Influence of radiation modelling in under-resolved FDS free-burn simulations

Abstract

Focusing on the impact of radiation modelling in under-resolved fire simulations, the paper presents LES of free-burn scenarios. The work aims to evaluate the performance of the current fire modelling capabilities of the Fire Dynamics Simulator (FDS) code and to identify the best practices for FDS practitioners in terms of simulating radiative heat transfer. To this purpose, both optically thin and optically thick approaches are considered and their predictive capabilities over different grid sizes is evaluated. The impact of various radiation modelling parameters with the optically thick approach (i.e., path length, number of solid angles) is also considered. Comparisons of the predicted centreline flame temperatures and axial velocities as well as of the predicted radiative heat fluxes at different locations are presented. Overall, there were obvious differences between the two approaches with the optically thin being more accurate when compared to both experimental data and empirical correlations available in the literature.