Turbulent times in the aquarium

While turbulence is everywhere – from planes to white water rafting and whirlpools in the bathtub – it’s one of the least understood phenomena in physics.

The image above is of vortex cannons firing in a 75-gallon aquarium to produce vortices, in an attempt to identify a fundamental mechanism by which they spiral into chaos and create turbulence.

Although physicists have been using vortex colliders to understand turbulences since the 1990s, until now they haven’t been able to slow the experiments down enough to capture the moment a collision descends into chaos.

A team of researchers from the US and France dyed each vortex a different colour so they could observe how they interact when they violently collide head-on using a high-speed camera that could snap hundreds of thousands of images per second, publishing their findings in the journal Science Advances. 

They found that it takes less than a second for the rings to disappear into a puff of dye after the collision. But within that time, a lot of physics happens.

“The violent interaction between two counter-rotating vortices leads to the rapid emergence of a turbulent cascade,” the researchers write, “resulting in a flow with an energy spectrum that—for an ethereal moment—obeys Kolmogorov scaling.”

Lead author Ryan McKeown says the cascading effect “is very exciting because it could point to a universal mechanism for how these interactions work, independent of scale.”