计及浮力影响的竖直刚性边界附近气泡溃灭动力学特性实验研究

Experimental study on dynamic characteristics of bubble collapse around vertical boundary to buoyancy

气泡的运动形式往往受到边界条件的显著影响,近边界气泡在第一次溃灭后依然具有一定的能量,其运动射流仍可造成结构的损伤。因此,开展相关气泡实验可为近场水下爆炸射流方向的判定与气泡二次脉动带来的舰船毁伤提供参考。为揭示气泡与竖直壁面的相互作用规律,采用实验效果理想的电火花气泡发生装置在减压条件下生成气泡,并使用高速摄像机捕获气泡的膨胀,坍塌,回弹,再次坍塌和迁移过程,对气泡的第二次脉动进行了分析。实验结果显示气泡对两个参数敏感:初始气泡中心到竖直壁面的无量纲距离γw和表示浮力影响的无量纲参数δ。实验揭示了竖直壁面附近气泡的动力学特性,得到壁面效应、气泡的非对称性坍塌和气泡中心迁移随两个敏感参数的变化规律,为相关理论和数值研究提供支持;测量了不同情况下气泡坍塌的角度,发现了明显的变化趋势,利用射流角度的可控性,对清洁刚性表面引入了一种新的思路。

The motion of bubbles is often significantly affected by boundary conditions.There is still a certain amount of energy stored in a near-boundary bubble after the first collapse,and its moving jet can still cause structural damage.Therefore,a related bubble experiment can provide a reference for the determination of the jet direction of the near-field underwater explosion and the damage caused by the secondary pulsation of the bubble.In order to reveal the interaction between the bubbles and the vertical wall,an effective electric spark device was used to generate bubbles under reduced pressure.The expansion,collapse,rebound,re-collapse,and migration of the spark-generated bubbles were recorded by a high-speed camera,and the second pulsation of bubbles was analyzed.The phenomenon depends largely on two dimensionless parameters:dimensionless distanceγw from the initial bubble center to the vertical wall and dimensionless parameterδfor the effect of buoyancy.Experiments reveal the dynamic characteristics of bubbles near vertical walls,and the variation laws of wall effect,asymmetric collapse of bubbles and center migration of bubbles with two sensitive parameters were obtained,which provides support for theoretical and numerical studies.It also provides supports for theoretical and numerical research.In addition,the angles of bubble collapse under different conditions were measured,and the obvious change trend was found.Using the controllability of jet angle,a new idea for cleaning rigid surfaces was introduced.