An application of the Hudson clearing method to near-field blast loading and above-ground explosions

Clearing effects influence the pressure-time history experienced by surface structures of finite size. This is a phenomenon that results in gradually reducing the reflected pressures on the front face of a building, to the lower free-field pressures experienced by the sides and roof. The Hudson method is a first-principles approach to account for clearing effects on finite surface structures by superimposing the reflected pressures derived on infinite surfaces with pressure relief waveforms travelling from the free edges. This method has shown good agreement with experimental and numerical results in the mid- and far-field, when a single Friedlander blast wave is assumed to impinge on a surface. This paper will explore the application of the Hudson clearing method to above-ground explosions with targets located above the triple-point path, where the pulse consists of two Friedlander blast waves, resulting from the incident and ground-reflected waves arriving separately at the target. Furthermore, the limitations of the Hudson clearing method to near-field explosions will also be assessed. For both cases, the semi-empirical Low Altitude Multiple Burst (LAMB) addition method will be considered in the derivation of the reflected pressure-time histories on infinite surfaces. To assess the predictions of the Hudson clearing method, these will be compared with the results from computational fluid dynamic analyses.