Falling stout bubbles explained

[zippy]

Irish mathematicians may have solved the mystery of why bubbles in stout beers such as Guinness sink: it may simply be down to the glass.

Simulations suggest an upward flow at the glass's centre and a downward flow at its edges in which the liquid carried the bubbles down with it.

http://www.bbc.co.uk/news/science-environment-18247680