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C-SAFE 2005 Image Gallery (Click thumbnail for larger view) Overarching Complete End to End Simulation These images depict the a complete end to end simulation run by the University of Utah's Center for the Simulation of Accidental Fires and Explosions (C-SAFE). Visualized is a sectional view of the rupturing of a steel container that is filled with a plastic bonded explosive and heated by a fire. The structural response of the container and the solid explosive is modeled using the Material Point Method (MPM). The fire and products of reaction of the explosive are modeled using a multi-material version of the Implicit Compressible Eulerian (ICE) CFD algorithm. This highly coupled multi-physics integrated simulation consists of three phases, all run by a single program. The first phase is the simulation of the fire, which runs for a period of time sufficient to compute a spatially resolved, time averaged rate of heat transfer to the container. Using this heat transfer rate, the simulation switches to the second phase (the heat up phase). During the heat up phase, the heat generated by the fire is absorbed by the container and transferred to the explosive. This phase of the simulation lasts on the order of tens of minutes. When the explosive temperature reaches approximately 450 degrees kelvin, it begins to react, rapidly pressurizing the container. At this point, the simulation switches to the third phase (the explosion phase). The explosion phase lasts several milliseconds. The simulation terminates when fragments of the cylinder escape the computational domain. The final result of the simulation, as depicted here, was calculated using 146 hours of computation time on 600 processors utilizing both the ALC and Thunder computers at Lawrence Livermore National Lab. The data from 200 time steps of this simulation, including the 2.8 million particles per time step, was visualized interactively using the Real Time Ray Tracer (RTRT) on 60 processors of an SGI Origin 3800. The particles are colored based on temperature; particle size corresponds to particle mass.
SCIRun Desktop Visualizations These visualizations were created using the SCIRun PSE software and depict the end of the end to end simulation. An isosurface (of mass) is used to display both the metal container, and the explosive. The fire and pressurized gas inside the container are rendered using SCIRun's volume visualization components.
Hollow Bore Explosive Simulation The first 5 of these images, rendered using SCIRun, show a time sequence of a container filled with an explosive containing a hollow core. The explosive collapses into the bore, exposing more surface area of the explosive and causing a larger reaction and thus a more violent explosion. The last image shows the result of a simulation in which the explosive completely fills the container.
Fire/Flare/Helium Plume Simulations Our simulations of helium plumes have shown the presence of Rayleigh-Taylor instabilities and the large votical structures they generate, an observation also made in helium plume experiments conducted at the Sandia-Albuquerque FLAME facility. These instabilities, also called bubbles and spikes, result when a heavy layer (air) sits over a light layer (helium) and lead to strong mixing. We have used the results of these simulations to better understand how vorticity is generated and to validate the accuracy of our CFD code. Industrial flares are used to vent and burn waste gases from oil and gas drilling and refining operations. The efficiency of burnout decreases in high wind conditions, which can affect air quality downstream of the flare. These simulations are some of the first in the world to show the time-dependent characteristics of such flows and to accurately model the changes that occur in the flow as a result of wind conditions. Of particular interest is the vortex shedding that can be see downstream of the flare stack. These flare simulations were run on the Frost machine at LLNL.
Visualization Techniques
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