An Unexpected Twist Lights Up the Secrets of Turbulence

[Elderberry]

Quanta Magazine 9/3/2020

Having solved a central mystery about the “twirliness” of tornadoes and other types of vortices, William Irvine has set his sights on turbulence, the white whale of classical physics.

It’s time to feed the blob. Seething and voracious, it absorbs eight dinner-plate-size helpings every few seconds.

The blob is a cloud of turbulence in a large water tank in the lab of the University of Chicago physicist William Irvine. Unlike every other instance of turbulence that has ever been observed on Earth, Irvine’s blob isn’t a messy patch in a flowing stream of liquid, gas or plasma, or up against a wall. Rather, the blob is self-contained, a roiling, lumpy sphere that leaves the water around it mostly still. To create it and sustain it, Irvine and his graduate student Takumi Matsuzawa must repeatedly shoot “vortex loops” — essentially the water version of smoke rings — at it, eight loops at a time. “We’re building turbulence ring by ring,” said Matsuzawa.

Irvine and Matsuzawa tightly control the loops that are the blob’s building blocks and study the resulting confined turbulence up close and at length. The blob could yield insights into turbulence that physicists have been chasing for two centuries — in a quest that led Richard Feynman to call turbulence the most important unsolved problem in classical physics. (Quantum turbulence has become an important problem too.) Untangling turbulence might also prove extraordinarily impactful, given that it plays a huge role in stars, aviation, nuclear fusion, weather, changes in the Earth’s core, wind turbines and even human health — arterial flow can become dangerously turbulent.

If the blob does yield big advances in turbulence, it will add to the growing string of surprising and influential breakthroughs that Irvine and his students have produced in the physics of what might loosely be called spinning stuff — systems composed of whirling objects, fluids and even fields.

Especially attention-grabbing among Irvine’s findings has been the lab’s contribution to fluid dynamics, an area that has been notorious for painfully slow progress, in part because of the difficulty of collecting good data. The most prominent breakthrough involves proving a fundamental new law governing the tornado-like tubes of currents known as vortices. The law illuminates how these fundamental phenomena form, interact, evolve and decay. “Science often involves finding a way to tweak or fill a small gap in what’s been done,” said Daniel Lathrop, a University of Maryland physicist specializing in nonlinear dynamics who is familiar with Irvine’s work. “William asks what he can do that’s completely different than what’s been done. It’s the sort of work that can open new fields.”

But now that his mastery of vortices has led him to the blob, Irvine senses even bigger — and more dangerous — prey in the water. “Because of the absence of good data and theory, turbulence has been considered the place where careers go to die,” said Irvine. “I find myself getting more and more into it.”

More: https://www.quantamagazine.org/an-unexpected-twist-lights-up-the-secrets-of-turbulence-20200903/