Numerical Estimation of Environmental Wind Effect on Smoke Evolution in a 10-storey Building

Abstract

This contribution addresses the influence of environmental wind on the smoke propagation process in a 10-storey apartment through a Computational Fluid Dynamics (CFD) simulator, Fire Dynamics Simulator (FDS). A 6 MW fire source is prescribed in a compartment on the first floor with the window confronting the incoming air flow. Windward and leeward wind conditions are designed to examine the influential aspects of wind. Two parallel stairwells separated by a corridor are located at the center of the apartment and allow the smoke to spread to the upper floors. Several important parameters featuring the smoke propagation characteristics, including the smoke temperature, CO concentration and visibility in fire compartment, corridor, stairwells and upper layers, are recorded by the preset monitoring points and snapshots of the simulation results. An analytical model is employed to estimate the break time of window at 380 °C tolerance temperature, which is utilized subsequently in the numerical simulations to determine the onset of wind intervention. The results show that the leeward condition has negligible effect on the smoke evolution in the computation domain compared with the results of no-wind cases. However, in windward conditions the wind velocity has significant influence on the interested parameters and little smoke flows out form the broken window. The smoke spread rate and visibility inside the building are positively and negatively correlated with the wind velocity, respectively. The wind velocity affects the smoke temperature slightly, but greatly affects the temperature in the corridor, the opposite room and stairwell. The smoke spread in stairwell takes less than 1 minute due to the strong buoyancy, suggesting sever hazard in practical accident. The CO concentrations in all the cases shows similar trend to that of smoke temperature at each monitoring points, and the CO concentration level is much higher than the critical value for human safety, 500 ppm.