(278c) Application of Computational Fluid Dynamics (CFD) to Boiling Liquid Expanding Vapor Explosions (BLEVEs)

A boiling-liquid expanding-vapor explosion (BLEVE) occurs when a vessel containing pressurized liquefied gas ruptures, resulting in the instantaneous release of the boiling liquid, vessel fragments, and blast wave. For structural design loading, the overpressure and impulse from a postulated BLEVE uses the method provided in Guidelines for Vapor Cloud Explosion, Pressure Vessel Burst, BLEVE and Flash Fire Hazard. The method’s conservative assumptions provide a bounding estimate for the overpressure and impulse that would most likely occur during any BLEVE.  However, using CFD to simulate a pressure vessel burst can provide a more realistic estimate of the blast wave where complex geometries exist.  Using the modeling approach of approximating a BLEVE as a sudden gas expansion, CFD may be used to predict the initial shock wave produced by the expansion to determine a detailed pressure-time histories on structures from BLEVE generated blast waves and an understanding of the far field directionality of the blast waves on the surroundings.  The results may be used to optimize vessel orientation and mitigation methods (i.e. blast walls, berms).  CFD can also be used to predict the expansion of the gas cloud behind the shock wave to determine the concentrations of the evaporated BLEVE fluid in the environment following the BLEVE event to assess the potential toxic impact on humans. Because CFD is providing the case-specific pressure-time history using the exact structures, it is not encumbered with the necessary conservatism that a generic guideline must include. Hence, the CFD results will likely produce weaker overpressures than those derived from generic guidelines, which yield a less conservative design of the structure.