October 2006
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Reconstruction Method Developed
A Sandia team (Stewart J. Mosso,Christopher J. Garasi, Richard R. Drake, and Allen C. Robinson) has developed and implemented a second-order accurate material interface reconstruction method in the ALEGRA High Energy Density Physics (HEDP) code. This method provides a higher fidelity approach for the simulation of material motion. The higher-order interface reconstruction algorithm is being applied to Rayleigh-Taylor unstable interfaces between conductive materials under rapid acceleration from very strong magnetic forces induced by large electrical currents. These interfaces are commonly encountered within simulations of experiments completed on Sandia’s Z machine. The simulation of material motion is particularly sensitive to the accuracy of the reconstruction method. Lower order methods produce more ejecta, which has a large effect on the material state, especially the compression/stagnation of the materials by magnetic forces.
The new method, called Patterned Interface Reconstruction (PIR), evolved from the Young’s Method (AWE) and the Stability Point ideas of Blair Swartz (LANL). This algorithm is a computationally efficient yet accurate method. A simple demonstration [375 KB] is the motion of a slab through a mesh, in which the PIR method reproduces the analytic result. A second demonstration 1.2 MB] is of a sphere moving through a mesh. In both demonstrations, as the material interface exits the mesh boundary, little or no distortion of the interface occurs. This is in contrast to the unsmoothed method in which mesh boundary effects show large distortions of the interfaces for both slab [366 KB] and sphere [1.2 MB].
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