Abstract
Vortex drop shaft (VDS) spillways are eco-friendly hydraulic structures used for safely releasing flood. However, due to the complexity of the three-dimensional rotational flow and the lack of suitable measuring devices, current experimental work cannot interpret the flow behavior reliably inside the VDS spillway, consequently experimental and CFD study on a VDS spillway with an elliptical tangential inlet was conducted to further discern the interior three-dimensional flow behavior. Hydraulic characteristics such as wall pressure, swirl angle, annular hydraulic height and Froude number of the tapering section are experimentally obtained and acceptably agreed with the numerical prediction. Results indicated that the relative dimensionless maximum height of the standing wave falls off nearly linearly with the increasing Froude number. Nonlinear regression was established to give an estimation of the minimum air-core rate. The normalized height of the hydraulic jump depends on the flow phenomena of pressure slope. Simulated results sufficiently reveal the three-dimensional velocity field (resultant velocity, axial velocity, tangential velocity and radial velocity) with obvious regional and cross-sectional variations inside the vortex drop shaft. It is found that cross-sectional tangential velocity varies, resembling the near-cavity forced vortex and near-wall free vortex behavior. Analytic calculations for the cross-sectional pressure were developed and correlated well with simulated results.
Highlights
The Froude number (Fr) calculated by Fr = v/ gh is plotted in Figure 4, which reduces with increasing discharge
The Froude number (Fr) calculated by Fr = v / gh is plotted in Figure 4, which reduces with increasing discharge
The wall pressure and the swirl angle flow regime of the Vortex drop shaft (VDS) spillway is characterized by the standing shock wave, the air core and the annular hydraulic jump
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Unlike the previous VDS with a tangential slot inlet [9,15,29], widely applied in an urban drainage system, the hydraulic behavior of a VDS spillway equipped with an elliptical tangential inlet has not been detailed addressed Such shape originated in China, and it is generally considered superior with better discharge capacity and flow pattern than the former [1]. Meanical simulation were conducted to further discern the three-dimensional flow behavior while, experimental and simulated results such as the performance of the standing wave, of a VDS spillway, comprising a tangential vortex intake with 1/4 ellipse guiding wall, air-core ratio, cross-sectional pressure and three-dimensional velocity were comprehenand the relevant computational results are verified by experimental data. The combined vortex rule was introduced to predict the experimental and simulated results such as the performance of the standing wave, air-core cross-sectional pressure distribution of the swirling flow in the VDS. The outcomes of the current research can provide comprehensive insights for the research and application of similar engineering
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