Large-eddy simulation of interactions between a reacting plume and water spray

Study on water-based residential fire suppression system has received renewed attention due to environmental benefit. The progress on gaining detailed knowledge of this complex system, however, has been relatively slow. The objective of this paper is to pursue a better understanding of the interaction mechanisms between an upward reacting plume and a downward water spray, as in a practical sprinkler system, using large-eddy simulations. The flow field is described with threedimensional unsteady Navier-Stokes equations, and chemical reactions represented by finite rate chemistry. Coupling of mass, momentum and energy between the Eulerian flow and Lagrangian droplets has been taken into consideration. Dynamic subgrid scale models are employed to better describe the unsteady and local interactions without manually tuning model constants. It was found that small droplets of a diameter of 400 ?m have poor penetration capacity, while larger droplets of a diameter of 800 ?m are quite effective for fire suppression. Budget analyses of the grid scale kinetic and thermal energy reveal complex non-linear interactions between the fire plume and water droplet