Numerical investigation of blast loading from cube shape explosive charges

Accurate and rapid quantification of blast loading is essential to ensure infrastructure resilience against explosions. There is significant literature on the assessment of the blast output from (hemi-)spherical charges, and it is generally accepted that simplified empirical methods and high-fidelity numerical solvers can accurately quantify the loading from these charges. Many explosions, accidental or otherwise, are not the result of such idealised charge shapes, and therefore the associated loading may significantly differ from those predicted by modelling. This work investigates the accuracy of using the CFD code Viper Blast as a tool for modelling cube-shaped charges in the far field. The models are compared to well-controlled experimental data from previous work using 250g PE4 charges at a range of standoff distances. Cube charges are shown to exhibit a significant subsequent shock, equal in magnitude to the primary shock in some instances. It is shown that Viper Blast is able to model this behaviour with sufficient accuracy, however the results are highly mesh dependent and sensitive to the exact choice of equation of state parameters used to represent the explosive. The modelling work indicates that loading features which persist well into the far field are governed by complex early-stage processes which are not present in commensurate models with hemispherical charges. This highlights the need to accurately model detonation and immediate post-detonation behaviour in numerical simulations in order to represent far field blast loading of non-spherical explosive charges.