New Research


2018/01/01

Bubbles and physics in a glass of drink

Professor Sugiyama Research Group

Bubbles in sparkling drinks such as carbonated water and beer carry sensory flavour and mouthfeel. Upon watching a glass of drinks, we observe multi-scale physical phenomena involved therein. In a soda poured, bubbles of carbon dioxide gas are produced from tiny "scratches" at the glass wall. The bubbles rapidly grow up typically to 500 μm in diameter, and rise to the surface once detached from the wall because of the buoyancy.

Changing the dissolved gas species reveals a drastically different behavior of growing and rising bubbles released from a super-saturated solution. The left panel in figure shows a snapshot of a nitrogen-dissolved drink in a glass. Even fully grown, the bubbles are typically as small as 50 μm in diameter (being around one-tenth of that in carbonated drinks), and rise very slowly. Thanks to a great number of tiny bubbles dispersed for a long period, we can enjoy the creamy taste, and looking at a texture of cascading bubble swarm (see the second panel from left in figure). Focusing on the fascinating texture, we have investigated the fluid mechanics underlying its formation, and found a mechanism that the texture appearance is triggered by a buoyancy-driven instability different from that for a cell pattern formation in a bowl of "miso-soup".

The mechanism why and how such a tiny bubble forms in the nitrogen-dissolved drink has not been fully understood, even though attributed to the amount and species of the dissolved gas. We may raise a possible cause also in dynamics, corresponding to the "suppression of bubble-bubble coalescence" owing to the contamination of surfactants (suspended in the solution) onto the gas-liquid interface (as illustrated in the right panel). We are conducting experimental and numerical studies to afford insight into the mechanical law behind sparkling drinks.

Bubbly flows are observed in a wide range of industrial applications (e.g., heat exchangers in electric power plants, and aeration chambers in water purification facilities) as well as in sparkling drinks. Utilizing the fundamental knowledge and technique acquired through the above-mentioned studies, we are also tackling the practical research problems.

Sugiyama Lab. HP

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