Selected-Eddy Simulations (SES): a revolutionary approach for turbulence simulations

湍流可以是极其复杂的，而且往往不能很好地理解。缺乏基本的认识限制了我们准确预测气候、污染物在大气和海洋中的扩散，以及设计最高效的发动机、交通工具和能源生产系统的能力。湍流具有广泛的尺度，这使得实验测量和计算预测具有挑战性。在过去的40年里，直接数值模拟（DNS）已经取得了重大进展，它解决了所有相关的湍流尺度，以改进在汽车和飞机设计中至关重要的湍流模型。然而，在实际场景中，DNS在计算上是令人望而却步的。该项目的主要目标是开发一种潜在的变革性方法来模拟湍流，以DNS的一小部分成本捕获详细的物理，同时提高非定常湍流预测的准确性。该项目将寻求西班牙裔男女学生的参与；首席研究员积极与几个西班牙裔组织合作，以提高西班牙裔学生的经历，教育和校园生活质量。该项目旨在开发一种革命性的新方法，以精确的湍流模拟，其成本仅为DNS的一小部分，并且与其他低阶方法（如大涡模拟（LES））相比具有显着优势，后者计算大尺度湍流并模拟较小尺度。这种新方法被称为“选择涡模拟”（SES），它基于解决整个频谱尺度的子集，而不像LES那样仅限于低波数。因此，SES在所有尺度的子集上使用了Navier-Stokes方程的真正动力学。这在重现Navier-Stokes动力学方面具有巨大的优势，特别是在小尺度特征至关重要的流动中，如弱扩散物质的混合、小颗粒的分散、冲击和火焰。模型尺度的选择是系统的控制参数。SES建模方法将与DNS和LES结果进行比较，以评估准确性和计算成本。对未解析模态的研究和建模将提供对能量传递物理学和一般湍流动力学的见解。因此，一个成功的SES概念将导致对湍流尺度的作用的更全面的理解，以及一个更准确、可能更便宜的计算工具，可用于预测和控制对广泛的工程应用至关重要的流动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Turbulent flows can be extremely complex and often not well understood. This lack of fundamental understanding limits our ability to accurately predict the climate, dispersion of pollutants in the atmosphere and the ocean, and to design optimally efficient engines, transportation vehicles, and energy generation systems. Turbulence has a wide range of scales which makes experimental measurements and computational predictions challenging. Over the past 4 decades, significant progress has been made through direct numerical simulations (DNS) which resolve all relevant turbulent scales to improve turbulence models that are critical in automotive and aircraft design. However, DNS are computationally prohibitive in realistic scenarios. The main objective of this project is to develop a potentially transformative approach to simulate turbulent flows, capturing the detailed physics at a fraction of the cost of DNS while improving the accuracy of unsteady turbulent predictions. The project will seek to involve Hispanic men and women students; the principal investigator actively collaborates with several Hispanic organizations to enhance Hispanic students’ experiences, education, and quality of life on campus. This project aims to develop a revolutionary new approach for accurate turbulence simulations at a fraction of the cost DNS and with significant advantages over other low-order approaches such as Large-Eddy Simulations (LES), where large-scale turbulence is computed and smaller scales are modelled. The new approach, termed Selected-Eddy Simulations (SES), is based on solving a subset of scales across the entire spectrum, unlike LES which is limited to low wavenumbers. Thus, SES uses the true dynamics of the Navier-Stokes equations over a subset of all scales. This has tremendous advantages in reproducing Navier-Stokes dynamics especially in flows where small-scale features are critical such as mixing of weakly diffusive species, dispersion of small particles, shocks, and flames. The selection of modeled scales are control parameters in SES. The SES modeling approach will be compared with DNS and LES results to assess accuracy versus computational cost. The study and modeling of unresolved modes will provide insights into the physics of energy transfer and the dynamics of turbulence in general. Thus, a successful SES concept will result in a more complete understanding of the role of turbulent scales and a more accurate, potentially less expensive, computational tool that can be used to predict and control flows critical for a wide range of engineering applications.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.