Research Overview
Science-Driven Simulation
A large part of CCSE's effort is focused on the development and application
of computer simulations for complex fluid flow problems. The diverse range of scientific
applications that drive our research typically involve a large range
of spatial and temporal scales (e.g. turbulent reacting flows) and
often require the use of massively parallel HPC systems.
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Core Methodology
Our approach to these problems centers on the development and application of
advanced algorithms that exploit known separations in scale; for many
of our application areas this results in algorithms are several orders
of magnitude more efficient than traditional simulation approaches.
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Common features of many of our algorithms include:
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Beyond Simulation
In some science areas, the most important limiting factor in simulation fidelity
is now the uncertainty in the input parameters.
We are developing new methodolgy for using observational and experimental
data to improve simulation fidelity. Click
here
to learn more.
Another research area in CCSE is algorithm development for black-box
global optimization; click
here
to learn more.
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Current Application Areas
Fluctuating Hydrodynamics
At molecular scales, fluids are inherently noisy with thermally induced fluctuations playing a key role in the dynamics.
When mechanical instabilities, chemical reactions and other phenomena at the microscopic scale are sensitive to
these fluctuations, fluctuations can affect behavior at larger scales.
The goal of this project is to develop stochastic hybrid models and algorithms to simulate these types of multiscale problems
arising in fluids....[more]
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Low
Mach Number Modeling of Moist Atmospheric Flows
We have developed a low Mach number model for moist atmospheric
flows that accurately incorporates reversible moist processes
in flows whose features of interest occur on advective rather
than acoustic time scales.
This 3-d cloud was simulated using the new low Mach number approach, implemented in a variant of the
MAESTRO code.
Iso-contours of liquid water are depicted, intersected by a vertical plane where
the concentration of water vapor is indicated.
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Laboratory-Scale Flames
Numerical simulation of laboratory-scale combustion devices
has the potential to close the gap between theory and experiment and
to enable dramatic progress in combustion
science. However, simulation of practical-scale combustion devices is
an immense undertaking. The problem is inherently multi-scale both in
time and space, the fuel is often turbulent, and the combustion
process may involve hundreds of species and thousands of chemical
reactions. The work here focuses in particular on numerical simulations
that are to be compared directly with experimental
diagnostics...[more]
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Premixed Hydrogen Flames
Advanced ultra-low-emissions burner devices will burn complex mixtures of
hydrocarbon and hydrogen fuels arising from various gasification processes (coal, biomass, ...).
These fuels burn in extremely
complex modes that are not amenable to traditional combustion modeling approaches.
We have developed a unique capability for long-time detailed simulation of such systems
and are using it to explore flame stability and propagation characteristics. We are
looking in particular at how such flames are affected by turbulent forcing across a
broad range of length and time scales, from freely-propagating cellular burning modes
to fully-distributed (highly turbulent) combustion....[more].
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Porous Media
The Department of Energy is responsible for clean-up and management of Cold War production
facilities and for monitoring contaminant behavior in groundwater around waste disposal
and storage areas.
High-fidelity simulations of groundwater flow have the potential for providing valuable insights into
long-term fate of contaminants; however, realizing this potential presents significant computational
challenges. The goal of this project is to develop an adaptive mesh framework for solving multiphase, reactive
transport in the subsurface...[more]
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Low Mach Number Astrophysics
Type Ia supernovae are the largest thermonuclear explosions in the universe, but
the exact mechanism of their demise is still a mystery.
Using MAESTRO, a new low Mach number astrophysics code
developed by CCSE in collaboration with Mike Zingale of Stony Brook University,
we have performed the first 3D full-star simulations of convection in a white dwarf
leading up to the ignition of a Type Ia supernova...[more]
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Compressible Astrophysics
As part of the SciDAC Computational Astrophysics Consortium, CCSE, in collaboration with
Louis Howell
at LLNL, have developed CASTRO, a new multi-dimensional Eulerian AMR
radiation-hydrodynamics code that includes stellar equations of state, nuclear reaction
networks, and self-gravity. Initial target applications for CASTRO include
Type Ia and Type II supernovae...[more]
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Nuclear Flames
Flame ignition in Type Ia supernovae (SNe Ia) leads to isolated bubbles of burning buoyant fluid.
As a bubble rises due to gravity, it becomes deformed by shear instabilities and transitions to turbulent
evolution.
The image on the left is a three-dimensional rendering of a snapshot of the burning case.
The burning rate is shown in orange, and the vorticity is shown in blue....[more]
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Incompressible Flow
Modeling of incompressible and low-speed flows has become one of the cornerstones
of the simulation capability of CCSE. This capability has been the springboard for CCSE's combustion
modeling capability, as well as useful in itself for explorations of
incompressible, nonreacting turbulent flow, as shown ...[more]
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