High-Order AFEM for the Laplace–Beltrami Operator: Convergence Rates

We present a new AFEM for the Laplace–Beltrami operator with arbitrary polynomial degree on parametric surfaces, which are globally \(W^1_\infty \) and piecewise in a suitable Besov class embedded in \(C^{1,\alpha }\) with \(\alpha \in (0,1]\). The idea is to have the surface sufficiently well resolved in \(W^1_\infty \) relative to the current resolution of the PDE in \(H^1\). This gives rise to a conditional contraction property of the PDE module. We present a suitable approximation class and discuss its relation to Besov regularity of the surface, solution, and forcing. We prove optimal convergence rates for AFEM which are dictated by the worst decay rate of the surface error in \(W^1_\infty \) and PDE error in \(H^1\).     

Dynamically adaptive tree grid modeling for simulation and visualization of rainwater overland flow

Modeling and visualization of a rainwater overland flow is an important tool for a risk assessment, preparation, evacuation planning, and real‐time forecasting of flood warning. The objective of this research is to develop a numerical software to visualize the rainwater overland flow based on a finite volume method for shallow water equations and in combination with the dynamically adaptive tree grid technique and the dynamic domain‐defining method. The obtained simulations for several experiments were tested and compared with results in literature, both theoretical and experimental results. The comparisons with non‐adaptive grids show that the developed algorithm for simulation is very efficient and has a potential for practical usages, in terms of computational times and accuracy. Copyright © 2015 John Wiley & Sons, Ltd.