• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1043-1050
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• 2014

An air-core vortex is generated during draining after stirring a rotating cylindrical tank or after filling it with water. The formation of the air-core vortex and the time of its formation are dependent on drain conditions such as the dimensions of the tank, the initial rotation or stirring speed, and the shape of the drain port. In this study, a draining process using a two-stage drain port was numerically investigated. The length and radius of the first drain stage located in the lower part of the drain port were kept constant, whereas the radius of the second drain stage was varied for simulating the draining process. The simulation was conducted by considering an axisymmetric swirling flow for all cases. The declining water level was monitored by an interface capturing method. Further, the effects of the radius of the second drain stage on the time of formation of the air-core vortex and the internal flow structure were investigated.

• Journal of Korea Water Resources Association
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• v.52 no.3
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• pp.227-234
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• 2019

The vulnerability of urban disasters is increased with the rapid urbanization and industrialization, and the extreme rainfall event is increased due to the global climate change. Urban inundation is also increased due to the extreme rainfall event beyond the capacity limit of facility for the damage prevention. The underground detention vault and the underground drain tunnel are rapidly being utilized to prevent urban inundation. Therefore, the hydraulic review and design analysis of the inlet of the underground facility are important. In this study, the water level of the approach flow according to the inflow discharge is measured and the flow characteristic of the inlet (tangential and spiral) is analyzed. For the spiral inlet, the multi-stage is introduced at the bottom of the inlet to improve the inducing vortex flow at low discharge conditions. In case of the tangential inlet, the discharging efficiency is decreased rapidly with hydraulic jump in the high flow discharge. The rising ratio of the water level in the multi-stage spiral inlet is higher than the tangential inlet, but the stable discharging efficiency is maintained at low and high discharge conditions. And the empirical formula of water level-flow discharge is derived in order to utilize inlets used in this study.