CAREER: Turbulence-Resolving Integral Simulations for Boundary Layer Flows

湍流在与能源、交通和国家安全有关的各种边界层流中起着关键的物理作用。因此，提高边界层湍流的模拟能力是加快工程设计、优化和认证，同时降低相关成本的关键。应用实例包括模拟湍流对飞机或风力涡轮机叶片上气动力的影响，以及高超声速飞行器的强烈气动加热。尽管超级计算机的性能取得了巨大进步，但仅使用基本物理定律对这些流动和其他类似重要流动进行直接模拟，通常要么不切实际，要么完全不可行。这一困难是由于湍流涡旋运动可能具有的大范围尺寸相关的极高的计算要求。因此，需要创新的近似方法来创建实用的仿真工具，在不牺牲太多精度的情况下减少计算成本。该项目引入了一种新的模拟框架，该框架基于对流动的二维表示中最大、最有影响的湍流运动的直接解析。该方法将首先针对低速流动进行开发，然后将其扩展到解决与高超声速飞行器边界层有关的挑战。从技术角度来看，开发具有潜在变革性的模拟框架可以影响与社会最紧迫的挑战相关的各种应用。课堂内外的创新教育活动将与该项目的研究活动相结合。该项目的总体目标是引入和开发用于计算湍流边界层动力学的湍流分解积分模拟。虽然基于积分的方法已经很好地应用于边界层，但现有的方法是基于平均方程的。提出的模拟框架将考虑基于积分的模拟，直接解决湍流边界层的二维描述中的大范围和超大规模运动，这将是新的突破。在确定了该方法的基本能力后，将特别注意现有建模技术有较大困难的场景，包括承受非零自由流压力梯度的边界层和具有高焓效应的高超声速边界层。在评估新模拟方法的成功时，将特别注意物理保真度和计算效率之间的权衡。综合教育活动将形成一个多管齐下的努力，以拓宽从本科生到研究生的渠道，并提高学生进入研究生院的准备和流体动力学科学计算的能力。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。

Turbulence plays a key physical role in a wide variety of boundary layer flows related to energy, transportation, and national security. As such, improving simulation capabilities for boundary layer turbulence holds the key to accelerating engineering design, optimization, and certification while reducing associated costs. Example applications include the modeling the impact of turbulence on aerodynamic forces on airplanes or wind turbine blades, and the intense aerodynamic heating of hypersonic vehicles. Despite enormous advances in supercomputer performance, direct simulations of these and other similarly important flows, using only the basic laws of physics, are typically either impractical or completely infeasible. This difficulty is due to the extremely high computational requirements associated with wide range of sizes that turbulent eddying motions can have. As a result, innovative approximation methods are required to create practical simulation tools by reducing computational cost without sacrificing too much accuracy. This project introduces a new simulation framework based on the direct resolution of the largest, most influential turbulent motions within a two-dimensional representation of the flow. The method will be developed first for low-speed flows before extending it to tackle challenges related to boundary layers on hypersonic vehicles. From a technical perspective, the development of a potentially transformative simulation framework can impact a wide variety of applications related to society’s most pressing challenges. Innovative educational activities within and outside the classroom will be integrated with the research activities of the project.The overarching goal of the project is to introduce and develop turbulence resolving integral simulations for computing turbulent boundary layer dynamics. While integral-based methods have been well established for use with boundary layers, existing approaches are based on averaged equations. The proposed simulation framework will break new ground by considering integral-based simulations that directly resolve large and very-large scale motions in a two-dimensional description of the turbulent boundary layer. After establishing the basic competence of the approach, particular attention will be given to scenarios for which existing modeling techniques have greater difficulty, including boundary layers subjected to non-zero freestream pressure gradients and hypersonic boundary layers with high-enthalpy effects. In evaluating the success of the new simulation method, particular attention will be given to the trade-off between physical fidelity and computational efficiency. Integrated educational activities will form a multi-pronged effort to broaden the undergraduate-to-graduate pipeline and improve student readiness for graduate school and competence in scientific computing for fluid dynamics.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.