Today, one week after New Year’s, champagne bottles are still lining many recycling bins as a final reminder of our celebrations that brought in 2015. But for some physicists, champagne (or more specifically, the science behind its bubbly nature) is especially meaningful this year, as it helped to confirm a more than 50-year-old theory of fluid dynamics.
“Bubbles are very common in our everyday life,” says Gérard Liger-Belair, a physicist at the University of Reims in France. “They play a crucial role in many natural as well as industrial processes—in physics, chemical and mechanical engineering, oceanography, geophysics, technology and even medicine. Nevertheless, their behavior is often surprising and, in many cases, still not fully understood.”
The main mystery are looking to solve centers around how quickly differently sized bubbles are able to form in a liquid, which in turn could help engineers to design more efficient boilers for steam-powered reactors.
The basis for the research began with the work of a 19th-century German chemist named Wilhelm Ostwald, who observed that smaller particles in a solution will give way to larger ones because they are more energetically stable.
“After many bubbles appear at the moment of uncorking a champagne [bottle], the population of bubbles starts to decrease,” says study co-author Hiroshi Watanabe, a physicist at the University of Tokyo. “Larger bubbles become larger by eating smaller bubbles, and finally only one bubble will survive.”
Similarly, this principle explains why refrozen ice cream loses so much of its ori
ginal, smooth texture – when the mixture melts and solidifies it naturally favors the larger ice crystals that we associate with freezer burn.
But to build off Ostwald’s work researchers have stepped out of the kitchen and into the power plant, where bubbles cause problems by decreasing heat exchange and eroding metal surfaces. There, Watanabe’s research could one day help to engineer better equipment, but the formation of bubbles is especially difficult to study and understand due to the incredible number of bubbles present.
To take that first step, Watanabe and his colleagues from Kyusyu University and RIKEN labs turned to Japan’s top-ranking K supercomputer to simulate millions of virtual molecules and study how quickly they formed bubbles within a closed environment.
One million node hours and 700 million simulated molecules later, the scientists found were able to observe how bubbles evolve en masse. A scaled-down version of their simulation is shown below, showing how many smaller bubbles eventually consolidate into one:
For Watanabe and his team, the model has helped confirm that bubble behavior is modeled by a mathematical framework from the 1960’s called Lifshitz-Slyozov-Wagner (LSW) theory.
The theory explains that at the moment in which bubbles are first allowed to form, (such as upon popping a champagne cork,) the rate of bubble formation is limited by the speed at which the liquid molecules can become gas, but as more gas forms and the bubble grows larger, the speed at which more liquid can reach the bubble’s surface takes over as the governing force.
Right now, Watanabe says that the study isn’t ready to help engineer better boilers, “…but this is the first step to understand how bubbles appear and how bubbles interact with each other during the bubble formation from the molecular level.”
The results appear in December 2014’s issue of the Journal of Chemical Physics.