ZME Science
  • News
  • Environment
    • Animals
    • Climate
    • Renewable Energy
    • Eco tips
    • Environmental Issues
    • Green Living
  • Health
    • Alternative Medicine
    • Anatomy
    • Diseases
    • Genetics
    • Mind & Brain
    • Nutrition
  • FutureNEW
  • Space
  • Feature
    • Feature Post
    • Art
    • Great Pics
    • Design
    • Fossil Friday
    • AstroPicture
    • GeoPicture
    • Did you know?
    • Offbeat
  • More
    • About
    • The Team
    • Advertise
    • Contribute
    • Our stance on climate change
    • Privacy Policy
    • Contact
No Result
View All Result
ZME Science

No Result
View All Result
ZME Science
No Result
View All Result
HomeOtherOffbeat

Why the bubbles from Guinness go down, not up

The beer bubbles exhibit an unusual phenomenon, which researchers felt warrants a closer look.

Mihai Andrei byMihai Andrei
May 6, 2019
inOffbeat, Physics
Share on FacebookShare on TwitterSubmit to Reddit

This article is, unfortunately, not sponsored by Guinness — but we’re open for discussion.

Image via Pixabay.

Beer is one of the most popular drinks in the world, and physicists take their beer very seriously. In a new study, a team of Japanese researchers analyzed an unusual phenomenon related to one of the most famous and recognizable beers in the world: Guinness.

Guinness is an Irish dark stout. It’s known for its remarkable taste and creamy texture, but researchers were interested in one thing which might escape most patrons of a pub: its bubbles. Imagine pouring yourself a beer, and try to visualize the bubbles. They go up, right? According to Archimedes’ principle, bubbles in liquid generally rise because of the gas-liquid density difference. Yet in a pint of Guinness, bubbles also go down.

ADVERTISEMENT

Several studies have addressed this unusual issue, but overall, the process is still somewhat of a mystery — in part due to the beer’s black color, which obstructs all observations. A previous study claimed that the bubbles’ unusual behavior is owed to the particular shape of the Guinness glass. Now, a team led by Tomoaki Watamura from the University of Osaka, reports that that’s not really the case. Instead, there’s a much more physical reason for how the bubbles behave.

“We performed experiments on the bubble distribution in Guinness poured in an inclined container, and observed how the texture forms,” the study reads. “We also report the texture-formation in controllable experiments using particle suspensions with precisely specified diameters and volume-concentrations.”

The team combined direct observations with laser-induced-fluorescence and computer models to create a detailed profile of the liquid phase velocity. They also used three different types of containers: a pint glass, an inclined rectangular container, and a trapezium-shaped container. They also used a customized setting for lighting and imaging, as well as a Guinness-like water suspension for better visibility.

Image credits: Watamura et al.

They found that, for starters, the bubbles in Guinness are much smaller than those in most beers or champagnes — about 10 times smaller. The bubbles-going-down effect does not take place in any fluid with large bubbles — but this doesn’t fully explain the phenomenon. Instead, researchers say, Guinness behaves much like a water film sliding downhill on a rainy day.

When the beer is poured into a typical pint glass (which is wider towards the top), the rising motion of the bubbles creates a film of bubble-free liquid above the inclined wall. This dense film falls, causing the lighter bubble-rich bulk to rise — something which is known as the Boycott effect. Accordingly, this engages the bubbles at the edge of the container, creating a cascade of descending bubbles entrained into the downward flow in Guinness, which is seemingly paradoxical in light of Archimedes’ principle.

ADVERTISEMENT
Textures in Guinness and a particle suspension. Image credits: Watamura et al.

The key parameter here is the ratio between the inertia force and the gravity force. This ratio is an indicator for something called the onset of the roll-wave in a liquid-film. Remember when we said Guinness was behaving like rain sliding down on a hill? It’s exactly the same phenomenon: the same ratio (between inertia and gravity) directs the formation of water film sliding down. The cascading waves collide and coalesce with their neighbors, creating a particular structure and a downstream motion.

Essentially, the bubble cascade in Guinness beer is caused by gravity current instability.

“The hydrodynamic condition for the texture-formation is analogous to the critical point of the roll-wave instability in a fluid film, which can be commonly observed in water films sliding downhill on a rainy day. Here, we identify the critical condition for the texture-formation and conclude that the roll-wave instability of the gravity current is responsible for the texture-formation in a glass of Guinness beer,” the researchers conclude.

The study has been published in Scientific Reports.

 

ShareTweetShare

How much money are you losing by not going solar? Use our savings calculator for rooftop solar.

Mihai Andrei

Mihai Andrei

Andrei's background is in geophysics, and he's been fascinated by it ever since he was a child. Feeling that there is a gap between scientists and the general audience, he started ZME Science -- and the results are what you see today.

ADVERTISEMENT

EDITOR'S PICKS

Leaf blowers are not only annoying but also bad for you (and the environment)
Environment

Leaf blowers are not only annoying but also bad for you (and the environment)

by Alexandru Micu
November 15, 2019 - Updated on November 17, 2019

It comes down to the inefficient engines they use.

Read more
What are greenhouse gases and why we need to worry about them? A simple explainer

What are greenhouse gases and why we need to worry about them? A simple explainer

November 15, 2019
The difference between programming and coding with Leslie Lamport

The difference between programming and coding with Leslie Lamport

November 15, 2019
Why ketamine is so good against depression

Why ketamine is so good against depression

November 8, 2019
pixabay-brain-fog

What is brain fog: the mental fatigue that ruins your mood

October 25, 2019
ADVERTISEMENT
  • News
  • Environment
  • Health
  • Future
  • Space
  • Feature
  • More

© 2007-2019 ZME Science - Not exactly rocket science. All Rights Reserved.

No Result
View All Result
  • News
  • Environment
    • Animals
    • Climate
    • Renewable Energy
    • Eco tips
    • Environmental Issues
    • Green Living
  • Health
    • Alternative Medicine
    • Anatomy
    • Diseases
    • Genetics
    • Mind & Brain
    • Nutrition
  • Future
  • Space
  • Feature
    • Feature Post
    • Art
    • Great Pics
    • Design
    • Fossil Friday
    • AstroPicture
    • GeoPicture
    • Did you know?
    • Offbeat
  • More
    • About
    • The Team
    • Advertise
    • Contribute
    • Our stance on climate change
    • Privacy Policy
    • Contact

© 2007-2019 ZME Science - Not exactly rocket science. All Rights Reserved.

Do you love science?

Join 50,000+ subscribers and get our FREE e-book on pseudoscience. 
SUBSCRIBE
close-link