The physics behind bursting appears to be independent of the material of the bubble. The investigators were surprised to find that the ring effect is still seen with fairly viscous liquids like oil and even in solutions up to 5,000 times as viscous as water. Bird is anxious to study similar popping effects in more exotic materials such as molten glass, lava, and mud.
While understanding how bubbles pop may not offer any near-term applications, the researchers expect that understanding how to create small bubbles from larger ones could one day help inform a variety of fields.
"We have provided a general explanation of why these rings of smaller bubbles can be observed," says co-author Howard A. Stone, Bird's adviser and now the Donald and Elizabeth Dixon Professor in Mechanical and Aerospace Engineering at Princeton. "We think this study highlights one role for larger bubbles in aerosol formation."
It is well known that when small bubbles pop on a liquid surface tiny droplets are ejected upwards. The effect can be readily seen and felt with carbonated sodas. Bubble-mediated aerosols are also relevant to applications in health and climate.
The shooting droplets have been shown to transfer any infectious material as well as dissolved gases and salt from large bodies of water, such as the ocean, into the air. Bubbles over a few millimeters in diameter have tended to be dismissed by researchers as not producing aerosols.
The team's findings, however, may modify this belief as they further uncover how larger bubbles can be a source for these smaller, droplet-creating bubbles.
"So much of cutting-edge research can only be seen with specialized equipment. What I love about this study is that the overall effect can be seen by anyone in their kitchen," concludes Bird. "It's a relatively simple effect and yet you end up with these beautiful patterns and something that is universal."
A smaller, daughter bubble created by the rupture of a larger bubble ruptures on a much faster timescale and also forms a jet. This jet breaks up into micron-sized droplets which are propelled into the atmosphere at speeds exceeding 5 m/s. Therefore the rupture of a centimeter-sized bubble can lead to the aerosolization of dozens of fine droplets into the atmosphere.
(Photo Credit: Courtesy of the Harvard School of Engineering and Applied Sciences)
This is the original movie of the bubble dynamics shown in Fig. 1E-G. The interfacial bubble ruptures, uncovering a dimple on the water surface. The high curvature of this dimple causes a jet to form; since this jet does not have enough kinetic energy to be propelled into the atmosphere it returns to the interface. Yet, around the jet, there is a ring of smaller bubbles formed during the film retraction. One of these daughter bubbles ruptures at 56 ms (left side of movie)
(Photo Credit: Courtesy of Harvard School of Engineering and Applied Sciences)
Instead of simply vanishing, a large bubble disperses into a ring of smaller bubbles (as seen on the surface of a wine glass).
(Photo Credit: Courtesy of Jacy Bird, Harvard School of Engineering and Applied Sciences)
Source: Harvard University