Researchers at Tokyo Metropolitan University have revealed how liquid foams fall when viewing individual collapse events with high-speed video microscopy. He found that the cracks in the films lead to a liquid-liquid front that broadens the original film boundary, changes its shape, and leaves a small drop, which hits and breaks other films.
His observations and physical models provide important insights into how to make foam more or less resistant to collapse.
Understanding how the fall of foam is a serious business. How to make sure that there is enough time to put out the flames to extinguish the flames, clean the toxic froths in the sea and rivers, or just get up right on the cake, how the foam material can fall. Help to keep the foam for longer or disappear quickly.
Prof. of Tokyo Metropolitan University. A team led by Ri Kurita is carrying out high-speed video microscopy experiments on liquid foam. By generating trapped foam between two thin, transparent plates, they have direct access to the full range of complex phenomena that occur when they collapse.
In previous work, he showed that after the breakdown of individual films there is an important way through the origin of the skirmishes.
These droplets fly at a high speed and break up other surrounding films, creating a cascade of rupture that breaks the foam. Nevertheless, it was not yet known how the droplets were formed. Crucially, it was not clear when the droplets were formed and when they were not.
Now, teams have begun to uncover the complex mechanisms behind how these drops are made. When an initial crack is formed in a film, the film recurs and leaves a dubbing line of liquid, where the original film was the border, called the released vertical plateau boundary (RVPB). While it stumbles, there is accumulation of liquid in the center of the RVPB. When another crack occurs in the rest of the film, a recurring line of liquid is created, which sweeps the RVPB.
Interestingly, it is shown in the video that there is a tendency to change in shape during the journey on this front. The team found that this is largely due to an inertial effect, as the heavier central part moves less under a constant force. Crucially, it is this reversal that eventually causes a droplet, triggering a cascade of film breakdown events.
His work is in contrast to previous investigations that looked at individual films; The accumulation of liquid between RVPBs is only possible inside the foam, where the liquid can be supplied by the surrounding films and boundaries. The physical model they developed to describe dynamics was shown to give reliable predictions of frontal velocity and relevant time scales.
Finally, the team replaced the laboratory reagents with a household detergent and repeated the experiment, creating a more long-lasting foam. When a bubble bursts to the side, they found a similar accumulation of liquid in the center of the RVPB, although much lower than before.
The film’s increased elasticity also meant that two cracks were unlikely to form in the same film; This means that no droplets are formed, i.e., no mass bubble collapse: in light of the mechanism found above, this conclusively shows that less transport and fewer cracks within the RVPBs directly contribute to foam stability.
Such insights are important to guide the design of new foam materials with enhanced properties; The team hopes that their work can inspire state-of-the-art insulation materials, detergents, food products and cosmetics.
Researchers at Tokyo Metropolitan University are showing how liquid foam collapses by observing individual “events” with high-speed video microscopy. The cracks in the films lead to a liquid-liquid front that increases the original film boundary, changes its shape, and leaves a small drop that hits and breaks other films. His observations and physical models are providing important insights into how to make foam more or less resistant to collapse.
Foam collapse is a challenging problem. Prof. of Tokyo Metropolitan University. A team led by Ri Kurita is using liquid foam to sandwich between two thin, transparent plates, providing direct access to the full range of complex collapse. Until now, it was not known how the drops were formed and sometimes why they were not.
Researchers are making progress. When an initial crack is formed in a film, the film recurs and leaves a wobbling line of liquid where the original film was the boundary. This is called the Related Vertical Plateau Border (RVPB).
Wobbling causes the accumulation of liquid in the center of the RVPB. When another crack occurs in the rest of the film, a recurring line of liquid is created that sweeps the RVPB. This front has a tendency to reverse in shape as it travels due to an inertial effect.