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Leibner, Tobias: Model reduction for kinetic equations: moment approximations and hierarchical approximate proper orthogonal decomposition. 2021
Inhalt
Abstract
Contents
List of Figures
Introduction
Collaborations and previous publications
Notation
Kinetic equations
General kinetic transport equations
Radiative transfer
Moment models
Linear closure
Minimum-entropy closures
First-order finite element moment models
Angular bases in slab geometry
Full moments
Continuous piecewise linear angular basis (hat functions)
Partial moments (discontinuous-Galerkin ansatz)
Angular bases in three dimensions
Barycentric-coordinate basis functions (hat functions)
Partial moments on the unit sphere
Realizability
Structure of the realizable sets
Slab geometry (one dimension)
Three dimensions
Numerically realizable set
Numerical results
Slab geometry (one dimension)
Three dimensions
Computational complexity
Realizability-preserving finite volume schemes
First-order realizability-preserving finite volume scheme
Finite volume grid
Finite volume scheme
Second-order realizability-preserving splitting scheme
Source system
Flux system
Time step restriction
Implementation details
Solving the optimization problem
Solving the eigenvalue problems
Realizability limiting
Implementation of quadrature rules
Numerical results
Slab geometry (one dimension)
Three dimensions
Quadrature sensitivity
Timings
New numerical scheme based on variable transformation
New scheme in transformed variables
Numerical results
Convergence
Performance
Parallel scaling
Masslumping
Hierarchical approximate proper orthogonal decomposition
Related work
Reduced basis methods
General setting
Reduced basis method for moment models
Proper orthogonal decomposition
Definition of the HAPOD
Special cases: distributed and incremental HAPOD
Main theorems
Algorithmic benefits
Proofs of main theorems
Reduction of a large linear moment model
Conclusion and Outlook
First-order finite element-based moment models
Transformed numerical scheme
Reduced-basis methods for moment models
Appendix
Explicit formulas for integrals
Mass and flux matrices
Source-beam boundary values
Minimum-entropy models in slab geometry
Additional figures and data for the variable-transformed scheme
Bibliography
Glossaries
List of Symbols
List of Acronyms