Preliminary numerical evaluation of clearing effects in the near-field

For finite-sized targets subjected to a blast wave from an explosive event, the presence of an edge results in the generation of a clearing wave that moves inwards from the edge of the panel and acts to relieve the pressure on the target. Whilst previous investigations have focused on the role of clearing for far-field blast loading scenarios, minimal work has been documented within the near-field. This numerical investigation focuses on quantifying the role of clearing on the impulse delivered to different sized targets for both near-field and far-field scenarios. The spatial distribution of loading is quantified using the flying ring technique, which enables the influence of clearing to be evaluated for a range of target sizes. Initial studies simulated a 1 kg spherical C4 charge, with the stand-off distance adjusted to evaluate the influence of clearing at a range of scaled distances. The results indicated that while clearing has a more pronounced effect for larger stand-off distances; it was still found to provide a significant reduction in momentum for small targets (< 0.25 m radius) at scaled distances of 0.5 m/kg1/3. An assessment of the influence of clearing indicated that the results for different loading conditions could be simplified by defining a normalized target radius (target radius / stand-off distance). The findings of this study can be used to inform designers of the scenarios where clearing should be taken into account.