This study considers the thermal and fluid dynamics of a simulated fire (a thermal plume) and its interactions with a watermist spray. The thermal plume was modeled by a placing a hot surface on the floor of an open cubic space bounded by a floor and a ceiling. The watermist injector was placed close to the ceiling. Simulations were performed with various thermal load conditions on the hot surface. The watermist was introduced in the computational domain by using an agent delivery model developed in-house. This model was coupled with the fire dynamics simulator code. Dynamics of watermist spray was represented by Lagrangian particles, coupled with an Eulerian gas-phase flow solver. Turbulence was treated by large eddy simulation approach with Smagorinsky model. Major findings from this study highlighted radiation attenuation as the dominant suppression mechanism for a watermist based system. The results also showed that penetration of watermist jet into the buoyant plume is a function of droplet size, droplet momentum, gas entrainment, nozzle location as well as the thermal loading and location of the source of heat.
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