Have you ever been at a party holding a bottle of beer (other drinks are available) when someone walks over to you and bashes the top of your bottle with the bottom of theirs? This then causes your beer to uncontrollably overflow, leaving you no option but to attempt to swallow the froth as quick as it is produced. Whenever this happens you are left with two questions. Why did this happen and why did it work? The answer to the first can vary but is normally of the form “there is an idiot at this party”. The second however, is always a little more difficult to answer, but for no longer.
Image Credit: Matt King via Flickr ( License )
Thanks to physicists at the Carlos III University in Spain and Universite Pierre et Marie Curie in France we now know the answer. 1 The sudden impact at the top of the bottle causes a back and forth motion in the liquid, this causes bubbles to appear and then quickly collapse. The physicists discovered that there were two types of bubbles that form, which they called “mother” bubbles and “daughter” bubbles. Mother bubbles are formed after impact but it’s when they break up that the process of foamover begins. Mother bubbles break up in to smaller daughter bubbles which then expand rapidly. It is this rapid expansion that gives the bubbles buoyancy, and thus causing foamover.
The team’s work is not just useful for understanding a bottle of beer. It is thought that these ideas can be applied to engineering problems, such as the erosion of ship propellors, and to natural phenomena, such as the Lake Nyos disaster. 2
