1,954 research outputs found
Block Structured Adaptive Mesh and Time Refinement for Hybrid, Hyperbolic + N-body Systems
We present a new numerical algorithm for the solution of coupled collisional
and collisionless systems, based on the block structured adaptive mesh and time
refinement strategy (AMR). We describe the issues associated with the
discretization of the system equations and the synchronization of the numerical
solution on the hierarchy of grid levels. We implement a code based on a higher
order, conservative and directionally unsplit Godunov's method for
hydrodynamics; a symmetric, time centered modified symplectic scheme for
collisionless component; and a multilevel, multigrid relaxation algorithm for
the elliptic equation coupling the two components. Numerical results that
illustrate the accuracy of the code and the relative merit of various
implemented schemes are also presented.Comment: 40 pages, 10 figures, JPC in press. Extended the code test section,
new convergence tests, several typos corrected. Full resolution version
available at http://www.exp-astro.phys.ethz.ch/miniati/charm.pd
GRChombo : Numerical Relativity with Adaptive Mesh Refinement
In this work, we introduce GRChombo: a new numerical relativity code which
incorporates full adaptive mesh refinement (AMR) using block structured
Berger-Rigoutsos grid generation. The code supports non-trivial
"many-boxes-in-many-boxes" mesh hierarchies and massive parallelism through the
Message Passing Interface (MPI). GRChombo evolves the Einstein equation using
the standard BSSN formalism, with an option to turn on CCZ4 constraint damping
if required. The AMR capability permits the study of a range of new physics
which has previously been computationally infeasible in a full 3+1 setting,
whilst also significantly simplifying the process of setting up the mesh for
these problems. We show that GRChombo can stably and accurately evolve standard
spacetimes such as binary black hole mergers and scalar collapses into black
holes, demonstrate the performance characteristics of our code, and discuss
various physics problems which stand to benefit from the AMR technique.Comment: 48 pages, 24 figure
Emerging CFD technologies and aerospace vehicle design
With the recent focus on the needs of design and applications CFD, research groups have begun to address the traditional bottlenecks of grid generation and surface modeling. Now, a host of emerging technologies promise to shortcut or dramatically simplify the simulation process. This paper discusses the current status of these emerging technologies. It will argue that some tools are already available which can have positive impact on portions of the design cycle. However, in most cases, these tools need to be integrated into specific engineering systems and process cycles to be used effectively. The rapidly maturing status of unstructured and Cartesian approaches for inviscid simulations makes suggests the possibility of highly automated Euler-boundary layer simulations with application to loads estimation and even preliminary design. Similarly, technology is available to link block structured mesh generation algorithms with topology libraries to avoid tedious re-meshing of topologically similar configurations. Work in algorithmic based auto-blocking suggests that domain decomposition and point placement operations in multi-block mesh generation may be properly posed as problems in Computational Geometry, and following this approach may lead to robust algorithmic processes for automatic mesh generation
ICASE/LaRC Workshop on Adaptive Grid Methods
Solution-adaptive grid techniques are essential to the attainment of practical, user friendly, computational fluid dynamics (CFD) applications. In this three-day workshop, experts gathered together to describe state-of-the-art methods in solution-adaptive grid refinement, analysis, and implementation; to assess the current practice; and to discuss future needs and directions for research. This was accomplished through a series of invited and contributed papers. The workshop focused on a set of two-dimensional test cases designed by the organizers to aid in assessing the current state of development of adaptive grid technology. In addition, a panel of experts from universities, industry, and government research laboratories discussed their views of needs and future directions in this field
Grid generation for the solution of partial differential equations
A general survey of grid generators is presented with a concern for understanding why grids are necessary, how they are applied, and how they are generated. After an examination of the need for meshes, the overall applications setting is established with a categorization of the various connectivity patterns. This is split between structured grids and unstructured meshes. Altogether, the categorization establishes the foundation upon which grid generation techniques are developed. The two primary categories are algebraic techniques and partial differential equation techniques. These are each split into basic parts, and accordingly are individually examined in some detail. In the process, the interrelations between the various parts are accented. From the established background in the primary techniques, consideration is shifted to the topic of interactive grid generation and then to adaptive meshes. The setting for adaptivity is established with a suitable means to monitor severe solution behavior. Adaptive grids are considered first and are followed by adaptive triangular meshes. Then the consideration shifts to the temporal coupling between grid generators and PDE-solvers. To conclude, a reflection upon the discussion, herein, is given
A survey of high level frameworks in block-structured adaptive mesh refinement packages
pre-printOver the last decade block-structured adaptive mesh refinement (SAMR) has found increasing use in large, publicly available codes and frameworks. SAMR frameworks have evolved along different paths. Some have stayed focused on specific domain areas, others have pursued a more general functionality, providing the building blocks for a larger variety of applications. In this survey paper we examine a representative set of SAMR packages and SAMR-based codes that have been in existence for half a decade or more, have a reasonably sized and active user base outside of their home institutions, and are publicly available. The set consists of a mix of SAMR packages and application codes that cover a broad range of scientific domains. We look at their high-level frameworks, their design trade-offs and their approach to dealing with the advent of radical changes in hardware architecture. The codes included in this survey are BoxLib, Cactus, Chombo, Enzo, FLASH, and Uintah
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