Tokyo: Using Japan’s most powerful computer, researchers have explored how the physics of champagne bubbles may help address the world’s future energy needs. The team was able to simulate bubble nucleation process from the molecular level by harnessing the K computer at RIKEN – the most powerful system in Japan. In the bubble nucleation process, bubbles immediately form and then rapidly begin the process of “coarsening” in which larger bubbles grow at the expense of smaller ones. This fundamental phenomenon is known as “Ostwald ripening” and is familiar for its role in bubbly beverages. It is also seen in a wide range of scientific systems including spin systems, foams and metallic alloys.
On a much larger scale, “Ostwald ripening” can be observed in a power-generating turbine. Most power stations rely on boilers to convert water into steam but the phase transition involved is highly complex. During the phase transition, no one is exactly sure what is occurring inside the boiler – especially how bubbles form. So a team of researchers from the University of Tokyo, Kyusyu University and RIKEN in Japan set out to find an answer. At the heart of their work were molecular dynamics simulations. ”A huge number of molecules, however, are necessary to simulate bubbles – on the order of 10,000 are required to express a bubble,” said Hiroshi Watanabe, research associate at University of Tokyo’s institute for solid state physics. So the team needed at least this many to investigate hundreds of millions of molecules – a feat not possible on a single computer.
The team, in fact, wound up simulating a whopping 700 million particles, following their collective motions through a million time steps – a feat they accomplished by performing massively parallel simulations using 4,000 processors on the K computer. This was, to the best of their knowledge, the first simulation to investigate multi-bubble nuclei without relying on any artificial conditions. As far as implications of the team’s work, an enhanced understanding of the behavior of bubbles is very important for the field of engineering because it may enable the design of more efficient power stations or propellers. The research appeared in the Journal of Chemical Physics.