Investigating the effect of computational grid sizes on the predicted characteristics of thermal radiation for a fire

Recently, the phenomenological modeling of fires has been shifted from the engineering application of correlation-based methods to the computational fluid dynamics (CFD) techniques. Therefore, the majority of this paper is to investigate the effects of grid sizes on the predicted radiative characteristics involved in a fire using CFD simulations, with the aim of selecting the appropriate grid size under the consideration of prediction accuracy and computing cost. Based on the present simulations, the predicted flame height increases as the decreasing grid size and would approach to a quasi-steady value if the simulation grids are adopted to be small enough. Similar results are also revealed in the radiative heat flux behaviors. The predicted distributions of radiative heat fluxes have no significant variations as the grid size is reduced to some small value. Several experiments of small pool fires with various diameters (20-38 cm) are conducted to assess the present CFD predictions. Using the appropriate grid size, the predicted results for radiative heat fluxes and flame heights show good agreement with the experimental data for different-size pool fires. This grid size suggested in this paper could assist the CFD simulations of pool fires in obtaining the accurate enough predictions with reasonable computing time.