AI 中文总结
研究超纯水中垂直壁附近可变形气泡上升，探讨壁前缘位置对其近壁动力学的影响。通过两种配置实验，发现壁前缘位置影响气泡动力学模式转变及频率，表明气泡动力学受多种因素制约。
AI 中文摘要
本研究调查了超纯水中靠近垂直壁上升的可变形气泡，重点关注壁前缘位置如何影响其近壁动力学。考虑了两种配置：一种是从气泡注入点下方11 - 25个气泡直径处延伸的壁，使气泡在边界的持续影响下上升；另一种是壁前缘位于注入器上方144毫米处，对应约80 - 180个气泡直径，使气泡在进入壁边界区域之前达到其终端速度。结果表明，壁前缘位置影响从周期性弹跳（PB）到弹跳 - 翻滚 - 逃逸（BTE）动力学的转变以及PB模式内的反弹频率。当壁前缘位于下游时，BTE的起始发生在较小的气泡尺寸处，同时对应较低的邦德（$Bo$）、伽利略（$Ga$）和雷诺（$Re$）数。在低邦德数下，斯特劳哈尔数（$St$）在两种配置中都呈现类似下降趋势，但在（$Bo \gtrsim 0.15$）时两种行为不同。对于PB模式，当壁从注入器延伸时，$St$接近约$St\simeq0.014$的恒定值，而下游壁配置测量到的值要低得多。在后一种配置中观察到的较大反弹幅度和较长返回阶段导致频率较低。这些发现表明，气泡动力学不仅取决于传统控制参数和壁间距，还取决于壁几何形状和相关的预相互作用气泡流体动力学历史。
英文摘要
This work investigates deformable gas bubbles rising near a vertical wall in ultrapure water, focusing on how the position of the wall leading edge affects their near-wall dynamics. Two configurations are considered: (i) a wall extending from 11--25 bubble diameters below the bubble injection point, so that the bubble rises under the continuous influence of the boundary; and (ii) a wall whose leading edge is located 144 mm above the injector, corresponding to approximately 80--180 bubble diameters, allowing the bubble to reach its terminal velocity before entering the wall-bounded region. The results show that the wall leading-edge position influences both the transition from periodic bouncing (PB) to bouncing--tumbling--escaping (BTE) dynamics and the rebound frequency within the PB regime. When the wall leading edge is placed downstream, the onset of BTE occurs at smaller bubble sizes, corresponding simultaneously to lower Bond ($Bo$), Galilei ($Ga$), and Reynolds ($Re$) numbers. The Strouhal number ($St$) follows a similar decreasing trend in both configurations at low Bond numbers, but the two behaviours diverge for ($Bo \gtrsim 0.15$). For the PB regime, when the wall extends from the injector, $St$ approaches an approximately constant value of $St\simeq0.014$, whereas substantially lower values are measured for the downstream-wall configuration. The larger rebound amplitudes and longer return stages observed in the latter configuration account for lower frequencies. These findings indicate that the bubble dynamics depend not only on the conventional control parameters and wall separation, but also on the wall geometry and the associated pre-interaction bubble hydrodynamic history.
Comments20 pages, 5 figures
