In this study, a multiphase pyrolysis model has been proposed under the large eddy simulation (LES) framework incorporating moving boundary surface tracking, char formation, and detailed chemical kinetics combustion modelling. The proposed numerical model was applied to simulate the cone calorimeter test of two kinds of materials: (i) pinewood (charring) and (ii) low-density polyethylene (non-charring). Using a cone calorimeter setup, good agreement has been achieved between the computational and the experimental results. The model is capable of predicting the formation of the char layer and thus replicating the flame suppressing thermal and barrier effects. Furthermore, with the application of detailed chemical kinetics, the fire model was able to aptly predict the generation of asphyxiant gas such as CO/CO₂ during the burning process. However, the pinewood experiments showed significant CO/CO₂ emissions post flame extinguishment attributed to char oxidation effects, which were not considered by the fire model. Despite the limitation, the fully coupled LES model proposed in this study was capable of predicting the fluid mechanics and heat transfer for the turbulent reacting flow, solid-phase decomposition, and gaseous products under flaming conditions. In the future, it can be further extended to include char oxidation mechanisms to improve predictions for charring materials.

Modern buildings and structures are commonly equipped with fire safety detection and protection systems. Owing to the complexity in building architectures, performance-based fire engineering designs are often applied to achieve safety compliance criteria in stipulated fire events. With the uprising popularity of computer simulation fire predictive models benefited by the rapid improvement in computing speed and modelling techniques, the use of computational fluid dynamics (CFD) based fire field models has become an integrated component in fire tenability and assessment studies. This article delivers a comprehensive review on the history, past developments, and current state-of-the-art of CFD models for enclosure fires, as well as providing an in-depth review on the advancement in other sub-modelling components including turbulence, combustion, radiation, and soot models. Additionally, two types of multiphase modelling approaches involving solid-gas and liquid-gas phase models are reviewed. As for the preceding, the consideration of the solid phase combustibles is generally achieved via pyrolysis modelling under the context of CFD. Recent advancements in CFD-based pyrolysis studies are extensively discussed, including the consideration of porous media, charring layer formation, and kinetics search algorithms to describe the solid decomposition and charring processes. Meanwhile, fire suppression models involving the discrete phase model (DPM) approach are reviewed. This includes previous developments in simulation methods of water droplets, coupling approaches with the fire dynamics in the large eddy simulation (LES) framework. Finally, a future perspective regarding the need to develop a melting/dripping sub-model for building materials is discussed, whose reaction kinetics can be supported by molecular dynamics (MD).

Owing to the well-established Eulerian–Lagrangian framework on mixture fluids, computational fluid dynamics coupled with discrete element model (CFD–DEM) is an effective while appropriate tool to predict the complex interactive fire behaviours associate with suppression effects. Although suppression behaviours between hydrocarbon-fuelled fire and water-based suppression agents were extensively studied both numerically and experimentally, lack of numerical studies was conducted on fires involving water-reactive chemicals (i.e., Na, Li, and LiH), where extinguishment is barely performed by water-based active suppression system, as violent and explosive decomposition occurred between water and reactive fuel. In this research, a numerical investigation has been conducted on expandable graphite (EG) application for water-reactive fire suppression. Based on the discrete phase model (DPM) framework, a novel EG particle model is proposed to characterise the particle expansion that couples with superior thermal properties and chemical stability. A numerical assessment on large eddy simulation (LES) has been performed to study the temporal fire behaviours and the suppression effect of EG against the flame plume in various subgrid-scale (SGS) models. Four SGS models were adopted, which were namely Smagorinsky–Lilly, WALE, dynamic kinetic energy, and dynamic Smagorinsky–Lilly. As a result, the WALE SGS model was observed to be in a better agreement compared with the experimental data owing to its significant enhancement in flow diffusivity modelling. The WALE SGS model has achieved a more accurate temperature prediction and finer resolved turbulence compared with other SGS models.

An advanced numerical model for modeling spontaneous condensation phenomena of water vapor was presented to investigate the flow behaviors in a converging–diverging nozzle for potential application in fire suppression using steam ejectors. The numerical model is validated against existing experimental data, which shows a good agreement. The proposed model was then compared against the ideal gas model in terms of various flow behaviors, including static pressure and Mach number in a newly designed nozzle. The condensing behaviors were accurately captured by the proposed model, while the idea gas model failed to do so. The condensation phenomena, including nucleation rate, droplet number, etc., in the nozzle, were discussed in detail. The accurate prediction results proved the possibility and demonstrated potential of applying the proposed model to broader fields of applications, especially into a steam ejector.