The wind blows steadily, but suddenly a gust hits, and leaves swirl up in a vortex. Inside such a gust, the air speed changes not smoothly but in jumps — sometimes sharply forward, sometimes sideways. These rare and strong bursts are called intermittency, and they are the main mystery of turbulence.
For a long time, scientists described such jumps by measuring velocity only along the flow, as if watching a river from the bank and following a twig floating downstream. But water also has transverse motions: eddies, rises, and falls. It turns out that these transverse bursts are stronger and occur more often than simple models would predict.
The authors of the new work linked both directions into a single framework. They showed that for longitudinal velocity jumps, everything is resolved the old way — from measurements along the flow. But for transverse jumps, you need both longitudinal and transverse data together. It's like predicting ripples on water requires knowing not only the current speed but also how the water swirls near the banks.
Now scientists have a tool that sees turbulence as a whole — both along and across. This means we can more accurately calculate air mixing in the atmosphere, water movement in the ocean, and even flows inside engines.
A Reynolds number of 1300 in this work is like stirring milk into a cup of coffee so fast that the vortices break into thousands of tiny whirlpools, and you need to account for all of them at once.