UCSD - University of California - San Diego

04/24/2026 | Press release | Distributed by Public on 04/24/2026 09:08

How Does Turbulence Spread

Published Date

April 24, 2026

Article Content

A research team, including University of California San Diego Chancellor's Distinguished Professor of Physics Nigel Goldenfeld, created an experiment in which vortex rings were fired into the center of a water tank from all corners. This created what is known as "the Blob" - a perfect, stationary ball of turbulence that existed on its own at the center of the tank, free from boundaries. Researchers then watched as it spread and decayed.

They discovered they could explain the results using a modified version of a simple turbulence model that resulted in a nonlinear diffusion equation - different from the usual diffusion that governs heat flow, for example. The main finding was a detailed observation of a sharp front separating the turbulence from the non-turbulent fluid, in agreement with theory and earlier crude observations in superfluid helium by Goldenfeld and late physicist Russell Donnelly. However, the team's data were not consistent with various theoretical ideas about turbulence decay, thus apparently ruling out those theories.

The study was published February 12, 2026 in the Proceedings of the National Academy of Sciences (PNAS) and was conducted by Nigel Goldenfeld (UC San Diego), Takumi Matsuzawa, Minhui Zhu and William T. M. Irvine. Their research was funded by the U.S. Army Research Office (W911NF-17-S-0002, W911NF-18-1-0046, and W911NF-20-1-0117), the Simons Foundation (662985) and Schmidt Science Fellows.

Read the study in PNAS: "Nonlinear diffusion and decay of a blob of turbulence spreading into a quiescent fluid." Read the news story from the University of Chicago: "A 'blob' in a tank is helping scientists tease out the secrets of turbulence."

Understanding how turbulence spreads is crucial for many applications, ranging from designing planes and turbines, to building fusion reactors. Until our work, it was not possible to understand the spreading process in a pure way, unaffected by boundaries. With the interest in fusion plasmas, especially in the San Diego area, we hope that our work will have an impact on tokomak design and operation. -- Chancellor's Distinguished Professor of Physics Nigel Goldenfeld
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