NUMERICAL-SIMULATION OF ACTUAL DELIVERED DENSITY (ADD) MEASUREMENTS

The interaction of sprinkler spray with a buoyant plume has been numerically simulated for the case of a single sprinkler directly over the heptane spray fire of an actual delivered density (ADD) apparatus. The gas flow solution was obtained using a steady state, turbulent, axisymmetric numerical scheme. The simulated plume was modeled as arising from a volumetric source whose intensity was selected to approximate measured gas temperatures and velocities in the heptane spray fire. Droplet trajectories were computed using a Lagrangian scheme; droplet mass, moment and energy interactions were calculated using the particle-source-in-cell technique. The simulated spray approximated the axial momentum, drop size distribution and water distribution pattern of a commercial sprinkler. Calculations were made for two plume heat release rates and for spray sources at two ceiling heights. The predicted ADDs were in reasonable agreement with measurements for a ceiling height of 3.05 m. However, for a ceiling height of 4.57 m, the calculations consistently underpredicted the ADD.