Predictive Computational Fluid Dynamics Simulation of Fire Spread on Wood Cribs

Abstract

Presently, there is a need for a robust numerical simulation approach to investigate the influence of various parameters on fire spread in large open framed structures. CFD-based methods can already be used for analyzing the fire conditions but they are difficult to apply for large calculations where the geometrical details of the fuel are sub-grid scale. In this paper we present a CFD-based fire spread simulation method that makes use of the ignition temperature model for pyrolysis and introduce a correction for the mesh dependency of the fuel surface area. Wood sticks, with an ignition temperature of 300°C and a specified heat release rate per unit area of 260 kW/m 2 , were used as fire load. The method was validated using laboratory scale tunnel (10 m  0.6 m  0.396 m) fire tests with a longitudinal velocity of 0.6 m/s, demonstrating a 3% bias for the peak heat release rates and less than 33% biases for the fire growth rate. The method was then applied to room-scale fire spread simulations with uniformly distributed wood cribs at 600 MJ/m 2. The results show that, with the help of the surface area correction, the fine-mesh predictions of the heat release rate and thermal environment can be reproduced with coarser meshes and one order of magnitude lower computational costs. Due to the inherent inability of the large-scale CFD to resolve the flame temperature, there is a minimum size of the initial, prescribed fire area which is required for consistent fire spread predictions. Through this study, the authors attempt to build a reliable CFD modelling approach for fire spread and traveling fires.

Modelling the Effects of Boundary Walls on the Fire Dynamics of Informal Settlement Dwellings

“…In this work, this method is implemented to model the fire spread over the wood cribs with a coarser mesh, which is expected to increase the efficiency of the simulations. The study by Kallada Janardhan & Hostikka [35] validated the use of the ignition temperature model and the proposed area adjust method for coarse mesh fire spread simulations and performed room scale fire spread simulations. Compared to the fine mesh simulations, the proposed method reduced the CPU time by approximately 80%.…”

“…In order to reduce the computational effort, Kallada Janardhan & Hostikka [35] proposed a predictive CFD simulation for the fire spread on wood cribs by conducting a correction for the mesh dependency of the fuel surface area for the case where the CFD grid cells are larger than the sticks that makes use of the ignition temperature for pyrolysis. In this work, this method is implemented to model the fire spread over the wood cribs with a coarser mesh, which is expected to increase the efficiency of the simulations.…”

Numerical simulation of the fire behaviour of façade equipped with aluminium composite material‐based claddings—Model validation at intermediate scale

“…The change in the ignition temperature or other thermal parameter will be investigated while changing the mesh resolution. The approaches for the use of ignition temperature model accompanied by area adjust for coarse mesh fire spread simulations following the work of Janardhan and Hostikka will be investigated.…”

Numerical simulation of the fire behaviour of facade equipped with aluminium composite material‐based claddings‐Model validation at large scale

“…The main objective is to reproduce the thermal gradients achieved with the initial model, in the gas phase. As discussed in Janardhan and Hostikka,36 the change in the ignition temperature or other thermal parameter is needed while changing the mesh resolution. The investigated approach for the use of coarse mesh in fire spread simulations is to consider artificially an area adjust coefficient reported in thermal parameter.…”