Numerical Simulation of Smoke Downdrag due to a Sprinkler Spray using FDS

Sprinkler interaction with a moving smoke layer, which might lead to smoke downdrag, is numerically simulated by using a large eddy simulation (LES) computational fluid dynamics model, Fire Dynamics Simulator (FDS). The simulations have focused on computing the gas temperature and the smoke layer depth induced by sprinkler discharge into a hot smoke layer. Results are presented for different water flow rates in addition to a simulation of a 'no sprinkler' case. The results of the simulations are compared to measurements from a set of full-scale experiments conducted in previous research and they show that FDS gives fairly good predictions for the upper layer temperature. However FDS underestimates the stability of smoke layer and leads to smoke downdrag regardless of the water flow rate so that the lower region temperatures are higher than those measured in the experiments