Non-Spherical Blast in a Cluttered Environment

Physics-based computational solutions facilitate the understanding of the behavior of structures subjected to high-explosives. However, design and parameter studies remain costly, because computational fluid mechanics models of blast waves may require supercomputers. On the other hand, extremely efficient approximate models of blast loading fail to resolve the effects of interest: close-proximity blast, non-spherical charges, complex geometry, motion of the charge, reflections and shadowing in a cluttered environment. The proposed approach combines the efficiency of approximate blast loading models with resolution of the required effects. Since commercially available explicit Lagrangian finite element software technology is almost always used to analyze structures exposed to blast loading, our module will be implemented using such a code. Weidlinger has already demonstrated software for close-in charges which synthesizes pressure distributions using stored, pre-computed CFD solutions. CFD is not performed at runtime. The proposed module will blend established empirical formulae and the synthesized, CFD-based pressure functions. Charge motion will be accounted for by linear Doppler theory. Reflections will be handled using ray-tracing for general surfaces defined in terms of finite element geometry, computing lines of sight, interaction distances and occlusion for facets in the surface. The module will be validated against experimental data. BENEFITS: The modular blast software technology proposed here will deliver numerous direct and indirect commercial benefits. The immediate commercial application will be to the simulation of blast effects on airframe structures of interest to the Air Force, and to ground targets. The advantages of a high-resolution pure-Lagrangian approach in these applications are considerable. By avoiding computational fluid dynamics or other computer-intensive methods, the analyst can concentrate on the aircraft or ground structure of interest and explore many more cases for the same expenditure of resources. The modular design of the proposed blast loading module(s) allows WAI to access the large existing markets consisting of users of LS-DYNA, Abaqus, and DYTRAN, as well as Weidlingers NLFlex and EPSA codes.