THE BUNCEFIELD EXPLOSION: VAPOUR CLOUD DISPERSION AND OTHER OBSERVATIONS

A large scale computational fluid dynamic vapour dispersion model of the release in the Buncefield incident was constructed for the western half of the accident site. The area encompassed the carparks, the Northgate, Fuji, RO and 3-Com buildings, as well as half of the first row of western storage tanks within Bund A along Buncefield Lane. Time dependent comparisons over the known period of the release of the computed -0.1 degrees C and LFL CFD isosurfaces were made to several of the CCTV records of the developing event. The isosurface cloud extents appear to match reasonably the observed temporal and geometric developments as well as the vegetative singeing - indicative of the LFL boundary. Vehicles within the cloud, located at the cloud's western lean extremities, between the Fuji and Northgate Buildings as well as between the Northgate and 3-Com/RO Buildings, provide evidence of interior explosions prior to detonative-like crushing. Vehicles other than these appear to have been moved east by blast. Reasons for this are advanced. Several tanks, within the tank-farm, failed by dynamic elastic crushing caused by under sudden applied radial pulse loads. These failures are also examined. In instances where the roofs were torn off some simples analysis allows estimates of the necessary internal pressures and thus required blast exposures. These results appear to confirm earlier work undertaken of the necessary external pressures to move and deform vehicles in carparks and as well as debead and deflate some of their tyres. Finite Element blast analyses applied to some of the lampposts also suggest that the blast loadings were detonative.