In a groundbreaking study, Jason Appelbaum, a Ph.D. candidate in the Wenzel Lab, has made significant strides in understanding turbulent boundary layers. Appelbaum has an outstanding team of researchers. Together, they hope to probe parameter regimes never before touched in the forbidding and alluring world of fluid dynamics. The team’s work represents exciting potential for furthering understanding in applied fields from aerospace engineering to climate science.
This work explores DNS of turbulent flat plate boundary layers at moderate Reynolds numbers. Science in this area has historically been fascinating, but difficult. Appelbaum and his collaborators are running big on the supercomputer frontier. In conjunction with turbulence modeling, they have mounted a direct assault on the challenge of turbulent boundary layers. Based on their analysis, their findings show how data sets previously thought to be distinct— low Reynolds numbers and high— can begin to overlap. This combination provides a much more intuitive picture of turbulence.
Advanced Simulation Techniques
Appelbaum’s team was able to do their research on an eye-popping 1,024 computing nodes. This impressive combination featured more than 130,000 cores across the Hawk supercomputer. Their project was gargantuan. It required more than 100 million CPU hours and in excess of 30 days of computer runtime for the massive, large-scale direct numerical simulation. This very ambitious effort sought to re-construct the time-evolution of a fully-developed turbulent state in detail within a single computational domain.
Appelbaum would go on to explain how the simulation accomplished its most important objective. On top of that, it revealed an inflection point—more clearly than ever before. This inflection point is the beginning of the region of the turbulent boundary layer where self-similarity starts to occur. He likened the concept of self-similarity to realizing that if you just examine the aspect ratio of a photograph. This analogy helps to make the phenomenon more easily understandable in a visual way.
Bridging Knowledge Gaps
Appelbaum and his collaborative research has continued along these lines, pioneering work that builds on the transformative earlier efforts of Christoph and Tobias. They set out to determine how heat transfer and pressure gradients interact to impact turbulence. By incorporating Reynolds effects into their baseline models, the FSD team hopes to make a major step toward state-of-the-art scientific understanding of fluid dynamics.
Appelbaum said that the combination of these concepts will have great scientific impact. Of course, he’s hopeful about what they are going to find. They could provide new understanding of the behavior of turbulent boundary layers in different conditions, a fundamental for engineering and environmental science applications.
Future Directions
Appelbaum, to say the least, is looking forward to it. He predicts important new developments in simulations allowing exploration of larger domains and even more turbulent states. He’s getting ready to release a follow-up paper, so stay tuned. Our new online guide will unpack other findings and ideas from their sweeping research.