Mystery of texture of Guinness beer: Inclination angle of a pint glass is key to solution

phys.org | 5/29/2012 | Staff
samtetley (Posted by) Level 3
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A team of researchers from Osaka University and Kirin Holdings Company, Limited demonstrated that the texture formation in a pint glass of Guinness beer is induced by flow of a bubble-free fluid film flowing down along the wall of the glass, a world first. This phenomenon is found to be analogous to roll waves commonly observed in water sliding downhill on a rainy day. Their research results were published in Scientific Reports.

Guinness beer, a dark stout beer, is pressurized with nitrogen gas. When it is poured into a pint glass, small-diameter bubbles (only 1/10 the size of those in carbonated drinks such as soda and carbonated water) disperse throughout the entire glass and the texture motion of the bubble swarm moves downward.

Models - Wave - Swarm - Forms - Guinness

Although some models have been proposed to explain how the downward wave of a bubble swarm forms in Guinness beer, the mechanism underlying the texture formation was an open problem.

Because the opaque and dark-colored Guinness beer obstructs physical observation in a glass, and computation using supercomputers is necessary to conduct numerical simulation of flows including a vast number of small bubbles in the beer, the team of researchers led by Tomoaki Watamura produced transparent "pseudo-Guinness fluid" by using light particles and tap water. They filmed the movement of liquid with a high-speed video camera,...
(Excerpt) Read more at: phys.org
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