Influence of plate wettability and inclination angle on bubble dynamics and acoustics

The interaction between bubbles and solid boundaries is fundamental to optimizing multiphase flow processes. This study experimentally investigates the coupling effects of surface wettability and plate inclination on bubble dynamics and acoustic signatures using synchronized high-speed imaging and hydrophone measurements. Experimental results demonstrate that hydrophobic surfaces promote rapid bubble coalescence into expansive gas films, which subsequently release strip-like secondary bubbles upon detachment. Under inclined conditions, hydrophobic surfaces exhibit significantly higher bubble sliding velocities compared to hydrophilic ones. Acoustically, the sound pressure amplitude during bubble detachment is governed by the competition between edge anchoring and inertial effects. Despite their smaller detachment volume, bubbles on hydrophilic plates generate higher acoustic amplitudes than those on hydrophobic plates, because strong contact line pinning intensifies the neck contraction. Conversely, at steeper inclinations (α = 28°), elevated sliding velocities augment inertial forces, thereby disrupting the neck rupture process and attenuating the acoustic signal. These findings provide new insights into near-wall bubble kinetics and validate passive acoustic monitoring as a robust tool for characterizing bubble–surface interactions.