Higher order accurate bounds preserving time-implicit discretizations for the nonlinear time-dependent equations
Prof. Yan Xu
University of Science and Technology of China

In this talk, we discuss local discontinuous Galerkin (LDG) method for solving the nonlinear time-dependent equations. The space discretization results in an extremely local, element based discretization, which is bene ficial for parallel computing and maintaining high order accuracy on unstructured meshes. We also develop a novel semi-implicit spectral deferred correction(SDC) time marching method. The method can be used in a large class of problems, especially for highly nonlinear ordinary differential equations (ODEs) without easily separating of stiff and non-stiff components, which is more general and efficient comparing with traditional semi-implicit SDC methods. The proposed semi-implicit SDC method is based on low order time integration methods and corrected iteratively. The order of accuracy is increased for each additional iteration. This SDC method is intended to be combined with the method of lines, which provides a  flexible framework to develop high order semi-implicit time marching methods for nonlinear partial differential equations (PDEs). Coupled with the LDG spatial discretization, the fully discrete schemes are all high order accurate in both space and time,and stable numerically with the time step proportional to the spatial mesh size. Using Lagrange multipliers the conditions imposed by the positivity preserving limiters are directly coupled to a DG discretization combined with implicit time integration method. The positivity preserving DG discretization is then reformulated as a Karush-Kuhn-Tucker (KKT) problem. We therefore develop an ecient active set semi-smooth Newton method that is suitable for the KKT formulation of time-implicit positivity preserving DG discretizations. Convergence of this semi-smooth Newton method is proven using a specially designed quasi-directional derivative of the time-implicit positivity preserving DG discretization. The higher order bounds preserving numerical schemes for the reactive Euler equations are presented. Numerical experiments are carried out to illustrate the accuracy and capability of the proposed method.

About the Speaker

徐岩,中国科学技术大学数学科学学院教授。2005年于中国科学技术大学数学系获计算数学博士学位。2005-2007年在荷兰Twente大学从事博士后研究工作。2009年获得德国洪堡基金会的支持在德国Freiburg大学访问工作一年。主要研究领域为高精度数值计算方法。2008年度获全国优秀博士学位论文奖,2017年获国家自然科学基金委“优秀青年基金”。徐岩教授入选了教育部新世纪优秀人才计划,主持国家自然科学基金面上项目、德国洪堡基金会研究组合作计划(Research Group Linkage Programme)、霍英东青年教师基础研究课题等科研项目。担任Journal of Scientific Computing, Advances in Applied Mathematics and Mechanics, Communication on Applied Mathematics and Computation、计算物理等杂志的编委。

2021-02-22 9:00 AM
Room: Tencent Meeting
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