基于气泡形态影响的水下气幕对冲击波衰减效果分析

Analysis of underwater shock wave attenuation by air bubble curtain based on bubble shape

气泡帷幕是水下爆炸冲击波防护的重要手段,对其作用机理及技术参数的深入研究对水下爆破安全与应用具有重要意义。采用高速摄影技术对室内小型水下气泡帷幕模型拍摄发现气幕在形成过程和与水下爆炸冲击波相互作用过程中均具有高度非连续性和非均匀性,且气幕区域内气体与液体混杂,界面轮廓复杂多样。在此基础上,考虑气泡形状及界面影响下,通过LS-DYNA有限元软件自带的APDL语言进行编程,实现了在设定的气幕区域内,通过设定气泡直径变化范围及气泡直径之间的最小差异值随机投放一定数量不同直径的气泡来模拟真实气幕中气泡的分布,并通过改变固定区域内气泡个数来模拟不同气压值工况下的气幕效果。分析发现该方法能够更加真实反映气幕在冲击波防护过程中的防护机理,随着单位区域内气泡数量的增大,防护效果越明显,但当气泡数量达到一定数量后气幕整体连续性及稳定性基本固定,防护效果也趋于稳定。

Bubble curtain is an important means for protection against underwater explosion shock wave.It is of great significance to study the mechanism and technical parameters of bubble curtain regarding the safety and application of underwater blasting.By using high-speed photography technology and video framing processing technology,indoor small underwater bubble curtain model is photographed and analyzed.It is found that the gas curtain is highly discontinuous and inhomogeneous in both the formation process and the interaction process with the underwater explosion shock wave.The gas and liquid are mixed in the air curtain area,and the interface contour is complex and diverse.Air displacement will directly affect the quality of the air bubble curtain.The larger the air displacement,the better the continuity and quality of air curtain.On this basis,considering the influences of bubble shape,interface,and gas-liquid coexistence,programming is carried out through the APDL language that comes with the LS-DYNA finite element software.By setting the variation range of bubble diameter and the minimum difference between bubble diameters,a certain number of bubbles of different diameters are randomly positioned to simulate the bubble distributions in the real air curtain.The air curtain quality under different gas source pressure can be simulated by changing the number of bubbles in the set air curtain area.It is found that this method can better reflect the protection mechanism of air curtain against the shock wave.Comparing the protective performance of air curtain with different bubble numbers on the same shock wave,it shows that the protective performance increases with the increase of bubble density.However,when the number of bubbles reaches a threshold number,the overall continuity and stability of the air curtain are basically fixed,and the protection effect tends to be stable.