Abstract
In this study, the drainage efficiency of the multi-stage intake structure, which transports flood to the underground storage, was investigated from the laboratory experiments. The multi-stage intake structure was designed based on the tangential intake and the steps on the bed were purposes to decrease the energy of approaching flow. The experimental results show that the maximum water depth was effectively decreased in the entrance of the drop shaft. The measurements results of the air core width in the drop shaft show that the flow was stably drained without the choking. Furthermore, the air core width tends to increase with the Froude number, and these results indicate that the multi-stage intake structure is applicable to convey the approaching flow with relatively high velocity.
Highlights
Urban inundation damage is increasing due to climate change and rapid urbanization
In case of Case Q16, the portion of the minimum air core width decreases to 19.2% from 36.3% of the vertical shaft diameter
The drainage efficiency was evaluated by the measurements, which are the water depth in the intake structure and the air core width in the vertical shaft
Summary
Urban inundation damage is increasing due to climate change and rapid urbanization. These urban environment change leads to the decrease of reservoir capacity of the river basin and the lack of drainage capacity in urban areas. It is important to analyse the flow characteristics in the drop shaft to increase the discharge efficiency. For the efficient drainage system, the shape of intake structure is important to increase flowrate to the drop shaft. Several researches [2, 3, 4] conducted laboratory experiments to suggest the optimal design of the tangential intake structure. In case of the spiral inlet, [6] presented the efficient design for the intake structure, and [7] suggested the theoretical formula for the free surface profile along the intake wall. Previous researches attempted to suggest several designs for the intake structure to enhance the drainage efficiency in the drop shaft. The water surface change in the approach channel and the inlet of drop shaft were measured in various flow conditions. Performance of the intake structure was assessed by the water level increase and air core size
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