Jetting and shear stress enhancement from cavitation bubbles collapsing in a narrow gap

Acoustic-driven Oscillations of a Bubble in a Narrow Gap

“…The direction of the resulting jet(s) depends on the height of the gap (nondimensional ) and the axial position of the bubble inside the narrow gap (off-centre distance ). Although the presented geometry is relatively simple, we must stress that it has significant implications for realistic applications, for example in ultrasonic cleaning where the bubble activity is known to produce strong shear forces responsible for removing surface contamination [8][9]23] and in microfluidic applications for mixing and actuation [24], where the number of jets correlates with the number of boundaries confining the bubble [25]. Through careful choice of the acoustic driving and fluid properties, the desired dynamic behaviour to suit the application can be achieved.…”

“…This high resolution is required to sufficiently resolve the bubble at its minimum volume. Existing studies on the influence of confinement on bubble dynamics assume an undriven, initially small, bubble at high pressure to match laser-induced or spark-generated cavitation bubbles in experiments [8][9][10]20]. The initial conditions in this study are the static equilibrium conditions.…”

“…The authors acknowledge the use of the Scientific Computing Research Technology Platform, and associated support services at the University of Warwick UK, in the completion of this work. The first author is indebted to Dr. Indrajit Chakraborty for interesting discussions on the subject and the authors of [9] for exchanges regarding the OpenFOAM solver.…”

“…Bubble oscillations in narrow gaps have received attention only recently [8][9][10], but none of these studies considered acoustic cavitation dynamics confined by rigid boundaries. To the authors' best knowledge, this study is the first to address this knowledge-gap.…”

Cavity collapse near slot geometries

“…The majority of prior experimental research has focused on the jet dynamics near simple flat boundaries (Benjamin & Ellis 1966; Plesset & Chapman 1971; Kucera & Blake 1990; Dijkink & Ohl 2008; Supponen et al 2016) or cases with limited complexity such as axisymmetric boundaries (Tomita et al 2002) or parallel boundaries (Han et al 2018; Gonzalez-Avila et al 2020). Although understanding how bubbles behave near simple geometries is important, in reality geometries have many more complex features such as corners, indentations, slots and surface imperfections.…”