MSGID: 1:317/3 645334f5   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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   
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   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.   
      
      
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   Related Multimedia:   
       * Bubble_images   
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   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   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230503121318.htm   
      
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