235 research outputs found
Achieving Extreme Resolution in Numerical Cosmology Using Adaptive Mesh Refinement: Resolving Primordial Star Formation
As an entry for the 2001 Gordon Bell Award in the "special" category, we
describe our 3-d, hybrid, adaptive mesh refinement (AMR) code, Enzo, designed
for high-resolution, multiphysics, cosmological structure formation
simulations. Our parallel implementation places no limit on the depth or
complexity of the adaptive grid hierarchy, allowing us to achieve unprecedented
spatial and temporal dynamic range. We report on a simulation of primordial
star formation which develops over 8000 subgrids at 34 levels of refinement to
achieve a local refinement of a factor of 10^12 in space and time. This allows
us to resolve the properties of the first stars which form in the universe
assuming standard physics and a standard cosmological model. Achieving extreme
resolution requires the use of 128-bit extended precision arithmetic (EPA) to
accurately specify the subgrid positions. We describe our EPA AMR
implementation on the IBM SP2 Blue Horizon system at the San Diego
Supercomputer Center.Comment: 23 pages, 5 figures. Peer reviewed technical paper accepted to the
proceedings of Supercomputing 2001. This entry was a Gordon Bell Prize
finalist. For more information visit http://www.TomAbel.com/GB
A low-numerical dissipation, patch-based adaptive-mesh-refinement method for large-eddy simulation of compressible flows
This paper describes a hybrid finite-difference method for the large-eddy simulation of compressible flows with low-numerical dissipation and structured adaptive mesh refinement (SAMR). A conservative flux-based approach is described with an explicit centered scheme used in turbulent flow regions while a weighted essentially non-oscillatory (WENO) scheme is employed to capture shocks. Three-dimensional numerical simulations of a Richtmyer-Meshkov instability are presented
Scalable Adaptive Mantle Convection Simulation on Petascale Supercomputers
Mantle convection is the principal control on
the thermal and geological evolution of the Earth. Mantle
convection modeling involves solution of the mass, momentum,
and energy equations for a viscous, creeping, incompressible
non-Newtonian fluid at high Rayleigh and Peclet
numbers. Our goal is to conduct global mantle convection
simulations that can resolve faulted plate boundaries, down
to 1 km scales. However, uniform resolution at these scales
would result in meshes with a trillion elements, which
would elude even sustained petaflops supercomputers. Thus
parallel adaptive mesh refinement and coarsening (AMR)
is essential.
We present RHEA, a new generation mantle convection
code designed to scale to hundreds of thousands of cores.
RHEA is built on ALPS, a parallel octree-based adaptive
mesh finite element library that provides new distributed
data structures and parallel algorithms for dynamic coarsening,
refinement, rebalancing, and repartitioning of the
mesh. ALPS currently supports low order continuous
Lagrange elements, and arbitrary order discontinuous
Galerkin spectral elements, on octree meshes. A forest-ofoctrees
implementation permits nearly arbitrary geometries
to be accommodated. Using TACC’s 579 teraflops
Ranger supercomputer, we demonstrate excellent weak and
strong scalability of parallel AMR on up to 62,464 cores
for problems with up to 12.4 billion elements. With RHEA’s
adaptive capabilities, we have been able to reduce the
number of elements by over three orders of magnitude,
thus enabling us to simulate large-scale mantle convection
with finest local resolution of 1.5 km
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