船舶结构边界条件下多气泡脉动特性

Multi-bubble pulsation characteristics under boundary conditions of ship structure

为研究多气泡在船舶壁面结构附近的脉动特性,采用400 V水下低压放电生成气泡技术,通过超高速摄像机记录水下气泡的脉动过程。在气泡距壁面适当距离下,在水平壁面下方水平布置或垂向布置2个气泡,在V型结构壁面两侧对称水平布置2个气泡,在不同的气泡与壁面距离、2个气泡间距下分析多气泡耦合脉动特性。试验结果表明:不同边界条件下2个气泡的耦合特性不同;水平壁面下方垂向布置的2个气泡融合后出现颈缩现象,产生的射流穿透气泡后冲击到壁面,壁面承受冲击力;水平壁面下方水平布置的2个气泡融合后产生斜向上的射流,射流相撞,最终冲击到壁面上,对壁面造成损伤;V型结构壁面下水平布置2个气泡,耦合后产生指向对方和V型结构的射流,射流在气泡中间相撞,气泡断裂,射流对V型结构的冲击较小。

To study the pulsating characteristics of multiple bubbles near the wall of a ship structure,a technique involving underwater low-voltage discharge at 400 V to generate bubbles is used.The pulsating process of underwater bubbles is recorded with a high-speed camera.By placing two bubbles either horizontally or vertically beneath a horizontal wall at an appropriate distance from the wall,and symmetrically arranging two bubbles horizontally on both sides of a V-shaped wall surface,the coupled pulsating characteristics of multiple bubbles are analyzed at different distances from the wall and bubble space.Experimental results show that the coupling characteristics of two bubbles vary under different boundary conditions.When two bubbles are vertically arranged beneath a horizontal wall,neck constriction occurs after bubble fusion,leading to a jet penetrating through the bubble and impacting the wall,causing an impact force on the wall.Fusion of two bubbles arranged horizontally beneath a horizontal wall results in an obliquely upward jet,which collides and ultimately impacts the wall,causing damage.When two bubbles are horizontally arranged beneath a V-shaped wall surface,the coupling generates jets directed towards each other and the V-shaped structure.The jets collide between the bubbles,causing bubble rupture and resulting in less impact on the V-shaped structure.