Vortex Drop Shaft Structures: State-of-the-Art and Future Trends

Mulligan, Seán; Plant, Joss; Clifford, Eoghan

doi:10.3850/38wc092019-1813

Cited by 4 publications

(2 citation statements)

References 17 publications

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“…The inlet structure conveys the approach flow through a sloped free-surface inlet channel, and it generates the swirl flow. Mulligan et al [12] recapitulated the different configurations of the inlet device as proposed in the technical literature. All of them, anyway, transfer an angular momentum to the approach flow which is forced to adhere to the outer wall and spiral downward along the shaft [13].…”

Section: Introductionmentioning

confidence: 99%

Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Crispino

Contestabile

Vicinanza

et al. 2021

Water

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Vortex drop shafts are special manholes designed to link sewer channels at different elevations. Significant energy head dissipation occurs across these structures, mainly due to vertical shaft wall friction and turbulence in the dissipation chamber at the toe of the shaft. In the present study two aspects, sometimes neglected in the standard hydraulic design, are considered, namely the energy head dissipation efficiency and the maximum pressure force in the dissipation chamber. Different physical model results derived from the pertinent literature are analyzed. It is demonstrated that the energy head dissipation efficiency is mostly related to the flow impact and turbulence occurring in the chamber. Similarly to the drop manholes, a relation derived from a simple theoretical model is proposed for the estimation of the energy head loss coefficient. The analysis of the pressures measured on the chamber bottom allows to provide a useful equation to estimate the pressure peak in the chamber as a function of the approach flow energy head.

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Section: Introductionmentioning

confidence: 99%

Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Crispino

Contestabile

Vicinanza

et al. 2021

Water

View full text Add to dashboard Cite

show abstract

“…The elevation difference for VDS sewer applications is typically larger than 5 to 20 m (Gisonni and Hager 2012). VDSs can also be used as flood spillways at dams (Mulligan et al 2019). For such structures, the shaft height is considerably larger than in sewer applications.…”

Section: Introductionmentioning

confidence: 99%

Bottom pressure characteristics in a stilling basin downstream of a stepped spillway for two different chute slopes

Stojnić¹,

Pfister²,

Matos³

et al. 2020

Proceedings of the 8th IAHR International Symposium on Hydraulic Structures ISHS2020

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The vortex drop shaft is a benchmark structure in hydraulic engineering. It is often used in sewers and hydropower systems, given that a significant energy dissipation combined with a reduced space occupation is achieved. Conversely, the flow pattern establishing along the structure may lead to the occurrence of unstable phenomena as vibrations, abrasion and choking, particularly if the operational conditions are different from the standard design regime. It is advantageous to study the overall hydraulic efficiency of the structure, and particularly to derive the hydraulic conditions of the swirling flow along the vertical shaft. At this regard, the paper describes a physically based approach, based on the momentum conservation, to derive the rotational angle and the velocity profiles along the shaft. The method requires the calibration of an empirical parameter accounting for the increase of the wall friction stress due to the centrifugal force. The outcomes of the application of the proposed procedure are presented with reference to the operation of two physical models of supercritical vortex drop shafts, with a tangential or a spiral inlet at the shaft top. It is shown that the application of the empirically-modified momentum approach is necessary for accounting for the significant angular momentum imparted to the swirling flow by the spiral inlet and for modelling the rotational flow distribution along the vertical shaft accurately.

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Optimal design of deep stormwater drainage tunnels to address urban flooding in Korea

Cho

2024

Sci Rep

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Deep stormwater drainage tunnels play a crucial role in mitigating severe urban flooding in Korea, particularly as climate change leads to more extreme weather events. These tunnels typically consist of an entrance reservoir, a circular reinforced concrete culvert with a flat slope, a downstream reservoir, and an outlet to a nearby river. In this system, the flow within the circular culvert is driven solely by the momentum of free-falling stormwater runoff. However, concerns have emerged within the Korean water resources engineering community about the drainage capacity of these tunnels, even with a substantial fall height of approximately 30 m. Intensified localized rainfall, the abrupt transition from flood waves to pressurized flow within the circular culvert, and trapped air pockets can also pose significant challenges to the tunnel’s drainage efficiency. Conventional design methods often fail to optimize the culvert’s diameter and spatial configuration, leading to suboptimal performance. In response, this study utilizes 3D numerical simulations with the interFoam solver from the OpenFOAM toolbox to address these issues. The results indicate that smaller culvert diameters—provided they do not exceed the maximum permissible flow velocity—enhance drainage capacity by reducing the impact of shock waves and stabilizing flow. These findings challenge the prevailing design practice in Korea, which holds that larger culverts inherently offer superior drainage capacity. Moreover, the simulations suggest that as culvert diameters increase, the size of trapped air pockets grows, further reducing efficiency. Although air chambers can help mitigate the retarding effects of trapped air pockets, their effectiveness diminishes if positioned near the origin of shock waves, where they risk being filled with stormwater. Based on these insights, several key recommendations are proposed: First, the design of deep stormwater tunnels should prioritize minimizing the extent of trapped air pockets, even when air chambers are used. Second, the current focus on detention capacity in design practices should be reevaluated, as excessive detention capacity may exacerbate air pocket formation. Finally, modifying the inlet channel to induce spiral flow within the entrance reservoir could reduce impulsive forces, lower maintenance costs related to armoring rocks at the reservoir bottom, and stabilize flow more quickly, thereby enhancing overall drainage capacity.

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Vortex Drop Shaft Structures: State-of-the-Art and Future Trends

Cited by 4 publications

References 17 publications

Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Bottom pressure characteristics in a stilling basin downstream of a stepped spillway for two different chute slopes

Optimal design of deep stormwater drainage tunnels to address urban flooding in Korea

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