High performance computing methodologies for solving complex turbulent flows

计算流体动力学（CFD）方法是解决工业和环境工程问题的常用工具。由于这些问题大多是紊流的，因此对紊流效应的真实模拟是必要的。基于reynolds - average Navier-Stokes （RANS）的方法已经成为计算湍流的主要方法，特别是在水力学和空气动力学中。然而，RANS模型已经被发现对于大分离的复杂流动和非定常效应不够精确。随着计算机能力的提高和更精确、更高效的数值方法的发展，大涡模拟（LES）方法得到了发展。人们发现LES比RANS优越，但在实际工程问题中部署过于昂贵。一种更实惠的方法结合了RANS和LES的不同优势；由于流太复杂，只能在需要的地方使用LES，而在领域的其他部分，比如靠近墙壁的地方，流是用更便宜的RANS模型计算的。这被称为混合ranss - les方法，这是现代CFD实践的一种有吸引力的方法。本研究计划的重点是基于混合LES-RANS方法的高性能流求解器的开发，以及对现代数值方法的研究，以实现高精度和计算性能。更具体地说，我们将研究过置网格和高阶离散化方法，以实现湍流所需的高精度。这些应用旨在解决水力学和空气动力学工程中遇到的复杂流动问题，例如溢洪道或水坝压力管道上的自由表面流动，以及飞机结构周围的可压缩流动

Computational fluid dynamics (CFD) methods are commonly used as tools for solving industrial and environmental engineering problems. As most of these problems are turbulent, the realistic simulation of the turbulence effect is essential. The Reynolds-Averaged Navier-Stokes (RANS)-based approach has become the workhorse for calculating turbulent flows, especially in hydraulics and aerodynamics. However, RANS models have been found to be not sufficiently accurate for complex flows with large separations and where unsteady effects are of interest. The increase in computer power and the development of more accurate and efficient numerical methods have led to the development of large eddy simulation (LES) methodology. LES has been found superior to RANS, but is too expensive to be deployed in real-scale engineering problems. A more affordable approach combines RANS and LES' different strengths; one can use LES only where needed because the flow is too complex, while in other parts of the domain, such as near walls, the flow is computed with the less expensive RANS model. This has become known as the hybrid RANS-LES approach, which is an appealing methodology for modern CFD practice. This research program is focused on the development of a high performance flow solver based on a hybrid LES-RANS approach and on the investigation of modern numerical methods to allow high accuracy and computational performance. More specifically, we will investigate overset-grid and higher-order discretizations methods to achieve the high accuracy required by turbulent flows. The applications are geared towards solving the complex flow problems encountered in hydraulics and in aerodynamics engineering, such as free surface flows over the spillways or the penstocks of dams, and compressible flows around aircraft structures.**