报告人：吴子牛教授 (清华大学航天航空学院)

吴子牛教授简介：1985年获得北京航空学院空气动力学学士学位，1988年获得法国ECPC传热与燃烧深入研究文凭，1992年获得居里大学力学博士学位，1994年回国后分别任教于北京航空航天大学和清华大学，2001年清华大学工程力学系长江学者特聘教授。主要从事空气动力学教学与人才培养、学术研究和相关工程问题计算分析与软件开发。从2000年开始研究高超声速空气动力学问题，包括气动力、气动热和稀薄效应，尤其涉及其中的激波与膨胀波，包括两种基本结构之间以及与其它结构的干扰,其它问题包括非定常空气动力学问题以及一般空气动力学问题的计算与分析。在Journal of Fluid Mechanics发表以空气动力学为主的论文共12篇。为相关航空航天单位研制软件约10套，分别在相关航空航天单位获得应用。除空气动力学教学、人才培养、学术研究和工程服务外，还广泛参与学术与社会服务工作。作为秘书长组织过近10次国内国际会议。目前为航空学报英文版(SCI一区期刊)副主编。担任航空学报高超专辑(2015年1月)特邀主编。                      

报告内容：突然启动问题在气动弹性、扑翼飞行、控制面操作以及阵风作用等方面有应用价值。在大攻角情况下，低速问题涉及大尺度旋涡生成与运动，高速问题涉及激波与稀疏波及其干扰。在本研究中，气动特性与旋涡以及激波膨胀波之间的演化进行解析关联。对于低速问题，提出了气动力释放、增强、失速和恢复四阶段模型。尤其揭示了失速来源于尾涡上洗的机制。在高速情况下，得到了定常波与非定常波相互干扰对压力分布与气动力演化的准解析表达式。

 

 

第二个学术报告：Status and Trend of Unstructured Grid Methods for Computational Fluid Dynamics

North Carolina State University )

报告人简介：Dr. Hong Luo is a professor in the Department of Mechanical and Aerospace Engineering at North Carolina State University. He received his Ph.D. in Applied Mathematics from Pierre and Marie Curie University (University of Paris 6) in France in 1989. His current research interests include:  Computational Fluid Dynamics, Computational Aeroacoustics, and Computational mgnetohydrodynamics; Reconstructed Discontinuous Galerkin Methods on Unstructured Hybrid Grids; High Performance Computing on Hybrid CPU/GPU Architectures; Moving Boundary Problems and Fluid-Structure Interaction; Large Eddy Simulation of Turbulent Flows; Multi-phase Flows and Chemically Reactive Flows; Geometry Modeling, Unstructured Grid Generation, and Grid Adaptation. His research activities have been and are supported by NASA, AFSOR, DOE, Idaho National Laboratory, Navy, Army, NSF, DTRA, and others. Prof. Luo has over 200 papers to his credit.

 

报告内容：The current status for the efficient simulation and analysis of flow problems using a second-order finite volume (FV) method on unstructured grids is briefly reviewed. It is concluded that all major areas required in the analysis cycle - grid generation, flow solvers, and visualization - have seen major advances in recent years, allowing us to produce high-quality solutions for a variety of flow problems around complex geometries in a matter of hours. The presentation will then be focused on the development of a higher-order reconstructed discontinuous Galerkin (DG) method for computational fluid dynamics (CFD). The idea behind rDG methods is to combine the efficiency of the reconstruction methods in FV methods and the accuracy of the DG methods to obtain a better numerical algorithm in CFD. The beauty of the resulting rDG methods is that they provide a unified formulation for both FV and DG methods, and contain both classical FV and standard DG methods as two special cases of the rDG methods, and thus allow for a direct efficiency comparison. In our latest work, a rDG method based on a Hierarchical WENO reconstruction, termed HWENO(P₁P₂), designed not only to enhance the accuracy of DG methods but also to ensure the nonlinear stability of the rDG method, is presented to solve compressible flow problems at all speeds on hybrid grids. The developed HWENO(P₁P₂) method is used to compute a variety of flow problems on hybrid meshes to demonstrate its accuracy, robustness, and non-oscillatory property. The numerical experiments indicate that the HWENO(P₁P₂) method is able to capture shock waves within one cell without any spurious oscillations, and achieve the designed third-order of accuracy: one order accuracy higher than the underlying DG method, indicating the potential of this rDG method to become a viable, competitive, and perhaps superior DG method over existing FV and DG methods for CFD. Extension of the rDG methods to the incompressible flows, hyperbolic diffusion equation, Magnetohydrodynamics, and the porting of the rDG methods on GPUs will also be presented and discussed.