Uncorking a cold bottle of champagne releases carbon dioxide gas in a series of shock waves, many of which are faster than the speed of sound.
Champagne uncorking may seem simple, but high-speed images have previously shown that high-pressured, cold carbon dioxide gas escapes in a more complicated series of steps than expected. 鈥淐hampagne should be considered a 鈥榤ini鈥� laboratory for the physics of fluids,鈥� says at the University of Rennes 1 in France.
Georges and his colleagues simulated uncorking a champagne bottle on a computer to determine the speed and shape of shock waves formed by escaping carbon dioxide. Their simulation consisted of a bottle, a jet of gas escaping it and the bottle鈥檚 cork, which flies out and keeps moving ahead of the gas. The computer solved a set of well-known yet notoriously difficult equations that describe how fluids flow when cold, under pressure and against walls and obstacles.
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The team found that immediately after the cork pops, the high-pressured gas behind it doesn鈥檛 have enough space to shoot straight out, so it forms a fast, radially expanding shock wave resembling a crown.
Two-thirds of a millisecond later, the cork moves away from the bottleneck enough for the gas to form a cylindrical supersonic jet. The gas keeps coming out of the bottle and running head-on into the cork, which slows it down and leads to the formation of a curved wave behind it.
After a whole millisecond, enough gas has left the bottle for the pressure inside to significantly drop, so the carbon dioxide flow slows down. The champagne then settles into something you can pour into glasses rather than a small explosion.
The fastest jets formed at the very beginning of the uncorking and reached speeds of nearly 1500 kilometres per hour, which is about 20 per cent faster than the speed of sound.
Pinpointing the minute details of champagne uncorking may help researchers better understand technology that involves supersonic jets. One example is in rocket design where supersonic nozzles eject gases to propel space vehicles. Another may be supersonic underwater craft like submarines.
Georges and his colleagues plan to add more detail into their simulations in the future by modelling bottles with different temperatures, shapes and sizes.
Physics of Fluids