Simplified blast loading for internal explosions using spherical, cylindrical and planar blast

For the simulation of blast loading on walls resulting from an internal explosion in a simplified approach, this study presents an improvement based on the use of so-called mirror charges. The improvement consists of using either Spherical, Cylindrical or Planar (SCP) blast waves (or a combination of them) instead to only spherical blast waves. If one considers, for example, an explosion occurring at one end of a long corridor, the blast propagation along the corridor resembles that of a planar blast (expansion in one direction only). Using spherical blast waves of the mirror charges are not able to preserve the strength of the blast front for such a scenario, resulting in a significant lack of accuracy for the loading on the walls. The SCP method makes use of planar blast waves in such a scenario, therefore preserving the strength of the blast front. Cylindrical blast waves are used, for example, in room with wide and long compartments compared to the room height. This study presents quantitatively the improvement of using the SCP method based on both the blast loading and the response of a realistic bulkhead for a ship compartment. In order to cover as many realistic scenarios as possible, four different room aspect ratios are considered with different charge locations for a total of 12 different scenarios. Based on the bulkhead displacement, it is shown that the error made by using only spherical blast waves can be as much as ±50%, especially for long and narrow compartments, compared to a detailed CFD (Computational Fluid Dynamics) analyses. Using the SCP method, the inaccuracies are reduced by two to threefold depending on the compartment geometry. Although the SCP approach is applied in this study to ship compartments, it can also be used for a wider range of applications involving internal explosions.