Experimental Studies on the Formation of Air-core inside the Drop Shaft

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.