INUNDATION ANALYSIS OF UNDERGROUND SPACE BY SHALLOW WATER EQUATION CONSIDERING STAIRCASE FLOW

Abstract

 The 2D shallow water equation (SWE) is being used in inundation analysis in underground spaces. However, inflow through staircases is estimated by overflow equations and this method ignores the momentum generated by the flow at the staircase. In this study, the results of a staircase flow using the 3D Reynolds-averaged Navier-Stokes (RANS) equation and the 2D SWE were compared, and a formula was created for estimating Manning's roughness coefficient that can correctly reproduce the energy loss of 3D RANS analysis. Using the formula, a flooding analysis was performed in a modelled subway station using the 2D SWE, and an obtained distribution of walking difficulty generally agreed with the one by 3D RANS. It was also found that the 2D SWE model in which the inflow was directly added to the underground space underestimated the walking difficulty and dangerous areas might be overlooked.