You probably don’t think of a wedding (or birthday, or any celebration), as the natural place to carry out a physics experiment, but they have a lot more in common with rocket science than you might think.
That’s according to a recent paper, accepted last month for publication in the American Institute of Physics journal Physics of Fluids. Using Computational Fluid Dynamics (CFD) simulations, researchers have revealed a dramatic sequence of supersonic shock waves forming, evolving, and dissipating at supersonic speeds, all within the first millisecond after a champagne bottle is opened.
“Behind the iconic ‘pop!’ accompanying the uncorking of a champagne bottle hides a gas flow of surprising complexity,” write the authors. “Its modeling is made delicate by its supersonic nature, its interaction with the cork stopper, the eminently unsteady character of the flow escaping from the bottle, and the continuous change of the geometry of the computational flow domain due to the displacement of the cork.”
So what exactly is going on when we pop open that cork? To us, with our surprisingly low FPS vision, it’s a simple process of pulling out the stopper and aiming the bubbles away from people's faces – but under super-high-speed imaging, we start to see much more explosive detail.
At first, the gas mixture inside the bottle is prevented from escaping by the cork – but as we pull it free, a crown-shaped shock wave of gas shoots out around the stopper at speeds of nearly 1,500 kilometers per hour – that’s quite a bit faster than the speed of sound. The waves combine together to form a phenomenon known as shock diamonds – an appropriately rich name in this instance, considering their provenance, but something more typically seen in the exhaust plumes of rocket launches.
Then, about two-thirds of a millisecond later, a completely different type of shock wave is formed. At this point, the cork has moved far enough out of the bottle to allow for a cylindrical, rather than radial, gas flow – but not yet far enough to actually get out of the way of the gas. And when this happens, we get something called a detached shock wave, or bow shock – the kind of shock waves that are more often associated with bullets and cosmic phenomena than with celebratory drinks.
“Our paper unravels the unexpected and beautiful flow patterns that are hidden right under our nose each time a bottle of bubbly is uncorked,” said co-author Gérard Liger-Belair. “Who could have imagined the complex and aesthetic phenomena hidden behind such a common situation experienced by any one of us?”
The paper isn’t the first to explore the supersonic physics behind the opening of a champagne bottle – Liger-Blair and his colleagues previously showed supersonic CO2 freezing jets being expelled from the bottle, causing dry ice to form and light to be scattered in the atmosphere. It likely won’t be the last, either, as the team have plans to explore the impact of things like the temperature or size of the bottle on the process of uncorking champagne. And despite what you may be thinking, it’s not just an excuse for a posh drink either – this research has very real applications, in areas as diverse as ballistics, electronics manufacturing, wind turbines, and even ocean exploration.
"We wanted to better characterize the unexpected phenomenon of a supersonic flow that takes place during champagne bottle uncorking," said co-author Robert Georges. "We hope our simulations will offer some interesting leads to researchers, and they might consider the typical bottle of champagne as a mini-laboratory."