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

湍流可能是极其复杂的，而且往往没有得到很好的理解。这种对基础知识的缺乏限制了我们准确预测气候、污染物在大气和海洋中的扩散，以及设计最佳效率的发动机、交通工具和能源发电系统的能力。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，通过直接数值模拟(DNS)来解析所有相关的湍流尺度来改进在汽车和飞机设计中至关重要的湍流模型，已经取得了重大进展。然而，在现实场景中，域名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的几分之一的成本捕捉详细的物理过程，同时提高非定常湍流预测的精度。该项目将寻求让拉美裔男女学生参与；首席调查员积极与几个拉美裔组织合作，以改善拉美裔学生的体验、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，以仅需一小部分的成本进行精确的湍流模拟，并且与其他低阶方法相比具有显著的优势，如大涡模拟(LES)，后者计算大尺度的湍流，并模拟较小的尺度。这种新的方法被称为选择涡流模拟(SES)，它基于求解整个光谱中的一个尺度子集，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Navier-Stokes方程的真实动力学。这在再现Navier-Stokes动力学方面具有巨大的优势，特别是在小尺度特征非常关键的流动中，如弱扩散组分的混合、小颗粒的扩散、激波和火焰。模型尺度的选择是SES中的控制参数。SES建模方法将与DNS和LES结果进行比较，以评估准确性与计算成本的关系。对未分辨模式的研究和建模将提供对能量传递物理和一般湍流动力学的深入了解。因此，一个成功的SES概念将导致对湍流尺度作用的更全面的了解，以及更准确、可能更便宜的计算工具，可以用于预测和控制对广泛工程应用至关重要的流动。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。

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.