Hydraulic Design of Underground Flood way in a Metropolitan Area

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Hydraulic transients in the underground channel system such as the underground flood way and the sewer network were investigated experimentally and numerically. The typical features of the unsteady flows induced by the inflow discharge into the underground channel are clarified by the fundamental hydraulic experiments. It is also shown that the hydraulic transients with the propagation of an interface between the open channel flow and the pipe flow can be reproduced by using the numerical model. It was pointed out that the form losses of fluid energy at the junction of the main channel and the vertical shafts should be considered to predict the surging phenomena induced by the rapid change of the outflow discharge.Numerical model was extended to predict the interaction between the overland surface flow and the flow in the underground channel., considering the discharge through the manholes.The hydraulic characteristics of vertical drofshaft with tangential vortex-inlet, which is used to let the flood water flow into the underground channel, were also investigated experimentally. The relation between the air entrainment rate and the hydraulic conditions was proposed through the examination of the hydraulic experiments.