has been observed in previous laboratory experiments. Because of the transition of modes, the time it takes for the structure to reach self-contact does not decrease monotonically as the explosion magnitude increases. The flow fields, the bubble dynamics, and the transient structural deformation are visualized to elucidate the cause of each collapse mode and the mode transitions. The result suggests that the pressure pulse resulting from the contraction of the explosion bubble has significant effect on the structure's collapse. The phase difference between the structural vibration and bubble oscillation influences the structure's mode of collapse. Furthermore, the transient structural deformation has clear effect on the bubble dynamics, leading to a two-way interaction. A liquid jet that points away from the structure is observed. Compared to the liquid jets produced by bubbles collapsing near a rigid wall, this jet is in the opposite direction.

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近场水下爆炸气泡结构相互作用的计算分析

水下结构对近场爆炸的响应与爆炸气泡和周围水体的动力学相结合。使用以薄壁铝圆柱体的屈服和坍塌为特征的模型问题研究了这种多相流-固耦合过程。采用了最近开发的计算框架，该框架将可压缩流体动力学求解器与结构动力学求解器相结合。使用嵌入式边界和水平集方法跟踪流固和液气界面。通过解决一维双材料黎曼问题来强制执行跨越界面的守恒定律。在不同的测试案例中，爆炸气泡内的初始压力有两个数量级的变化。发现了三种不同的坍塌模式，包括看似违反直觉的水平坍塌（即一个波瓣向炸药装药延伸），但在以前的实验室实验中已经观察到。由于模式的转换，结构达到自接触所需的时间不会随着爆炸强度的增加而单调减少。流场、气泡动力学和瞬态结构变形被可视化，以阐明每种坍塌模式和模式转换的原因。结果表明，爆炸气泡收缩产生的压力脉冲对结构的倒塌有显着影响。结构振动和气泡振荡之间的相位差影响结构的倒塌模式。此外，瞬态结构变形对气泡动力学有明显影响，导致双向相互作用。观察到指向远离结构的液体射流。与气泡在刚性壁附近坍塌产生的液体射流相比，这种射流的方向相反。