Physicists create contained ball of turbulence in a tank

The development will allow them to study a phenomenon that has long been out of reach for scientists.
Loukia Papadopoulos
Turbulence in a tank.jpg

Turbulence is all around us, but it’s been a mystery to scientists for years. Part of the reason is that you can’t disconnect the phenomenon from its source (a spoon needs to stay in a cup of coffee when creating the effect).

Now, a group of physicists from the University of Chicago has finally engineered a way to create turbulence in a water tank by using a ring of jets to blow loops until an isolated “ball” of turbulence forms and stays.

This is according to a press release by the institution published on Thursday.

“It was a surprise to us,” said physicist Takumi Matsuzawa, the first study author describing the findings. 

“It’d be like calmly sitting in a field with a picnic and watching a storm raging 50 feet away,” said Prof. William Irvine, the study's corresponding author.

One of the big open questions

The new development may lead to a method of studying turbulence that can answer long-standing questions.

“It’s often quoted as one of the big open questions in physics,” said Irvine. 

“Turbulence appears everywhere around us, but it keeps eluding what physicists consider a satisfying description,” said Irvine.

 “For example, if you ask, can I predict what happens next when I poke this region of turbulence? The answer is no. Not even really with a supercomputer.” 

Part of the problem with turbulence is that after a few rounds of mixing, it dissipates and stays as a newly formed product. To bypass this issue, the researchers created a box with eight corners containing a vortex ring generator and repeatedly fired rings that met in the center.

They were surprised that they had generated a ball of self-contained turbulence – away from the tank's walls.

“No one knew this was even possible,” said Matsuzawa. “Turbulence is very good at mixing things; if you mix your milk into your coffee, you can only get one or two swirls in before it becomes completely mixed. The fact we can contain it in place is shocking.” 

Their new model can be toyed with to help answer some interesting questions about turbulence.

“How does turbulence dissipate? How does it expand? What does it “remember”? How does the energy spread across scales? Are there different types of turbulence? There are all kinds of questions we could ask, and this is a unique setting with which to ask them,” Irvine said in the statement

“I really hope this can help open up a new playground in the field.”

The study was published in Nature Physics.

Study abstract:

Turbulence is hard to control. Many experimental methods have been developed to generate this elusive state of matter, leading to fundamental insights into its statistical and structural features as well as its onset. In all cases, however, the material boundaries of the experimental apparatus pose a challenge for understanding what the turbulence has been fed and how it would freely evolve. Here we build and control a confined state of turbulence using elemental building blocks—vortex rings. We create a stationary and isolated blob of turbulence in a quiescent environment, initiated and sustained solely by vortex rings. We assemble a full picture of its three-dimensional structure, onset, energy budget and tunability. The incoming vortex rings can be endowed with conserved quantities, such as helicity, which can then be controllably transferred to the turbulent state. Our one-eddy-at-a-time approach opens the possibility for sculpting turbulent flows much as a state of matter, placing the turbulent blob at the targeted position, localizing it and ultimately harnessing it.