Calculate the blast overpressure created by vapor cloud explosions with the U.S. Army and HSE TNT Equivalency, TNO Multi-Energy, and Baker-Strehlow-Tang (B-S-T) models. Scenario parameters can be incorporated into these models including proximity to ground level (ground reflection), density of obstacles, and vapor cloud flame speed. Incident Analyst’s explosion models make the conservative assumption of not modeling shielding from any specific structures. For more advanced explosion modeling capability, including shielding and calculation of damage to structures and people, BREEZE offers the powerful BREEZE Explosion Damage & Injury Assessment Model (ExDAM).
TNT Equivalency Models
For situations in which limited characteristics of an explosive vapor cloud are known, or in which a conservative estimate of blast effects is desired, the TNT equivalency models developed by the U.S. Army and U.K. Health and Safety Executive provide an excellent modeling option.
U.S. Army TNT Equivalency uses a proportional relationship between the flammable mass in the cloud and an equivalent weight of TNT, and assumes the entire flammable mass is involved in the explosion and is centered at a single location.
U.K. HSE TNT Equivalency uses a proportional relationship between the flammable mass in the cloud and an equivalent weight of TNT.
TNO Multi-Energy Model
An additional level of refinement in explosion modeling is provided by the TNO multi-energy model. This tool allows vapor cloud explosions to be better characterized with the definition of one or more sub-clouds.
The Baker-Strehlow-Tang model provides a powerful tool for simulating vapor cloud explosions that accounts for the degree of confinement (a key factor in determining whether a flash fire or a true explosion will occur), flame speed, ground reflection, and the number of directions in which the blast can expand. Like the TNO multi-energy model, the Baker-Strehlow-Tang model also allows an explosive vapor cloud to be characterized as multiple sub-clouds.