CAREER: High-Speed Boundary Layer Transition on Realistic Non-Smooth Surfaces

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). For the design of efficient high-speed vehicles, it is essential to accurately predict the flow field and its interaction with solid surfaces. In the presence of turbulent (non-orderly moving) flow, surface friction and heat transfer are significantly higher than for laminar (orderly moving) flow, leading to performance losses and potentially critical failure. Accurate laminar-to-turbulent transition prediction is a key challenge in fluid dynamics research as it depends on many parameters associated with the geometry, flow conditions, external disturbance environment and smoothness of the surface. At high speeds, exposure to hot, fast-moving flow can lead to severe surface degradation through ablation processes. Therefore, a thorough understanding of how these realistic non-smooth surfaces affect transition is essential for accurate flow predictions. This project addresses a definite gap in fundamental research knowledge by investigating the interaction of time-evolving (ablative) rough surfaces with high-speed transitional flows. This research can have a significant broader positive impact as it can, for example, enable more energy efficient engineering systems involving fluid flows, allow for more efficient space exploration, one day enable commercial hypersonic flight and other forms of high-speed transportation as well as provide rapid response capabilities essential for national security. The project will also encompass significant educational activities encouraging students to pursue careers in STEM disciplines, including computer-based learning experiences used in several outreach efforts with a focus on teaching computational skills.The scientific research objective is to obtain a fundamental understanding of how realistic non-smooth surfaces affect all stages of the laminar-to-turbulent transition process. This project goes well beyond the current state-of-the-art by including the interaction of transitional flows with realistic time evolving (ablative) surfaces. The first ever coupled fluid-ablation interaction simulations considering hypersonic boundary layer transition will be performed. These simulations will provide insight into the intricacies of the complex physical phenomena involved. A unique numerical approach capturing the wide range of temporal and spatial scales will be employed for these simulations and advanced analysis tools, such as modal and bi-orthogonal decomposition, will be used to dissect the complex physics and cultivate understanding of the different effects involving a wide parameter space. This research will yield unprecedented understanding essential for improving transition prediction capabilities and for providing the ability to critically assess the transition process for realistic high-speed flow environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.