Numerical study of water spray interaction with fire plume in dual chambers connected to tall shaft

•Drag force from water particles opposes buoyancy force.•Smoke logging visualized at higher sprinkler operating pressure.•Lower ventilation velocities eliminate smoke logging.•Higher ventilation velocities intensify cooling effect, increases the water spray and thermal plume interactions.

The interactions between water droplets and fire plume in a two compartmental enclosure connected to tall shaft are numerically investigated. The cooling and drag effects of water particles on thermal plume characteristics are analyzed under natural and forced ventilation conditions. Numerical study is performed by Large Eddy Simulation (LES) using Fire Dynamic Simulator (FDS) code. The water droplets oppose the smoke buoyancy force and reduces the ceiling vent discharge rate. For higher sprinkler operating pressure the drag force dominates buoyancy force and stops the plume propagation through horizontal passage. The critical sprinkler operating pressure that leads to smoke logging is identified. The horizontal vent mass flow rate decreases linearly with water spray discharge rate. The forced air stream supplied at low velocity assists buoyancy force and eliminates smoke logging. However, higher ventilation velocities intensify cooling effect by increasing the interactions between water droplets and thermal plume. The model employed has been validated with the existing experimental results available in the literature.