EAGER: Liutex-based Sub-Grid Model for Large Eddy Simulation of Turbulent Flow

EAGER：基于 Liutex 的湍流大涡模拟子网格模型

• 批准号: 2422573
• 负责人: Yifei Yu
• 金额: $ 29.96万
• 依托单位: University of Texas at Arlington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2422573&HistoricalAwards=false
• 关键词: EAGER; Liutex; based; Sub; Grid

An efficient, practical, and accurate numerical simulation method for turbulent flow is important in computational fluid dynamics for the study of tornadoes, hurricanes, aircraft design, and other turbulence-related areas. Due to the limitation of computation resources, it is hard to numerically resolve all-size vortices. Scientists have found that small-scale vortices have similarities although large-scale vortices are quite different. Large eddy simulation only resolves large-scale vortices and leaves sub-grid scales for modeling. Therefore, the accuracy of large eddy simulations is determined by the sub-grid models. The concept of eddy viscosity is still adopted in most practical turbulent flow simulations. However, most of the existing sub-grid models still use the resolved shear to calculate the eddy viscosity, which is inconsistent with the physics, especially in the shear-dominated regions like the laminar sublayer in turbulent boundary layers, where vorticity/shear is large, but eddy viscosity is zero. The inconsistency is caused by the misunderstanding that vortex strength is measured by vorticity. The remedy of using a wall function or artificial adjustment near the wall region cannot solve the consistency problem. Liutex is a new physical quantity exactly representing the direction and strength of a vortex or eddy. Previous direct numerical simulation has shown that Liutex has similarity in the dissipation subregion of the turbulent boundary layer, which paves the foundation for constructing a new sub-grid model by using Liutex.This project aims to develop a reliable and efficient Liutex-based sub-grid model for the large eddy simulation community. Liutex is a rigorous mathematical definition of vortex that correctly distinguishes fluid rotation and shear. The introduction of Liutex to extract the rigid rotation from the fluid velocity gradient is groundbreaking work in turbulence research. So, modeling small-scale vortices using Liutex instead of shear is very reasonable as eddy is vortex and vortex is Liutex. This project plans to (1) develop a new Liutex-based sub-grid model, (2) develop a new dynamic Liutex-based sub-grid model, (3) test new models in a variety of computational fluid dynamics cases such as backward step flow, S-duct flow, and flow around an airfoil, (4) evaluate the effect of new Liutex-based sub-grid model and compare it with other existing sub-grid models. The code of the new model will be provided to the community through GitHub. As large eddy simulation becomes one of the major tools of computational fluid dynamics, a breakthrough in the development of the sub-grid models will benefit almost all fluid-related research areas and engineering applications in multi-disciplinary research areas including aerodynamics, hydrodynamics, meteorology (hurricanes and tornadoes for example), bio-flow (blood flow and respiratory flow for example), astronomy (sun storm for example), etc.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.

对于龙卷风，飓风，飞机设计和其他与湍流相关的区域的研究，一种有效，实用和准确的数值模拟方法在计算流体动力学中很重要。由于计算资源的限制，很难在数值上解析全尺寸涡流。科学家发现，小型涡旋具有相似性，尽管大规模涡流却大不相同。大型涡流模拟只能解析大规模的涡旋和叶子亚网格尺度进行建模。因此，大型涡流模拟的精度由子网格模型确定。在大多数实用的湍流模拟中，涡流粘度的概念仍然采用。但是，大多数现有的子网格模型仍然使用已解决的剪切来计算涡质粘度，这与物理学不一致，尤其是在剪切主导的区域（如在湍流边界层中的层层覆盖层），其中涡度/剪切量很大，但涡流粘度很大。不一致是由于误解是通过涡度来衡量涡旋强度的误解。在墙壁区域附近使用墙壁功能或人工调整的补救措施无法解决一致性问题。 liutex是一个新的物理量，准确代表了涡流或涡流的方向和强度。先前的直接数值模拟表明，liutex在湍流边界层的耗散子区域中具有相似性，这为通过使用liutex构建新的子网格模型的基础铺平了基础。该项目旨在为大型EDDY模拟社区开发一个可靠且有效的基于LIUTEX的子网格模型。 liutex是对涡旋的严格数学定义，可以正确区分流体旋转和剪切。从流体速度梯度中提取刚性旋转的Liutex引入了湍流研究中的开创性工作。因此，使用liutex代替剪切的小规模涡流建模非常合理，因为涡流是涡流，而涡流为liutex。该项目计划（1）开发一个新的基于LIUTEX的子网格模型，（2）开发一种新的基于LIUTEX的基于LIUTEX的子网格模型，（3）在各种计算流体动力学案例中测试新模型，例如向后台阶流，S导管流量，S-Duct Flow和Airfoil围绕机翼流动，（4）评估基于LIUTEX的基于Liutex的基于Sub-Grid模型的效果，并将其与其他现有的Sub-Grid模型相结合。新模型的代码将通过GitHub提供给社区。随着大型涡流模拟成为计算流体动力学的主要工具之一，子网格模型的开发中的突破将使几乎所有与流体相关的研究领域以及多学科研究领域中的所有与流体相关的研究领域以及工程应用，包括空气动力学，流动动力学，气象学，气象学（例如飓风和龙卷风），示例和呼吸道（示例）（示例）（示例）（示例）奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响审查标准评估值得支持。