MicroBlast: The influence of obstacle orientation on the variability of blast loading in urban environments

Explosions in urban environments, whether deliberate or accidental, are a significant threat to the modern world. The presence of obstacles and reflecting surfaces results in the coalescence of multiple blast wave fronts, leading to highly complex loading profiles that differ significantly from those in free air. Currently, predicting the loads in these domains requires numerical modelling tools that cannot rapidly evaluate the risk posed to a given environment in a probabilistic manner. To achieve this, new methods will need to be developed with an understanding of the most important parameters that dictate loading throughout an urban space. Previous studies have worked towards this goal by exploring the influence of various global geometric parameters including areal density, street width, and building height. However, the role of local obstacle orientation is yet to be explored. By simulating 50 unique layouts, with an experimentally validated solver, that maintain a consistent areal density and obstacle spacing, it is shown that the peak overpressure is largely dictated by two factors: the shortest path of the blast wave to the point of interest, and the orientation/proximity of the reflecting surfaces in the immediate surroundings. This differs from the peak specific impulse that is instead likely to be controlled by global parameters, possibly including the areal density and an approximate travel distance from the charge that represents the flow of the energy from the charge.