Flow characteristics of a tangential vortex intake with steep-slope tapering section

Tangential vortex intakes are compact hydraulic structures commonly used in water supply, drainage and sewerage systems to convey water from high to low elevations efficiently. For certain intake design, due to the complex three-dimensional (3D) flow transition, hydraulic jump and shock waves may form. This paper presents an experimental and 3D computational fluid dynamics (CFD) modeling of the flow in a tangential vortex intake with a steep-slope (sloping angle 45°) tapering section. Swirling velocity field was measured using laser Doppler anemometry (LDA) for discharges with typical flow features. CFD predictions were most encouraging in the good agreement with measured head-discharge relationship, air core size and velocity. It was found that the flow regimes are determined by the hydraulic controls at different sections under different discharges, forming a complex flow transition with an inclined hydraulic jump at the tapering section. While the swirling flow in the dropshaft is highly asymmetrical, the local tangential velocity is similar to that of a stable tangential intake with Rankine vortex behaviour. Flow energy dissipation is caused by the hydraulic jump at the tapering section and the friction loss at the dropshaft. The present study offers comprehensive insights to the design of tangential vortex intake structures.