Growth and collapse of cavitation bubbles near a curved rigid boundary

Abstract

Laser-induced cavitation bubbles near a curved rigid boundary are observed experimentally using high-speed photography. An image theory is applied to obtain information on global bubble motion while a boundary integral method is employed to gain a more detailed understanding of the behaviour of a liquid jet that threads a collapsing bubble, creating a toroidal bubble. Comparisons between the theory and experiment show that when a comparable sized bubble is located near a rigid boundary the bubble motion is significantly influenced by the surface curvature of the boundary, which is characterized by a parameter ζ, giving convex walls for ζ < 1, concave walls for ζ > 1 and a flat wall when ζ = 1. If a boundary is slightly concave, the most pronounced migration occurs at the first bubble collapse. The velocity of a liquid jet impacting on the far side of the bubble surface tends to increase with decreasing parameter ζ. In the case of a convex boundary, the jet velocity is larger than that generated in the flat boundary case. Although the situation considered here is restricted to axisymmetric motion without mean flow, this result suggests that higher pressures can occur when cavitation bubbles collapse near a non-flat boundary. Bubble separation, including the pinch-off phenomenon, is observed in the final stage of the collapse of a bubble, with the oblate shape at its maximum volume attached to the surface of a convex boundary, followed by bubble splitting which is responsible for further bubble proliferation.

Dynamics of laser-induced bubble pairs

“…In particular, directed fluid transport over short distances or micro-manipulation of adjacent objects are attractive perspectives. While solid, free, elastic or composite interfaces and bubble manipulation with acoustic or shock waves might be considered as a means of control of individual jetting bubbles (Chahine 1977;Blake & Gibson 1981;Gibson & Blake 1982;Blake et al 1986;Blake, Taib & Doherty 1987;Shima et al 1989;Brujan et al 2001a,b;Robinson et al 2001;Tomita et al 2002;Wolfrum et al 2002Wolfrum et al , 2003Ohl et al 2006;Wang & Blake 2010, their use can be problematic owing to the introduction of additional constraints and the need for proper placement. Generation of a single asymmetric bubble (Lim et al 2010) or of a bubble pair (Lauterborn 1974;Lauterborn & Vogel 1984;Lauterborn & Hentschel 1985;Testud-Giovanneschi, Alloncle & Dufresne 1990;Tomita, Shima & Sato 1990;Blake et al 1993;Jungnickel & Vogel 1994;Tomita, Sato & Shima 1994;Fong et al 2009;Sankin, Yuan & Zhong 2010) with predetermined jetting behaviour by means of optical breakdown in the bulk of transparent liquids appear as a less invasive and more versatile tool for control and optimization of jet properties.…”

Cavitation Bubble Dynamics inside Liquid Drops in Microgravity

“…Fundamental understanding requires studies of single bubbles in different liquid geometries, since bubble dynamics strongly depends on nearby surfaces by means of boundary conditions imposed on the surrounding pressure field [1,6]. Recent investigations revealed interesting characteristics of bubbles collapsing next to flat [7] and curved [8] rigid surfaces or flat free surfaces [9,10]. It is thus a promising idea to study bubbles inside spherical drops and probe their interaction with closed spherical free surfaces.…”

Asymmetric oscillation of adherent targeted ultrasound contrast agents

“…18,21 For a bubble with an initial radius of 5 microns and wall velocity of 12 m/s, in a microvessel with a diameter of 200 microns, the ratio of (a-b)/a was estimated to be ∼2.5%, where a and b are the semimajor and semiminor axes of an ellipse, respectively. 22 In our experimental study in a 200 micron microvessel, bubbles were adherent to the boundary rather than located in the center of the microvessel, and the acoustic pressure used resulted in a higher maximum wall velocity, estimated to be on the order of 50 m/s at 240 kPa.…”