Misuse of Simple Explosion Tools in Complex Explosion Investigations
Scott Davis, Ph.D., P.E., CFEI
Derek Engel, CFEI
Peter Hinze, Ph.D., P.E., CFEI
GexCon US, U.S.A.
Presented at the International Symposium on Fire Investigation Science and Technology, 2014
There are numerous simple models that can be used to assist the investigation into fuel-air explosions. These models include simple equilibrium based unvented explosions, single and multiple vent equations for large vessels and rooms, constant flame speed models with completely unconfined and fixed congestion (e.g, TNO Multi-energy model, BST method), TNT equivalent models that compare explosion consequences for gas phase explosions with TNT, etc. Some of these simplified methods can help predict both the free-field blast pressure, as well as the dynamic effects due to the venting of the expanding cloud (e.g., drag forces resulting from the blast wind).
While these models may be appealing to assist in an investigation, extreme caution needs to be exercised when using these models outside their intended application. For example, asymmetries and non-uniform congestion, or partially confined structures can result in simple tools vastly over or under-predicting explosion loads and the associated dynamic effect. This data is oftentimes critical in an accident investigation. This paper will present a variety of case studies where simple tools were incorrectly applied to complex explosion investigations, resulting in incorrect opinions regarding the incident. In contrast, the paper will compare the simplified results with those obtained using more advanced CFD modeling.
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