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As you raise a glass of Champagne on New Year's Eve, include a toast to the physics behind the fizz: The scientific mysteries sealed up in all those bubbles could someday lead to more efficient energy sources.
The latest in bubble lore came out just this month in the Journal of Chemical Physics. Japanese researchers used computer simulations to study the molecular mechanics behind the formation of bubbles, particularly how larger bubbles grow at the expense of smaller ones.
The process, called "Ostwald ripening," can be seen whenever you crack open a bottle of sparkling wine or soda and pour it into a glass. But the researchers at the University of Tokyo, Kyushu University and the RIKEN computer lab weren't interested in how beverages go pop. Instead, they wanted to find out how to make steam-powered turbines more efficient.
Like the Champagne in a glass, the bubbles of water vapor that are created in a turbine's water tank also go through Ostwald ripening. In a steam turbine, the way those bubbles grow can have an big impact on how efficiently power is converted from a boiler's blast to a dynamo's drive.
Molecular model mystery
Physicists have developed a well-supported theoretical model for the formation of water droplets in condensation, but that model doesn't work when it comes to predicting how bubbles form in a superheated liquid. The Japanese researchers' computer simulation was aimed at analyzing how bubble formation, or cavitation, should work at a molecular level. If they found some previously unknown twist in the process, that could resolve the mystery.
"In the past, while many researchers wanted to explore bubble nuclei from the molecular level, it was difficult due to a lack of computational power," Hiroshi Watanabe, a research associate at the University of Tokyo's Institute of Solid State Physics, said in a news release from the American Institute of Physics. "But now, several petascale computers — systems capable of reaching performance in excess of one quadrillion point operations per second — are available around the world, which enable huge simulations."
RIKEN's 4,000-processor K computer simulated the interactions of 700 million molecules through a million time steps — and found that the simulated bubble formation process matched the theoretical model. "We were expecting the classical theory to fail to describe the bubble systems, but were surprised to find that it held up," Watanabe said.
As a result, the mystery remains. Now Watanabe and his colleagues are moving on from simulating bubble cavitation to simulating how boiling water gives rise to bubbles.
"Bubbles appear when liquid is heated as 'boiling,' or as 'cavitation' when the pressure of the liquid decreases," Watanabe said in the AIP news release. "Simulating boiling is more difficult than cavitation at the molecular level, but it will provide us with new knowledge that can be directly applied to designing a more efficient dynamo."
The science of sipping Champagne
But what about a more efficient Champagne toast? Thankfully, other researchers have solved that mystery.
Scientists from the Champagne region of France (where else?) say the key to enjoying sparkling wine is to maximize the bubble-bursting effect on your palate. That's what releases the mouth-pleasing fizz of carbon dioxide — as well as the volatile organic compounds, or VOCs, that give the wine its flavor.
Here are the top five tips from researchers at the University of Reims:
The colder, the better: Warm Champagne loses its CO2 more quickly when it's opened (sometimes, in a big rush of foam) as well as when it's poured.
Flutes, not coupes: The tall, narrow-rimmed glasses known as flutes preserve the CO2 better than the wide-rimmed, bowl-shaped glasses known as coupes. That's because the narrow glasses present less surface area per unit of volume, reducing CO2 loss into the air.
Pour it down the side: Whichever glass you use, pouring the wine down the angled side of the glass will preserve more of the CO2 than splashing it into the middle of the glass. If you want to make a splash, that's fine — it's just that once the foam settles, the wine will be left with less of the bubbly stuff.
Use a smooth glass: Studies show that sparkling wine releases its CO2 more quickly if it's poured into a scratched glass. The scratches — as well as fabric fibers that may have been left in the glass after vigorous towel drying — promote the rapid nucleation of CO2 bubbles. Some folks prefer to use etched glasses, because the microscratches create bubbles in pretty patterns. But if you want those bubbles to stick around until they're released into your nose, use unmarked glasses — and air-dry them after they're washed.
In addition to Watanabe, the authors of the paper published by the Journal of Chemical Physics, "Ostwald Ripening in Multiple-Bubble Nuclei," include Masaru Suzuki, Hajime Inaoka and Nobuyasu Ito.