Doctor of Philosophy

dissertationThe detonation of hundreds of explosive devices from either a transportation or storage accident is an extremely dangerous event. Motivation for this work came from a transportation accident where a truck carrying 16,000 kg of seismic boosters overturned, caught fire and detonated. The damage was catastrophic, creating a crater 24 m wide by 10 m deep in the middle of the highway. Our particular interest is understanding the fundamental physical mechanisms by which convective deflagration of cylindrical PBX-9501 devices can transition to a fully-developed detonation in transportation and storage accidents. Predictive computer simulations of large-scale deflagrations and detonations are dependent on the availability of robust reaction models embedded in a computational framework capable of running on massively parallel computer architectures. Our research group has been developing such models in the Uintah Computational Framework, which is capable of scaling up to 512 K cores. The current Deflagration to Detonation Transition (DDT) model merges a combustion model from Ward, Son, and Brewster that captures the effects of pressure and initial temperature on the burn rate, with a criteria model for burning in cracks of damaged explosives from Berghout et al., and a detonation model from Souers describing fully developed detonation. The prior extensive validation against experimental tests was extended to a wide range of temporal and spatial scales. We made changes to the reactant equation of state-enabling predictions of combustions, explosions, and detonations over a range of pressures spanning five orders of magnitude. A resolution dependence was eliminated from the reaction model facilitating large scale simulations to be run at a resolution of 2 mm without loss of fidelity. Adjustments were also made to slow down the flame propagation of conductive and convective deflagration. Large two- and three-dimensional simulations revealed two dominant mechanisms for the initiation of a DDT, inertial confinement and Impact to Detonation Transition. Understanding these mechanisms led to identifying ways to package and store explosive devices that reduced the probability of a detonation. We determined that the arrangement of the explosive cylinders and the number of devices packed in a box greatly affected the propensity to transition to a detonation

Multiscale modeling of accidental explosions and detonations

pre-printAccidental explosions are exceptionally dangerous and costly, both in lives and money. Regarding worldwide conflict with small arms and light weapons, the Small Arms Survey has recorded more than 297 accidental explosions in munitions depots across the world that have resulted in thousands of deaths and billions of dollars in damage in the past decade alone.1 As the recent fertilizer plant explosion that killed 15 people in the town of West, Texas demonstrates, accidental explosions aren't limited to military operations. Transportation accidents also pose risks, as illustrated by the occasional train derailment/explosion in the nightly news, or the semi-truck explosion detailed in the following section. Unlike other industrial accident scenarios, explosions can easily affect the general public, a dramatic example being the Pacific Engineering and Production Company of Nevada (PEPCON) plant disaster in 1988, where windows were shattered, doors were blown off their hinges, and flying glass and debris caused injuries up to 10 miles away

Parallel Scientific Computing with Applications in Material Science and Metallurgy

A new software tool for the solution of complex time-dependent systems of partial differential is presented. High levels of parallelization are achieved in a framework that allows the developer to implement ad-hoc solvers for computationally challenging problems on a higher abstraction level without the need to understand in the low-level parallel implementation. Moreover, thanks to this new implementation, advanced numerical methods, such as mesh adaptivity, implicit time stepping, and multigrid methods can be employed with ease. Here the implementation of this new tool is presented and validated against simple elliptic and more complex phase-field models. Its parallel performance is then assessed