On the dynamics of a collapsing bubble in contact with a rigid wall

Abstract

This work reveals that the dynamic response of a spherical cap bubble in contact with a rigid wall depends on the effective contact angle at the instant prior to collapse. This parameter allows us to discriminate between two regimes in which the mechanisms of interaction between the collapsing bubble and its surrounding medium differ significantly: when the contact angle is smaller than $90^{\circ }$ , a classical jet directed towards the wall is observed, whereas if the initial contact angle is larger than $90^{\circ }$ , an annular re-entrant jet parallel to the wall appears. We show that this change of behaviour can be explained using the impulse potential flow theory for small times, which shows the presence of a singularity on the initial acceleration of the contact line when the contact angle is larger than $90^{\circ }$ . Direct numerical simulations show that although viscosity regularises the solution at $t > 0$ , the solution remains singular at $t=0$ . In these circumstances, numerical and experimental results show that the collapse of flat bubbles can eventually lead to the formation of a vortex ring that unexpectedly induces long-range effects. The role of the bubble geometry at the instant of maximum expansion on the overall collapse process is shown to be well captured by the impulse potential flow theory, which can be generalised easily to other bubble shapes. These results may find direct application in the interpretation of geophysical flows as well as the control and design of biomedical, naval, manufacturing and sonochemistry applications.

Single cavitation bubble dynamics in a stagnation flow

“…(2012) and Aganin, Kosolapova & Malakhov (2019), and was later shown to occur for axisymmetric cap-shaped bubbles in simulations and experiments by Saini et al. (2022). Here, a high-pressure region below the bubble forms that accelerates a liquid jet flow away from the surface.…”

Cavitation bubble dynamics inside a droplet suspended in a different host fluid

“…Bubble dynamics in an infinite/semi-infinite liquid domain has been widely and extensively studied in the literature, including interactions with rigid walls (Hsiao et al 2014;Brujan et al 2018;Saini et al 2022;Zeng, An & Ohl 2022;Zhang et al 2023a), a water-air free surface (Kang & Cho 2019;Bempedelis et al 2021;Saade et al 2021;Cerbus et al 2022), elastic boundaries (Brujan et al 2001;Klaseboer & Khoo 2004b), fluid-fluid interfaces (Klaseboer & Khoo 2004a;Orthaber et al 2020), adjacent bubbles (Han et al 2016;Tomita & Sato 2017;Luo, Xu & Khoo 2021), suspended particles (Poulain et al 2015;Ren et al 2022) and more. Of particular interest are the bubble collapse patterns and jetting behaviours in different situations.…”

“…2018; Saini et al. 2022; Zeng, An & Ohl 2022; Zhang et al. 2023 a ), a water–air free surface (Kang & Cho 2019; Bempedelis et al.…”

Direct numerical simulations of microlayer formation during heterogeneous bubble nucleation

“…Fuster, Pham & Zaleski (2014) discussed the stability of bubbly liquids from a free energy perspective and extended these ideas to clusters of bubbles. Saini, Zaleski & Fuster (2021) and Saini (2022) discussed the effect of wall boundary condition on the stability of spherical cap shaped nuclei attached to a rigid wall and showed that pinning can stabilize the bubble nuclei.…”

“…There are several other studies available in the literature, but there is no common consensus for the structure and the growth of the microlayer (Jung & Kim 2018;Zou, Gupta & Maroo 2018;Sinha, Narayan & Srivastava 2022). In the cavitation process, microlayer formation influences the bubble shape at the maximum volume, which is an important parameter that afterwards governs the collapse dynamics (Saini et al 2022).…”