Modeling the coanda effect with FDS and STARCCM+ to predict the effect of fires on slopes for implications of wildland firefighter safety

The Coanda effect is the behavior of a fluid flowing next to a solid surface which creates a change in pressure, thereby causing the fluid to attach to the surface. Little is known concerning the Coanda effect as it pertains to flame attachment in relation to wildfires. There is a need for improvement in the correlations between fire behavior on or near a slope and fire safety zones. An understanding of this effect could lead to more reliable guidelines for the establishment of firefighter safety zones, which are regions in wildfire areas that have been determined as safe for the survival of the firefighter. This paper discusses the ability of two commercial computational fluid dynamics (CFD) codes (Fire Dynamics Simulator (FDS) and STAR-CCM+) to model the results of actual flame experiments near barren slopes. Simulation results were compared to measured values of flame attachment length and radiative and convective heat fluxes. Pressure and temperature gradient measurements along the slope are reported. Proper modeling of small-scale experiments with such software packages can lead to more confidence in large scale simulations and eventual development of firefighter safety zones in wildfires.