A method for simulation of vapour cloud explosions based on computational fluid dynamics (CFD) S.M. Tauseef a , D. Rashtchian b , Tasneem Abbasi a , S.A. Abbasi a, * a Centre for Pollution Control and Environmental Engineering, Pondicherry University, Pondicherry 605 014, India b Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran article info Article history: Received 28 January 2011 Received in revised form 3 May 2011 Accepted 21 May 2011 Keywords: Realizable ke3 LPG Dense gas Dispersion Vapour cloud explosion CFD-based model abstract The effectiveness of the application of CFD to vapour cloud explosion (VCE) modelling depends on the accuracy with which geometrical details of the obstacles likely to be encountered by the vapour cloud are represented and the correctness with which turbulence is predicted. This is because the severity of a VCE strongly depends on the types of obstacles encountered by the cloud undergoing combustion; the turbulence generated by the obstacles influences flame speed and feeds the process of explosion through enhanced mixing of fuel and oxidant. In this paper a CFD-based method is proposed on the basis of the author’s finding that among the various models available for assessing turbulence, the realizable ke3 model yields results closer to experimental findings than the other, more frequently used, turbulence models if used in conjunction with the eddy-dissipation model. The applicability of the method has been demonstrated in simulating the dispersion and ignition of a typical vapour cloud formed as a result of a spill from a liquid petroleum gas (LPG) tank situated in a refinery. The simulation made it possible to assess the overpressures resulting from the combustion of the flammable vapour cloud. The phenom- enon of flame acceleration, which is a characteristic of combustion enhanced in the presence of obstacles, was clearly observed. Comparison of the results with an oft-used commercial software reveals that the present CFD-based method achieves a more realistic simulation of the VCE phenomena. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Among the different types of explosions that can occur in chemical process industry (Abbasi & Abbasi, 2007a, 2007b, 2007c, 2008; Khan & Abbasi, 1998, 1999a, 1999b), vapour cloud explosion (VCE) is unique in the sense that it is the only type of explosion that can take place far away from the unit which had suffered a loss of containment. This happens when a vapour cloud formed after the accidental release of a flammable substance is able to drift downwind for several minutes before meeting an ignition source. As a result process units, struc- tures, and living beings totally unconnected with the source of vapour cloud and situated far away from the source can suffer great damage due to a VCE. There are numerous past events when VCE had devastated shops (Khan & Abbasi, 1999; Lees, 2005), running trains (Hofheinz & Kohan, 1989; Lees, 2005), and other forms of public property lying well away from the origin of the vapour cloud. VCE’s have also been very frequently involved in damaging other process units and triggering several other explosions and/or fires, as had happened at Feyzin, Mexico, and elsewhere (Davenport, 1977; Khan & Abbasi, 1999; Lees, 2005; Strehlow, 1973). One of the biggest envi- ronmental disasters has recently been triggered by a VCE e the British Petroleum (BP) oil spill in the Gulf of Mexico (Schwartz & Weber, 2010). Throughout this paper the word ‘vapour’ in VCE will be used as a generic term which includes vapours, aerosol mists, and gases. As explained elsewhere (Abbasi, Pasman, & Abbasi, 2010) the physical state of an accidentally released chemical forming a flam- mable cloud with the ambient air can undergo changes, from aerosol mists to vapours/gases. For several years, right up to the early 1990s, VCEs were believed to be of two forms e the unconfined vapour cloud explosion (UVCE) and the confined vapour cloud explosion (CVCE). But controlled experiments during the late 1980s and early 1990s (Harrison & Eyre, 1987; Harris & Wickens, 1989; Mercx, 1992) using fairly large vapour clouds partially confined by arrays of obstacles made it clear that some degree of confinement was essential to achieve flame speeds fast enough to produce a blast in a VCE. In compar- ison, truly unconfined vapour clouds mustered very low flame speeds which generated negligible overpressures (Pritchard & Roberts, 1993), and resulted in only vapour cloud fire (VCF). * Corresponding author. Tel.: þ91 94432 65262; fax: þ91 413 2655263. E-mail address: prof.s.a.abbasi@gmail.com (S.A. Abbasi). Contents lists available at ScienceDirect Journal of Loss Prevention in the Process Industries journal homepage: www.elsevier.com/locate/jlp 0950-4230/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jlp.2011.05.007 Journal of Loss Prevention in the Process Industries 24 (2011) 638e647