Download or read book A Robust Simplex Cut-cell Method for Adaptive High-order Discretizations of Aerodynamics and Multi-physics Problems written by Huafei Sun and published by . This book was released on 2013 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite the wide use of partial differential equation (PDE) solvers, lack of automation still hinders realizing their full potential in assisting engineering analysis and design. In particular, the process of establishing a suitable mesh for a given problem often requires heavy person-in-the-loop involvement. This thesis presents work toward the development of a robust PDE solution framework that provides a reliable output prediction in a fully-automated manner. The framework consists of: a simplex cut-cell technique which allows the mesh generation process to be independent of the geometry of interest; a discontinuous Galerkin (DG) discretization which permits an easy extension to high-order accuracy; and an anisotropic output-based adaptation which improves the discretization mesh for an accurate output prediction in a fully-automated manner. Two issues are addressed that limit the automation and robustness of the existing simplex cut-cell technique in three dimensions. The first is the intersection ambiguity due to numerical precision. We introduce adaptive precision arithmetic that guarantees intersection correctness, and develop various techniques to improve the efficiency of using this arithmetic. The second is the poor quadrature quality for arbitrarily shaped elements. We propose a high-quality and efficient cut-cell quadrature rule that satisfies a quality measure we define, and demonstrate the improvement in nonlinear solver robustness using this quadrature rule. The robustness and automation of the solution framework is then demonstrated through a range of aerodynamics problems, including inviscid and laminar flows. We develop a high-order DG method with a dual-consistent output evaluation for elliptic interface problems, and extend the simplex cut-cell technique for these problems, together with a metric-optimization adaptation algorithm to handle cut elements. This solution strategy is further extended for multi-physics problems, governed by different PDEs across the interfaces. Through numerical examples, including elliptic interface problems and a conjugate heat transfer problem, high-order accuracy is demonstrated on non-interface-conforming meshes constructed by the cut-cell technique, and mesh element size and shape on each material are automatically adjusted for an accurate output prediction.