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

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。为了设计高效的高速飞行器，准确地预测流场及其与固体表面的相互作用是至关重要的。在湍流(非有序流动)存在的情况下，表面摩擦和换热显著高于层流(有序流动)，从而导致性能损失和潜在的临界失效。准确的层流-湍流过渡预测是流体力学研究中的一个关键挑战，因为它依赖于与几何形状、流动条件、外部扰动环境和表面光滑度有关的许多参数。在高速下，暴露在高温、快速流动中会通过烧蚀过程导致表面严重退化。因此，彻底了解这些逼真的非光滑表面如何影响过渡对于准确的流动预测是至关重要的。该项目通过研究随时间演变的(烧蚀)粗糙表面与高速过渡流动的相互作用，解决了基础研究知识中的一个明确缺口。这项研究可以产生重大的更广泛的积极影响，因为它可以使涉及流体流动的工程系统更节能，允许更有效的空间探索，有朝一日能够实现商业高超声速飞行和其他形式的高速运输，以及提供对国家安全至关重要的快速反应能力。该项目还将包括重要的教育活动，鼓励学生在STEM学科中追求职业生涯，包括在几个以教授计算技能为重点的外展工作中使用的基于计算机的学习经验。科学研究的目标是从根本上了解现实的非光滑表面如何影响从层流到湍流转变过程的所有阶段。这个项目远远超出了目前最先进的水平，包括过渡流与真实时间演变(烧蚀)表面的相互作用。将首次进行考虑高超声速边界层转变的流体-烧蚀相互作用耦合模拟。这些模拟将提供对复杂物理现象的错综复杂的洞察。这些模拟将使用一种独特的数值方法来捕捉广泛的时间和空间尺度，并将使用先进的分析工具，如模态和双正交分解，来剖析复杂的物理现象，并培养对涉及广泛参数空间的不同影响的理解。这项研究将产生前所未有的理解，这对于提高过渡预测能力和提供对现实高速流动环境的过渡过程进行批判性评估的能力至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.