水下爆炸气泡诱导自由面运动的滞后效应研究

When a charge explodes near a free surface, a water column spreading upward would be formed, which is widely used in the fields of plume anti-missle. The rise and collapse of the water column generates a free surface wave which propagates radially. This water wave would impact the warship structures and the buildings which are far beyond the influence of the shock wave and bubble impulsation generated by underwater explosion. Its mechanism is the lagging motion of the free surface induced by the bubble. Current studies mainly focus on the effects of the free surface to the bubble motion instead of the lagging motion of the free surface. In this project, the 3D Boundary Element model which takes the fluid’s weak compressibility into account is used to simulate the formation and evolution of the free surface. The laser beam is used to generate a bubble and in order to obtain a bubble with high sphericity, a concave mirror is used in the fluid field to reflect and focus the beam. In this way, a bubble with high sphericity will be formed. With this method, bubble and free surface motion under different buoyancy parameter, distance parameter and multi-bubble would be studied in a vacuum water tank. Real underwater charge explosion experiment would be conducted based on the analysis of the data of the laser generated bubble in a vacuum tank. The numerical model is finally validated through experimental result. The mechanism of the lagging effect of the free surface is then explored. The main contents of this project includes: 1) the numerical model of the interaction between a bubble and the free surface in weak compressible fluid; 2) the study of the mechanism and motion features of the bubble bursting at the free surface; 3) the features of water wave induced by the fall of the water column and the wave-body interaction; 4) the experimental study on the motion of the free surface induced by a bubble.

药包近水面爆炸会形成向上喷射的水柱，在水幕反导中有重要应用；水柱升高和跌落会形成朝向远处传播的波浪，可能对冲击波和气泡影响范围之外的浮体及海上建筑物造成破坏。本项目着眼于药包近水面爆炸诱导自由面滞后运动的基本现象，在已有研究基础上，建立计入流场弱可压缩性的三维边界元数值模型，研究自由面破裂、水柱喷射、兴波和波-物流固耦合运动现象，分析气泡诱导不同自由面现象的形成及演化机理。基于激光聚焦生成气泡技术，采用在水箱中安置凹面反光镜反射平行激光的方法获得高球度气泡，在减压水箱中模拟不同浮力和距离参数情况下自由面运动特性，验证数值模型有效性。在此基础上，探索气泡诱导自由面滞后效应的机理。本项目的主要研究内容包括：1）弱可压缩流场中气泡与自由面相互作用数值模型；2）气泡在自由面处破裂的机理及运动规律研究；3）水柱跌落兴波传播特性及其与结构流固耦合特性研究；4）气泡诱导自由面滞后运动机理性实验研究。

在近自由面爆炸的药包，会推动水面形成向上的水柱，其升高和跌落会向远处传播波浪，这可能会对药包产生的冲击波和气泡影响范围之外的浮体及海洋结构物造成破坏。立足于药包近水面爆炸诱导自由面滞后运动的基本现象，本项目在前人的研究基础上，建立了弱可压缩流场中气泡与开域自由面相互作用的三维边界元数值模型和弱可压缩流场中环状气泡运动的三维边界元数值模型，形成了三维气泡在自由面处破裂的准则与计算方法和维持三维计算过程数值稳定的数值处理方法。此外，还研究了气泡诱导自由面兴波及其传播规律，确定了基于激光激励的高球度气泡实验方法，获得了水下爆炸气泡兴波运动的实验数据。项目建立的数值模型在海洋资源勘探方面具有应用前景，同时，其在水幕反导、爆炸兴波场预报等方面也具备潜在的应用价值。在本项目支持下，在Applied Ocean Research、Physics of Fluids、Ocean Engineering等期刊上发表学术论文16篇。此外，还获得国家技术发明二等奖（排名第四），国防科技进步奖一等奖（排名第三），黑龙江省科技进步二等奖（排名第二）。