Modeling the Effects of Detonations of High Explosives to Inform Blast Resistant Design

Keywords: Blast-resistant designs.  Explosive charges.  Blast loads.  Finite element (FE) analyses.  LS-DYNA.  AUTODYN.  Computational fluid dynamics (CFD).  Air3D.  Fluid-structure interaction.  UFC-3-340.  Predictions.  Damage.  TNT.

Abstract: A comprehensive survey of different strategies to model detonations in commercially available finite element (FE) codes LS-DYNA and AUTODYN and the computational fluid dynamics (CFD) code Air3D was conducted.  A robust modeling strategy capable of modeling different charge shapes and fluid-structure interaction was identified is LS-DYNA and the use of remapping capabilities in AUTODYN and Air3D was demonstrated.  A near-field detonation of a spherical charge of TNT and the subsequent fluid-structure interaction with a rigid column was modeled using the three codes.  There were significant differences between the results of the FE and CFD analysis, and between these results and the predictions of UFC-3-340.  The reasons for the differences include the change in the value of constant specific heat ratio (gamma), of air at high temperatures, the effect of afterburning on the reflected impulse, and the effect of blast-wave clearing on both the reflected peak overpressure and impulse.