CAP Phase II Simulations for the Air Force HEL-JTO Project: Atmospheric Turbulence Simulations on NAVO´s 3000-Processor IBM P4+ and ARL´s 2000-Processor Intel Xeon EM64T Cluster

Shear turbulence induced by the Kelvin-Helmholtz (KH) instability in a stratified fluid is simulated in support of the Air Force High-Energy-Laser Joint Tactical Office (HEL-JTO) project using the new 3000-processor NAVO IBM Power 4+ system (Kraken). The results are used to 1) compare with and improve a dynamic LES method we have developed, and 2) provide the high-resolution simulation component of a new subgrid-scale (SGS) model we have developed for optical turbulence forecasting. We also discuss the relative performance of Kraken and the new 2000-processor Intel XEON EM64T cluster (Jvn) at ARL, pointing out differences which amount primarily to inter-node network performance. We suggest "%of wall time spent communicating" as a standard DoD benchmark criterion for very large distributed systems, as other more conventional criteria do not necessarily represent this important system and algorithm metric.