Hydrogen Safety Engineering and Research (HySAFER)
Research Topics 2012
Modelling and LES of the Buncefield Explosion
Supervisor 1: Professor Vladimir Molkov
Supervisor 2: Dr Dmitriy Makarov
Mechanisms underlying the largest recent explosion in Buncefield (http://www.buncefieldinvestigation.gov.uk/reports/buncefieldagr.pdf) have yet to be understood and physical models should be developed that could allow predictive numerical simulations in similar conditions. A heavier than air layer of hydrocarbon vapour combusted, resulting in unexpectedly high overpressures during the Buncefield incident. Different mechanisms have been suggested to explain the phenomenon, including “radiative ignition” with the involvement of porous combustible particles, etc. Some of the suggested mechanisms are highly speculative and controversial. In this study the candidate will aim to apply and develop further the multi-phenomena turbulent burning velocity model of deflagration by the University of Ulster to gain insight into underlying physical mechanisms and potential consequences. A sub-grid scale (SGS) modelling will be applied for numerically unresolved at large scales phenomena. Most models of premixed turbulent combustion are built on the dependence of turbulent burning velocity of fluctuating, i.e. root mean square, velocity derived from the assumption of isotropic turbulence. Other models take into account dependence of combustion rate on characteristic length scales. More recent models comprise the conclusions of the fractals theory with at least two characteristic scales, i.e. inner and outer cut-offs. Still there are questions on the role of resolved and sub-grid scale anisotropic effects on the turbulent burning velocity, etc. The objective of this PhD study is further development of the Ulster LES deflagration model, which accounts for unresolved anisotropy of flow in the area of combustion and its verification against information available from analysis of the Buncefield explosion. Special attention will be paid to the unresolved fractal structure of the flame front with the dynamic change of outer and inner cut-offs.
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