DIELECTRIC-BREAKDOWN IN A SIMPLIFIED PARALLEL MODEL

The growth of streamer trees in insulating fluids (a submicrosecond pr ocess that triggers high-voltage breakdown) has been simulated with a combination of parallel-coding tools. Large grids and arrays display w ell the multifractal, self-avoiding character of the streamer trees. T hree physical cases have been approximated by different power-law weig htings of the statistical growth filter: dense anode trees, in the uni form field; sparse cathode trees (a rarer experimental case); and ultr asparse anode trees (seen in some fluids of higher viscosity). The mod el is contained in a software package that is written in Fortran 90 wi th data parallel extensions for distributed execution. These extension s encapsulate an underlying, invisible message-passing environment, th us enabling the solution of memory-intensive problems on a group of li mited-memory processors. Block partitioning creates processes of reaso nable size, which operate in parallel like small copies of the origina l code. The user needs only to express his model in transparent array- directed commands; parallel interfacing between blocks is handled invi sibly. Breakdown is performed in parallel in each of the local blocks. Results are presented for experiments run on eight and nine nodes of the IBM SP2. and four and eight nodes of the SGI Onyx and Origin, thre e examples of multiple-processor machines. Display is carried out in t hree dimensions. Timing of the growth can be shown by color banding or by frame animation of the results. The adequacy of the growth rules a nd size scaling are tested by comparing the simulations against snapsh ots from high-voltage discharge events.