刚性壁或刚性单柱附近水下爆炸气泡脉动的数值研究

Numerical study on dynamic behaviors of UNDEX bubble near rigid wall or rigid column

为进一步研究近自由面水下爆炸受到刚性壁、刚性柱影响,气泡呈现出的复杂运动特性,首先基于LS-DYNA有限元软件建立了近自由面和刚性边界下水下爆炸气泡脉动运动数值计算方法,并依据已有经验公式和试验结果对数值方法的有效性进行验证;然后,在真实尺寸的水下爆炸模型基础上,研究了刚性壁、刚性单柱附近水下爆炸气泡总体运动过程、能量释放及射流载荷特性。结果表明:刚性壁与刚性柱附近水下爆炸,气泡收缩阶段在浮力和Bjerknes力共同作用下形成偏向刚性壁(刚性柱)方向的射流,气泡射流时气泡动能、水平位移显著提高,并且脉冲荷载指向刚性边界,相较自由场刚性边界附近脉冲荷载增加,远离刚性边界一侧脉冲荷载降低,其中刚性壁对气泡射流的增强作用明显大于刚性柱;随着比例距离增加,气泡脉动现象趋于自由边界,当气泡与刚性壁距离大于3倍气泡半径、与刚性柱距离大于2倍气泡半径时,刚性边界对气泡脉动的影响基本可以忽略。

To further investigate complex bubble dynamic behaviors under combined action of rigid boundary and free surface,the bubble dynamics near a rigid wall/column was simulated and analyzed using hydraulic-solid coupling based LS-DYNA software.The computational results and experimental results were basically anastomotic,which proved the reliability of numerical method.Based on a large amount of simulation data,the influence of the wall/column on the characters of bubble pulse and the direction of jet were analyzed.The results showed that the bubble jet near a rigid wall/column was inclined to the wall/column.The horizontal displacement and Kinetic energy of the bubble increase clearly near a rigid boundary.The bubble impulsive load increases near a rigid boundary and decreases beyond the rigid boundary.The rigid wall has more influence on the bubble pulse than the rigid co-lumn.The Bjerknes force decreases dramatically as distance from the wall/column to explosive increases.While the standoff distance exceeds the triple of maximum radius,the rigid wall effect on bubble pulse can be neglected.While the standoff distance exceeds the double of maximum radius,the rigid column effect on bubble pulse can be neglected.