Interaction of cavitation bubbles with a free surface

Abstract

The motion of single-and two-cavitation bubbles generated by laser beams directly beneath a free surface is studied experimentally, using high-speed photography, and theoretically using the highly accurate boundary integral method. Favorable comparisons of bubble shape history and centroid motion are observed while the numerical calculations provide information on the pressure field surrounding the bubbles. A range of responses, including the null impulse state, is obtained for the two bubbles depending on the bubble size ratio and the interbubble and bubble-free surface distances, although in all cases reported in this article, the bubble nearest the free surface yields a high-speed liquid jet directed away from the free surface. It is also found that when the free-surface-bubble interaction is strong, a fast free-surface spike is formed for both the single-and two-bubble cases.

The inner world of a collapsing bubble

“…5 Following the impact, the bubble breaks into two parts as the vapor pocket entrained by the jet is separated from the main toroidal bubble. 6 At the moment of collapse of the "main" torus, a stronger set of shock waves is emitted (Figure 2, lower row), and when reflected from the free surface as a rarefaction wave, it results in tension in the liquid and hence excites nearby small bubbles (Figure 1(e)). 7 After the individual collapses of the two separate vapor cavities, an elastic rebound bounces off the violently compressed bubble contents forming a shape reminiscent of an upside-down mushroom cloud.…”

Spray and microjets produced by focusing a laser pulse into a hemispherical drop

“…Work by Blake and Gibson 13 studied cavitation bubbles near a free surface showing jetting. Robinson et al 14 further studied, both experimentally and numerically, the interaction of two closely spaced cavitation bubbles next to a free surface. These are transient laser-produced cavitation bubbles.…”

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.…”