At its most basic, turbulence comprises disorderly fluctuations over a wide range of scales in both time and three-dimensional space. These complexities mean that many fundamental aspects are still not understood. Computers can help unravel the mystery, but direct numerical simulations based on exact physical laws have always been very resource-intensive. Their challenges are greatest when investigating rare, very large fluctuations.

Now, Frontier, the world's first — and still fastest — Exascale computer, capable of a quintillion operations per second, is helping researchers to better understand turbulence.

“Turbulence is very complex, theories are incomplete, and laboratory measurements are arduous,” said P.K. Yeung, a professor in the Daniel Guggenheim School of Aerospace Engineering with a courtesy joint appointment in the George W. Woodruff School of Mechanical Engineering. “A world-leading resolution of over 35 trillion grid points on Frontier is expected to lead to new discoveries, which in turn can facilitate advances in modeling where both assumptions and predictions can be tested numerically."

Yeung and his team accessed Frontier, located at the Oak Ridge National Laboratory, when it first went online and also received large allocations of time on the machine from the prestigious INCITE program, which is run by the U.S. Department of Energy's Office of Science. The power of Frontier resides primarily in powerful graphical processing units (GPUs), which compute rapidly. Yeung's group published a journal article that describes a highly successful algorithm specifically designed to take maximum advantage of Frontier's features to make simulations at extremely high resolution feasible and efficient.

“In many scientific fields, people thought calculations of this magnitude were not possible, but now we are there, perhaps earlier than anticipated,” Yeung said. “Our work on turbulence simulations also demonstrates several principles of advanced GPU programming of interest in other fields, especially those where so-called pseudo-spectral methods are important. The science impacts of our extreme scale simulations are expected to be further enhanced by public data-sharing in partnership with the National Science Foundation-supported Johns Hopkins Turbulence Database project."