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

湍流可以是极其复杂的，并且常常不被很好地理解。这种基本认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、运输车辆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）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，DNS在现实场景中在计算上是禁止的。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成本的一小部分捕获详细的物理过程，同时提高非定常湍流预测的准确性。该项目将寻求涉及西班牙裔男女学生;主要研究者积极与几个西班牙裔组织合作，以提高西班牙裔学生的经验，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，用于精确的湍流模拟，其成本仅为DNS的一小部分，并且与其他低阶方法相比具有显着优势，例如大涡模拟（LES），其中计算大尺度湍流并模拟较小尺度。新的方法，被称为选择涡模拟（SES），是基于解决整个频谱的尺度的子集，不像LES，这是有限的低波数。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至关重要的流动中，例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SES的控制参数。SES建模方法将与DNS和LES结果进行比较，以评估精度与计算成本。未解决的模式的研究和建模将提供深入了解能量转移的物理和湍流的动力学一般。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工程应用至关重要的流动。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.