lead paper in the American Journal of Physics regards a subject that is dear to most grad students hearts, beer. A team of scientists Limerick, Ireland report on research they did to determine why the bubbles near the wall of a pint glass of Guinness flow down instead of up. The preprint of the article can be found on arXiv. The article inoduces fluid mechanics of the physics of the 'bubbly flow'. In addition to the bubbly flow, the article introduces the 'anti-pint' (picture 1). One wonders if the phrase was coined while the research team performed the experimental portion of their work, measuring the settling time of a Guinness Stout.
If you have a fear of fluid mechanics like I did until today, then this article is an excellent gentle introduction to the subject. In terms of their relation to your Guinness, the article introduces the Reynolds number, the ratio of inertial to viscous forces in a fluid flow, and the Bond number, a parameter that defines the weight (pun intended), of gravity on the shape of a bubble, and Stokes Formula to determine the drag force on bubbles in the beer.
The article surmises that the downward flow of bubbles is due to the Boycott Effect discovered by Dr. Boycott in 1920. If you've ever wondered why the doctor in medical dramas holds the test tube of blood at an angle, there's actually a reason. The tilt influences the flow of sediment, (blood corpuscles in this case), and the settling time is reduced. An example of this is shown in the video of Guinness in a tube below.
1. The article in question on arXiv:
2. Reynolds Number:
3. Bond Number:
4. About the research team:
5. Boycott Effect:
6. Stokes' Formula7. The tilted Guiness video:
8. The AJP article
On waves in Guiness: