Numerical simulations of bubbly flows for the pint and anti-pint.. The curves show the streamlines for the bubbles, the colour shows the void fraction f. The snapshots displayed correspond to t = 4 s.
Yesterday was St Patrick’s day, celebrated world wide, probably with a pint of Guinness. Perhaps while sipping down a pint you may have wondered why do bubbles in Guinness sink? Here is one-of-a kind paper that discusses just this! They concluded that the flow in a glass of stout depends on the shape of the glass. If it narrows downwards (as the traditional stout glass, the pint, does), the flow is directed downwards near the wall and upwards in the interior and sinking bubbles will be observed. If the container widens downwards, the flow is opposite to that described above and only rising bubbles will be seen (
http://arxiv.org/abs/1205.5233).
Read it all here:
http://arxiv.org/pdf/1205.5233v1
