Master's Thesis Proposal

Hruday Shah

Advisor: Dr. Suresh Menon

"High-Explosive Detonation-Driven Simulant Decomposition in Confined
Environments"

Monday, July 28

11:00 a.m. 

Montgomery Knight Building 317
270 Ferst Dr, Atlanta, GA 30332
 

Abstract
When high explosives (HE) detonate, a leading blast wave is formed and propagates outward. In
confined lab-scale geometries, before this wave can reflect off the walls, expansion pressure waves
generated behind the front will travel in the opposite direction and reflect from the initial source as a reshock.
This re-shock interacts with the evolving shear layers, enhancing post-detonation mixing, still
before the initial blast wave reflects. Shear-layer instabilities, particularly Kelvin–Helmholtz instability
(KHI) and Rayleigh–Taylor instability (RTI), are triggered by the velocity and density gradients in the flow,
and when perturbed by the re-shock, can give rise to Richtmyer–Meshkov instability (RMI). These
instabilities enhance mixing between detonation products and ambient gases. If a surrogate species is
introduced into the ambient domain, mixing and decomposition occur, independent of direct blast wave
interaction. However, the mixing and decomposition behavior of such simulants in confined postdetonation
geometries remains poorly understood, and limited numerical studies exist, due to the lack
of data, especially on simulant decomposition kinetics.

To address some of these gaps, this thesis proposes a numerical investigation of confined HE
detonations and modeling post-blast mixing and decomposition of simulant gas. The effects of varying
initial simulant conditions on mixing and decomposition will also be evaluated across both short- and
long-time scales. For the numerical modeling framework, a confined spherical blast is modeled using the
semi-empirical Jones-Wilkins-Lee (JWL) Equation of State and finite-rate reduced-order kinetics for
afterburning. If the simulant and ambient gases are turbulent, large-eddy-simulation (LES) will be used;
otherwise, no turbulent modeling will be used. This framework is verified against experimental data.
This numerical framework is then also applied to a lab-scale cylindrical chamber with a generic two-step
kinetics model for simulant decomposition. Initial simulations reveal that the simulant placement
significantly affects mixing rates, while geometry influences mean temperature. It is shown that the
mean simulant temperature is a key driver for decomposition. Additional configurations, based on
planned experiments at the University of Illinois, will be modeled to further verify and characterize
these findings.

Committee
* Dr. Suresh Menon – School of Aerospace Engineering
* Dr. Joseph Oefelein – School of Aerospace Engineering
* Dr. Lakshmi Sankar – School of Aerospace Engineering