A Model for Predicting the Trajectory and Structure of Firefighting Hose Streams

A model providing detailed description of the trajectory and the internal composition of firefighting hose streams in air quiescent conditions is presented. The proposed model is based on a 1D Eulerian approach over the stream’s trajectory path, allowing for simultaneous multi-phase description of the fire stream (water-core phase, spray phase and air phase), including air entrainment, jet break-up, spray generation and multi-dispersion. A series of 6 large nozzle streams were studied experimentally. Predicted and measured stream trajectories were compared using Mean Absolute Percentage Deviation (MAPD) and Maximum Absolute Error (MAE) performance criteria. Among the 6 tests, a MAPD peak value of 4.6% and MAE of 17 cm were found, showing a good agreement with experimental measurements. Internal composition of a fire stream was studied numerically. Results suggested a predominance of water-core phase initially, accounting 50% of the fire stream’s mass just before its break-up. In contrast, an increasingly leading role of air phase through the trajectory path was found, accounting 90% of the fire stream’s mass at ground level. In addition, results suggested that 49% of the injected water flow was evacuated from the stream consequence of the progressive generation of the spray along the trajectory.