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.
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.
Current Application Areas
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]
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.
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]
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].
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]
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]
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]
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]
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]