Adaptive Mesh Refinement - Theory and Applications

Adaptive Mesh Refinement - Theory and Applications
Author: Tomasz Plewa
Publisher: Springer Science & Business Media
Total Pages: 550
Release: 2005-12-20
Genre: Mathematics
ISBN: 3540270396

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Advanced numerical simulations that use adaptive mesh refinement (AMR) methods have now become routine in engineering and science. Originally developed for computational fluid dynamics applications these methods have propagated to fields as diverse as astrophysics, climate modeling, combustion, biophysics and many others. The underlying physical models and equations used in these disciplines are rather different, yet algorithmic and implementation issues facing practitioners are often remarkably similar. Unfortunately, there has been little effort to review the advances and outstanding issues of adaptive mesh refinement methods across such a variety of fields. This book attempts to bridge this gap. The book presents a collection of papers by experts in the field of AMR who analyze past advances in the field and evaluate the current state of adaptive mesh refinement methods in scientific computing.

Adaptive Mesh Refinement Method for CFD Applications

Adaptive Mesh Refinement Method for CFD Applications
Author: Oscar Luis Antepara Zambrano
Publisher:
Total Pages: 158
Release: 2019
Genre:
ISBN:

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The main objective of this thesis is the development of an adaptive mesh refinement (AMR) algorithm for computational fluid dynamics simulations using hexahedral and tetrahedral meshes. This numerical methodology is applied in the context of large-eddy simulations (LES) of turbulent flows and direct numerical simulations (DNS) of interfacial flows, to bring new numerical research and physical insight. For the fluid dynamics simulations, the governing equations, the spatial discretization on unstructured grids and the numerical schemes for solving Navier-Stokes equations are presented. The equations follow a discretization by conservative finite-volume on collocated meshes. For the turbulent flows formulation, the spatial discretization preserves symmetry properties of the continuous differential operators and the time integration follows a self-adaptive strategy, which has been well tested on unstructured grids. Moreover, LES model consisting of a wall adapting local-eddy-viscosity within a variational multi-scale formulation is used for the applications showed in this thesis. For the two-phase flow formulation, a conservative level-set method is applied for capturing the interface between two fluids and is implemented with a variable density projection scheme to simulate incompressible two-phase flows on unstructured meshes. The AMR algorithm developed in this thesis is based on a quad/octree data structure and keeps a relation of 1:2 between levels of refinement. In the case of tetrahedral meshes, a geometrical criterion is followed to keep the quality metric of the mesh on a reasonable basis. The parallelization strategy consists mainly in the creation of mesh elements in each sub-domain and establishes a unique global identification number, to avoid duplicate elements. Load balance is assured at each AMR iteration to keep the parallel performance of the CFD code. Moreover, a mesh multiplication algorithm (02) is reported to create large meshes, with different kind of mesh elements, but preserving the topology from a coarser original mesh. This thesis focuses on the study of turbulent flows and two-phase flows using an AMR framework. The cases studied for LES of turbulent flows applications are the flow around one and two separated square cylinders, and the flow around a simplified car model. In this context, a physics-based refinement criterion is developed, consisting of the residual velocity calculated from a multi-scale decomposition of the instantaneous velocity. This criteria ensures grid adaptation following the main vortical structures and giving enough mesh resolution on the zones of interest, i.e., flow separation, turbulent wakes, and vortex shedding. The cases studied for the two-phase flows are the DNS of 2D and 3D gravity-driven bubble, with a particular focus on the wobbling regime. A study of rising bubbles in the wobbling regime and the effect of dimensionless numbers on the dynamic behavior of the bubbles are presented. Moreover, the use of tetrahedral AMR is applied for the numerical simulation of gravity-driven bubbles in complex domains. On this topic, the methodology is validated on bubbles rising in cylindrical channels with different topology, where the study of these cases contributed to having new numerical research and physical insight in the development of a rising bubble with wall effects.

