SimEx: A Tool for the Rapid Evaluation of the Effects of Explosions

Abstract

The dynamic response of structural elements subjected to blast loading is a problem of growing interest in the field of defense and security. In this work, a novel computational tool for the rapid evaluation of the effects of explosions, hereafter referred to as SimEx, is presented and discussed. The classical correlations for the reference chemical (1 kg of TNT) and nuclear (106 kg of TNT) explosions, both spherical and hemispherical, are used together with the blast wave scaling laws and the International Standard Atmosphere (ISA) to compute the dynamic response of Single-Degree-of-Freedom (SDOF) systems subject to blast loading. The underlying simplifications in the analysis of the structural response follow the directives established by UFC 3-340-02 and the Protective Design Center Technical Reports of the US Army Corps of Engineers. This offers useful estimates with a low computational cost that enable in particular the computation of damage diagrams in the Charge Weight–Standoff distance (CW–S) space for the rapid screening of component (or building) damage levels. SimEx is a computer application based on Matlab and developed by the Fluid Mechanics Research Group at University Carlos III of Madrid (UC3M). It has been successfully used for both teaching and research purposes in the Degree in Security Engineering, taught to the future Guardia Civil officers at the Spanish University Center of the Civil Guard (CUGC). This dual use has allowed the development of the application well beyond its initial objective, testing on one hand the implemented capacities by undergraduate cadets with the end-user profile, and implementing new functionalities and utilities by Masters and PhD students. With this experience, the application has been continuously growing since its initial inception in 2014 both at a visual and a functional level, including new effects in the propagation of the blast waves, such as clearing and confinement, and incorporating new calculation assistants, such as those for the thermochemical analysis of explosive mixtures; crater formation; fragment mass distributions, ejection speeds and ballistic trajectories; and the statistical evaluation of damage to people due to overpressure, body projection, and fragment injuries.

Linear Theory of Hypersonic Shocks Interacting with Turbulence in Air

“…There is a fourth closed-source (i.e., proprietary) module, CT-EXPLO, that estimates the theoretical properties of high explosive mixtures and multi-component propellants with non-ideal EoS. Although still under development, CT-EXPLO is distributed in its current form as the thermochemical module of SimEx [152] subject to a proprietary license. Further details on this module will be provided elsewhere.…”

“…The validation with other codes is performed in the following subsection in the context of oblique detonations. However, for detonation velocities related to condensed-phase explosives, we refer to SimEx [152] propellants and explosives, and its kernel from CT was adapted to solve the products' composition with the ideal gas EoS following the norm UNE 31-002-94 [183]. SimEx also employs more complex computations based on the European Standard EN 13631-15 [184], which use the semi-empirical Becker-Kistiakowsky-Wilson (BKW) [31,185] or the Heuzé (H9) EoS [186].…”

“…This MATLAB-GUI thermochemical code represents the core of an ongoing research work the has been used to investigate a series of problems during the last few years (see Chapters 3 to 5 and Ref. [152]). Results are in excellent agreement with NASA's CEA code [10], Cantera [41] within Caltech's Shock and Detonation Toolbox (SD-Toolbox) [40,118], and the recent Thermochemical Equilibrium Abundances (TEA) code [18].…”