“Unprecedented Achievement: Scientists Generate Self-Contained Turbulent Sphere”

“Unprecedented Achievement: Scientists Generate Self-Contained Turbulent Sphere”

A groundbreaking development by researchers at the University of Chicago has led to the successful creation of a self-contained “sphere” of turbulence within a water-filled tank, marking the first occasion such an event has been realized. A visual representation illustrates the temporal fluctuations of the sphere’s average energy density. Credit goes to Takumi Matsuzawa for this visualization.

This novel accomplishment could shed light on numerous unresolved queries concerning the nature of turbulence.

Turbulence is an omnipresent phenomenon, manifesting in a variety of contexts, from the aerodynamic interactions affecting cars and airplanes to the intermingling of milk and coffee in your cup, and even in the cardiovascular dynamics post-valve closure. Despite its prevalence, our understanding of turbulence remains incomplete.

Traditionally, physicists have preferred to investigate phenomena in isolated settings, devoid of external influences. However, turbulence is an exception, as external variables, like the stirring implement in a liquid, play a crucial role in shaping the behavior of the turbulent system. The isolation of turbulence as an independent variable has, until now, proven to be a challenge.

A research team from the University of Chicago has innovated a method to produce self-contained turbulence within a water tank by using an array of jets that circulate fluid until a detached “sphere” of turbulence emerges and is maintained.

“Discovering this was entirely unexpected,” remarked Takumi Matsuzawa, the lead author of the study, published in Nature Physics. According to Prof. William Irvine, the senior author, “It resembles observing a violent storm from the tranquil confines of a pastoral setting.”

This breakthrough offers a promising avenue for the comprehensive study of turbulence.

“It was unimaginable that this could be achieved,” commented Matsuzawa, a graduate student in physics.

Turbulence—characterized by chaotic flow in a non-uniformly mixed medium—remains one of the elusive challenges in the realm of physics, according to Irvine.

While strides have been made in characterizing an “ideal” state of turbulence, devoid of complicating factors such as boundaries or variations in energy and time, much about real-world turbulence is yet to be understood.

Experimental challenges have also been a hurdle. Methods for generating turbulence, whether by propelling water at high velocity through a tube or employing a paddle to agitate water, usually encounter confounding variables like interaction with the container walls and the stirring device, which affect the outcomes.

Matsuzawa, Irvine, and their colleagues had previously been conducting experiments involving water tanks to produce “vortex rings,” akin to smoke rings but in a liquid medium. During their attempts to combine these to generate turbulence, the energy often rebounded, failing to form a stable turbulent state.

However, a specific arrangement, featuring an octagonal box each corner of which housed a vortex ring generator, yielded an unexpected result: firing vortex rings that converged at the center resulted in the formation of a self-contained turbulent sphere, isolated from the tank walls.

“This was a milestone in itself, as no one had thought this was conceivable,” stated Matsuzawa. The unique structure of the self-contained turbulent sphere allows researchers to employ lasers and high-speed cameras to meticulously track various parameters, including energy and helicity, as well as impulse and angular impulse, the fluid analogs of momentum and angular momentum.

Furthermore, the scientists were able to manipulate the turbulent sphere by altering specific parameters, such as the helicity or energy input, and could observe its subsequent evolution.

Irvine elaborated, “The newly developed method enables us to pose a myriad of questions about the characteristics of turbulence, from its dissipation and expansion to its ‘memory’ and energy distribution across scales. This presents a remarkable new platform for exploration in the field.”

Reference: “Creation of an Isolated Turbulent Blob Fed by Vortex Rings” by Takumi Matsuzawa, Noah P. Mitchell, Stéphane Perrard, and William T. M. Irvine, published on May 11, 2023, in Nature Physics.
DOI: 10.1038/s41567-023-02052-0

Frequently Asked Questions (FAQs) about Self-Contained Turbulence

More about Self-Contained Turbulence

• Nature Physics Journal Article
• University of Chicago Physics Department
• Exploring the Complexities of Turbulence
• Takumi Matsuzawa Research Profile
• Prof. William Irvine Faculty Page
• Breakthroughs in Fluid Dynamics
• Introduction to Turbulence
• FAQ on Turbulence
• Physics Today: Current Research Highlights