Max Koch, a researcher at the German University of Göttingen and a connoisseur of homebrew, has experimentally worked on a scientific problem that has long been of interest to mankind.
The scientist used a high-speed camera to record what happens when you open a bottle of homebrew with a twist-off cap. Thereafter, he and his colleagues decided to expand the home experiment and investigate the acoustic and physical aspects of the phenomenon. The study was published in Physics of Fluids.
The team found that the sound of a pressurized bottle opening — is not a single shock wave, but a very fast «ah» type sound. High-speed video recordings captured condensation inside the bottle’s mouth in a liquid that vibrated up and down in a standing wave. These recordings, along with high-fidelity audio recordings and fluid dynamics simulations, confirmed that this wave was the source of the «ah» sound.
«The frequency of the sound is much lower than the resonance when you blow on a full bottle like a whistle. This is caused by the sudden expansion of the carbon dioxide and air mixture in the bottle, as well as the strong cooling effect down to around -50 °C, which reduces the speed of sound. The decibels that are emitted are high — at the throat of the bottle, the sound is as loud or even louder than an airplane turbine within a 1-meter radius, but it doesn’t last long,— Koch explains.
When the bottle is opened, dissolved carbon dioxide is released inside, causing the liquid level to rise. The movement of the bottle also causes the liquid to splash. In addition, the momentum transfer of the cap, which hits the glass with the edge after bouncing off, can also trigger fountaining due to increased bubble formation.
«It was a challenge to explain the low frequency of the sound «ah» during the discovery, and to find a simple model to explain the values. One thing we couldn’t solve is that our numerical simulations showed an initial strong peak in acoustic emission before the short resonance «ah», but this peak was absent in the experiment,” says Koch.
The researcher jokes that another big challenge was maintaining the accuracy of the experiment while consuming the homemade drink. The author of the news story feels that the experiment needs to be tested immediately on Friday night.
Source: SciTechDaily
