Non Ideal Airblast Effects from Urban and Natural Terrain

Joe Crepeau, Charles Needham, ARA

Abstract:
Non-ideal airblast is produced from detonations over urban and natural terrain. Mechanical effects of a blast wave reflecting off non-ideal surfaces produces shielding and channeling effects that may be considerably different than those from a detonation over an ideal surface. Work in the area non-ideal airblast generated from urban and natural terrain is presented.

Divine Strake is a high-explosive (HE) test sponsored by the Defense Threat Reduction Agency (DTRA) and is scheduled for the summer of 2006 at the Nevada Test Site (NTS). The test is a detonation of a 700 ton buried heavy AN/FO charge above a tunnel structure. The main purpose of the test is to study ground shock effects on deeply buried tunnel structures. Of secondary interest is the airblast produced by a buried charge and its modification as it propagates over the local terrain.

Sandia National Laboratory (SNL) recently sponsored a number of computational fluid dynamics (CFD) airblast calculations of the upcoming event. SNL contracted Applied Research Associates, Inc. (ARA) to perform two- and three-dimensional (2D and 3D) predictive airblast calculations for the test. The CFD calculations were run with SHAMRC and characterize the airblast environments induced by the non-ideal charge configuration and the surrounding terrain. They include 2D calculations with and without terrain and with a responding and non-responding ground model. A single 3D calculation with a non-responding ground model was also completed. Results of the calculations provide test planners with environments that can be expected at instrumentation and test structure locationS. A single, 3D calculation with a realistic ground model is planned once the charge and detonation site details are finalized.

ARA has also completed several SHAMRC calculations investigating non-ideal airblast over urban and natural terrain under a contract with DTRA for the Near Surface Weapons Effects Tools – 3D (NSWET-3D), Airblast/Thermal task. One set of calculations modeled a nuclear detonation in New York City. The buildings were generated automatically from ArcView shapefiles, placed on a flat ground surface, and modeled as non-responding. One of these calculations was run under the Capability Applications Project (CAP) sponsored by the Department of Defense (DoD) High Performance Computing Modernization Program (HPCMP). Another set of calculations modeled the Smoky nuclear event at NTS. The calculations included models of natural terrain, thermal heating of the terrain surface, and dust sweep-up from the surface.

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