Physics Involved in Foaming of Beer Bottles Explained by Researchers

An annoying prank that everyone has experienced or indulged in is the tapping of beer to watch the beer suds foaming up and spreading all over.  Have you ever wondered at the reason why?

 A team of scientists has put an end to our curiosity by giving an insight into the physics behind foaming beer bottles.

In a new finding, researchers at Carlos III University in Madrid, Spain, in collaboration with researchers at the Universite Pierre et Marie Curie, Institut Jean le Rond d'Alembert, France, have explained the science behind beer tapping by exploring the phenomenon of cavitation- used in engineering concerns such as erosion of ship propellers.

According to Javier Rodriguez-Rodriguez, the lead researcher from Carlos III University, 'cavitation' is the real mechanism behind bubble formations after an impact - as seen in beers.

During an impact against a bottle's mouth, the back and forth movement of compression and expansion waves trigger the formation of bubbles that quickly collapse. On investigating the beer bottle-fluid interactions, the researchers showed that due to cavitations the bigger bubbles (mother bubbles) form clouds of tiny carbonic gas (daughter bubbles) that later become large and expand at a faster rate than the bigger bubbles from which they divide. It is the extremely quick expansion of the daughter bubbles that actually gives the foam buoyancy.

"Buoyancy leads to the formation of plumes full of bubbles, whose shape resembles very much the mushrooms seen after powerful explosions," Rodriguez-Rodriguez said in a statement. "And here is what really makes the formation of foam so explosive: the larger the bubbles get, the faster they rise, and the other way around" - because fast-moving bubbles draw additional carbonic gas.

This is the first quantitative analysis of beer bottle foam.

"We wanted to explain the extremely high efficiency of the degasification process that occurs in a beer bottle within the first few seconds after the impact," Rodriguez said.

The researchers believe that this phenomenon can be applied to understand some of the serious natural phenomena such as sudden release of dissolved carbon dioxide in the Lake Nyos disaster.

The finding was presented at the annual meeting of the American Physical Society (APS) Division of Fluid Dynamics.