Cartesian CFD Methods for Complex Applications

Cartesian CFD Methods for Complex Applications
Author: Ralf Deiterding
Publisher: Springer Nature
Total Pages: 144
Release: 2021-04-03
Genre: Mathematics
ISBN: 3030617610

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This volume collects the most important contributions from four minisymposia from ICIAM 2019. The papers highlight cutting-edge applications of Cartesian CFD methods and describe the employed algorithms and numerical schemes. An emphasis is laid on complex multi-physics applications like magnetohydrodynamics, combustion, aerodynamics with fluid-structure interaction, solved with various discretizations, e.g. finite difference, finite volume, multiresolution or lattice Boltzmann CFD schemes. Software design aspects and parallelization challenges are also considered. The book is addressed to graduate students and scientists in the fields of applied mathematics and computational engineering.

Adjoint Based, Error Controlled, Loosely Coupled, Unstructured Design Optimization and Adaptive Mesh Refinement Using FUN3D

Adjoint Based, Error Controlled, Loosely Coupled, Unstructured Design Optimization and Adaptive Mesh Refinement Using FUN3D
Author: Troy E. Lake
Publisher:
Total Pages: 77
Release: 2017
Genre: Adjoint differential equations
ISBN: 9780355322934

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Adjoint-based design problems are dependent on the sensitivities from the CFD solution. Current best practices for these adjoint based design problems use fixed-complexity computational meshes that are built using developed best practices. An issue with these fixed-complexity computational meshes is that flow features may not be properly or completely captured. To improve the accuracy of the solution and the sensitivities, the mesh can be adaptively refined to reduce the discretization error within the flow solution. By adapting the mesh, the size of the mesh may be reduced as well, increasing the computational efficiency of the design problem. The computational efficiency of the design problem may also be improved with the use of progressive design variable parameterization. This research focuses on developing methodologies for variations of current best practices methods for design optimization problems including the use of adaptive mesh refinement and progressive design variable parametrization.

Adaptive Mesh Strategies for the Spectral Element Method

Adaptive Mesh Strategies for the Spectral Element Method
Author: Institute for Computer Applications in Science and Engineering
Publisher:
Total Pages: 28
Release: 1992
Genre:
ISBN:

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An adaptive spectral element method has been developed for the efficient solution of time dependent partial differential equations. Adaptive mesh strategies that include resolution refinement and coarsening by three different methods are illustrated on solutions to the one-dimensional viscous Burgers equation and the two-dimensional Navier-Stokes equations for driven flow in a cavity. Sharp gradients, singularities and regions of poor resolution are resolved optimally as they develop in time using error estimators which indicate the choice of refinement to be used. The adaptive formulation presents significant increases in efficiency, flexibility and general capabilities for high order spectral methods.

An Adaptive Mesh Refinement Technique for Dynamics of Solids

An Adaptive Mesh Refinement Technique for Dynamics of Solids
Author: Abhishek Trivedi
Publisher:
Total Pages: 154
Release: 2007
Genre:
ISBN:

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Simulation of dynamics problems generally is heavily dependent on mesh size for convergence and accuracy. In many cases, the requirement of mesh size reaches to such proportions that the problem becomes unsolvable for the available computational resources. We perceive that such problems can be solved by refining and unrefining mesh adaptively during time stepping. Adaptive mesh refinement techniques available in popular literature are marred by various limitations, such as element-specific techniques, algorithm-specific techniques, etc. We utilize Conforming Hierarchical Refinement Methods (CHARMS) [32] for our purpose since it relies on the refinement of finite element basis instead of geometric sub-division of elements. Refinement in this fashion produces conforming meshes during adaptive mesh refinement for a wide range of elements. We improve CHARMS to incorporate time stepping problems. In order to show the effectiveness of such an algorithm, we modify an explicit Newmark solver to incorporate it within the adaptive mesh refinement framework. We perform the analysis of conservation properties of the modified algorithm to understand its limitations. Later, we demonstrate application of such development with a very practical example, simulation of an NDE experiment using ultrasonic guided waves. Details presented in [76] has shown that such a simulation would otherwise not have been possible. We further study the guided wave experiment and optimize various parameters of the algorithm to validate experimental results.