Assessment of the safe evacuation of people walking through flooding staircases based on numerical simulation

A numerical model was developed to evaluate the possibility of people walking in a flooding flow on a staircase with rest platforms. Commercial software was used and validated by experimental data for flows on staircases and stepped spillways. The effects of the rest platform, the staircase slope, and the staircase pattern on the flooding flow characteristics are discussed. A comparison of staircases with or without rest platforms shows that the flow velocity increases significantly downstream of the rest platform on a straight-run type, which would have negative effects on the safe evacuation of people walking through a flooding staircase. The slope of the staircase, ranging from 26.6° to 30°, has less effect on safe evacuation. A comparison of flows on straight-run (with or without rest platforms), 90°-turn and 180°-turn staircases (with rest platforms) shows that the rest platforms on the latter two staircases could induce a redistribution of the flow field on the rest platform and downstream. The distribution of evacuation indicators along the longitudinal planes of those staircases indicates that a 90°-turn staircase or a straight staircase without rest platform would be the first choice for trapped people evacuating from underground spaces.