Flowing

One way to reduce the consumption of liquid fossil fuels is to improve combustion efficiency. Such improvements would mean engines like those in gasoline and diesel powered vehicles would use less fuel to achieve the same outcome. However, this requires a better understanding of the complex physical processes involved in the spray combustion of liquid fuels, says Antonino Ferrante of the University of Washington.

Most spray combustion devices operate in the turbulent regime. The vaporization rate of fuel droplets is recognized as a key mechanism in fuel droplet combustion, making the effects of droplet vaporization on the dynamics of turbulence important, he explains. However, the underlying physical mechanisms are largely unknown. But his work is bringing us closer to an answer.

For four years, Ferrante and his team have used a variety of National Science Foundation-funded resources to perform direct numerical simulations (DNS) of droplet-laden isotropic turbulence, and particle-laden spatially developing turbulent boundary layers. By using Kraken at the National Institute for Computational Sciences (NICS) and Ranger at the Texas Advanced Computing Center (TACC), the Ferrante team was able to perform DNS of particle-laden turbulent flows at Reynolds numbers based on the momentum thickness larger than 2,900, and DNS of droplet-laden isotropic turbulence with thousands of fully-resolved droplets. With assistance from NCSA research programmer Darren Adams, among others, the team was able to not only scale their code to use nearly 5,000 cores on Kraken, they were also able to optimize the code to run on large core counts on Ranger. NCSA visualization programmer Dave Bock then translated the results into meaningful visual images like the one shown here.

The Ferrante team’s work has been published in numerous journals, including the Journal of Fluid Mechanics, the Physics of Fluids, the Journal of Turbulence, and the Journal of Computational Physics. They have also presented at many conferences, including the 23rd International Conference of Theoretical and Applied Mechanics (ICTAM) in Bejing in 2012.

With the launch of Blue Waters, Ferrante hopes to make even more progress in determining the physical mechanisms occurring in evaporating droplet-laden turbulence. He is using a CAREER award from NSF to develop a petascale DNS code that will simulate evaporating droplets in isotropic turbulence.

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