Buoyancy-driven flow through a ceiling aperture in a corridor: A study on smoke propagation and prevention

Analyzing numerous computational fluid dynamics (CFD) simulations of a two-level corridor model, smoke propagation and prevention were investigated. In all simulations, the fire source was placed inside the lower corridor, which we refer to as the fire corridor. Results show that after smoke flows in through the ceiling aperture, a dangerous environment forms quickly in the upper corridor. The smoke layer in the upper corridor descends nearly to floor level through buoyancy and air flowing in through the doorways. The fire hazard created in the upper level is larger than that of the fire corridor. In regard to fire prevention, the effectiveness of a counter airflow at the ceiling aperture is demonstrated, and critical velocities for counter airflow are derived through CFD simulations. A simple model for predicting this critical velocity is proposed based on the Froude modeling. The critical Froude number initially declines linearly with the dimensionless distance between the fire source and the ceiling aperture, and then stabilizes at 0.38 when this distance is larger than 3.00. This model can be used for coarse design of the counter airflow smoke control system.