Why do Champagne bubbles rise the way they do? Scientists' new discovery
is worthy of a toast
Surfactants give the celebratory drink its stable and signature straight
rise of bubbles

Date:
May 3, 2023
Source:
Brown University
Summary:
ere are some scientific findings worthy of a toast: Researchers
have explained why bubbles in Champagne fizz up in a straight line
while bubbles in other carbonated drinks, like beer or soda, don't.


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FULL STORY ==========================================================================
Here are some scientific findings worthy of a toast: Researchers from
Brown University and the University of Toulouse in France have explained
why bubbles in Champagne fizz up in a straight line while bubbles in
other carbonated drinks, like beer or soda, don't.

The findings, described in a new Physical Review Fluidsstudy, are based
on a series of numerical and physical experiments, including, of course, pouring out glasses of Champagne, beer, sparkling water and sparkling
wine. The results not only explain what gives Champagne its line of
bubbles but may hold important implications for understanding bubbly
flows in the field of fluid mechanics.

"This is the type of research that I've been working out for years," said
Brown engineering professor Roberto Zenit, who was one of the paper's
authors. "Most people have never seen an ocean seep or an aeration tank
but most of them have had a soda, a beer or a glass of Champagne. By
talking about Champagne and beer, our master plan is to make people
understand that fluid mechanics is important in their daily lives."
The team's goal was to investigate the stability of bubble chains in
carbonated drinks. Part of the signature experience of enjoying these
beverages is the tiny or large bubbles that form when the drink is poured, creating a visible chain of bubbles and fizz. Depending on the drink
and its ingredients, the fluid mechanics involved are all different.

When it comes to Champagne and sparkling wine, for instance, the gas
bubbles that continuously appear rise rapidly to the top in a single-file
line and keep doing so for some time. This is known as a stable bubble
chain. With other carbonated drinks, like beer, many bubbles veer off
to the side, making it look like multiple bubbles are coming up at
once. This means the bubble chain isn't stable.

The researchers set out to explore the mechanics of what makes bubble
chains stable and if they could recreate them, making unstable chains
as stable as they are in Champagne or prosecco.

The results of their experiments indicate that the stable bubble chains
in Champagne and other sparkling wines occur due to ingredients that
act as soap- like compounds called surfactants. These surfactant-like
molecules help reduce the tensions between the liquid and the gas bubbles, making for a smooth rise to the top.

"The theory is that in Champagne these contaminants that act as
surfactants are the good stuff," said Zenit, senior author on the
paper. "These protein molecules that give flavor and uniqueness to
the liquid are what makes the bubbles chains they produce stable."
The experiments also showed the stability of bubbles is impacted by
the size of the bubbles themselves. They found that the chains with
large bubbles have a wake similar to that of bubbles with contaminants,
leading to a smooth rise and stable chains.

In beverages, however, bubbles are always small. It makes surfactants
the key ingredient to producing straight and stable chains. Beer,
for example, also contains surfactant-like molecules but, depending on
the type of beer, the bubbles can rise in straight chains or not. In
contrast, bubbles in carbonated water are always unstable since there
are no contaminants helping the bubbles move smoothly through the wake
flows left behind by the other bubbles in the chain.

"This wake, this velocity disturbance, causes the bubbles to be knocked
out," Zenit said. "Instead of having one line, the bubbles end up
going up in more of a cone." The results in the new study go well
beyond understanding the science that goes into celebratory toasts,
the researchers said. The findings provide a general framework in fluid mechanics for understanding the formation of clusters in bubbly flows,
which have economic and societal value.

Technologies that use bubble-induced mixing, like aeration tanks at
water treatment facilities, for instance, would benefit greatly from researchers having a clearer understanding of how bubbles cluster, their origins and how to predict their appearance. In nature, understanding
these flows may help better explain ocean seeps in which methane and
carbon dioxide emerges from the bottom of the ocean.

The experiments the research team ran were relatively straightforward
-- and some could even be run in any local pub. To observe the bubble
chains, the researchers poured glasses of carbonated beverages including Pellegrino sparkling water, Tecate beer, Charles de Cazanove champagne
and a Spanish-style brut.

To study the bubble chains and what goes into making them stable, they
filled a small rectangular plexiglass container with liquid and inserted
a needle at the bottom so they could pump in gas to create different
kinds of bubble chains.

The researchers then gradually added surfactants or increased bubble
size. They found that when they made the bubbles larger, they could make unstable bubble chains become stable, even without surfactants. When
they kept a fixed bubble size and only added surfactants, they found
they could also go from unstable chains to stable ones.

The two experiments indicate that there are two distinct possibilities to stabilize a bubble chain: adding surfactants and making bubbles bigger,
the researchers explain in the paper.

The researchers performed numerical simulations on a computer to
explain some of the questions they couldn't explain through the physical experiments, such as calculating how much of the surfactants go into
the gas bubbles, the weight of the bubbles and their precise velocity.

They plan to keep looking into the mechanics of stable bubble chains
in an effort to apply them to different aspects of fluid mechanics,
especially in bubbly flows.

"We're interested in how these bubbles move and their relationship to industrial applications and in nature," Zenit said.

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========================================================================== Story Source: Materials provided by Brown_University. Note: Content may
be edited for style and length.


========================================================================== Related Multimedia:
* Bubble_images ========================================================================== Journal Reference:
1. Omer Atasi, Mithun Ravisankar, Dominique Legendre, Roberto Zenit.

Presence of surfactants controls the stability of bubble chains
in carbonated drinks. Physical Review Fluids, 2023; 8 (5) DOI:
10.1103/ PhysRevFluids.8.053601 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230503121318.htm

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