Unraveling turbulence

Turbulence is everywhere -- it rattles our airplanes and makes tiny whirlpools in our bathtubs -- but it's one of the least understood phenomena in physics.

Turbulence occurs when an ordered fluid flow breaks into small vortices, and these whirlpools interact with each other and break into even smaller vortices, which also interact with each other and so on, becoming the chaotic maelstrom of disorder that makes whitewater rafting fun. The mechanics of that descent into chaos have puzzled scientists for centuries.

When they don't understand something, physicists have a go-to solution: smash it together. Want to understand the fundamental building blocks of the universe? Smash particles together. Want to unravel the underlying mechanics of turbulence? Smash vortices together.

National Science Foundation-funded researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences may have identified a fundamental mechanism of how turbulence develops by smashing vortex rings into each other head-on, recording the results with ultra-high-resolution cameras, and reconstructing the collision dynamics using a 3D visualization program.

Coupled with the analysis of numerical simulations performed by collaborators at the University of Houston and ENS de Lyon, the researchers have gained new insights into how fluid systems transform from order to disorder.

The results are described in Science Advances.

"Our ability to predict the weather, understand why a Boeing 747 flies even with turbulent currents in its wake, and determine global flows in the ocean depends on how well we model turbulence," said Shmuel Rubinstein, corresponding author of the paper. "But our understanding of turbulence still lacks a description that explains how energy cascades to smaller and smaller scales until it is eventually dissipated. This research opens the door to just that kind of understanding."

The results affect our daily lives, whether in the air or on the ground.