Author(s): Daeyoung Yu; Joseph H. W. Lee
Linked Author(s): Joseph Hun-Wei Lee
Keywords: Urban drainage; Intake structure; Vortex; Tangential intake; Dropshaft
Abstract: For storm water diversion to a deep dropshaft, a tangential slot vortex intake has been considered as a hydraulically superior and cost effective alternative to conventional spiral vortex or plunging flow intakes. Tangential vortex intakes have been studied in physical models and employed successfully in practical application. By assuming energy conservation, a one-dimensional theory also provides a head-discharge relation for the intake. However, there appears to be no general guidelines available for the screening of design alternatives. In this study the hydraulics of tangential slot vortex intakes is investigated via a series of experiments, with particular reference to flow features important in design considerations. It is found that the flow in the tapering and downward sloping inlet channel is strongly dependent on the geometry of the inlet and dropshaft. Depending on the width of the approach channel and inlet slot, dropshaft diameter, and the vertical and lateral inclinations of intake, hydraulic instability and overflow can result, rendering the design ineffective. The present experiments provide a first attempt to develop general and robust design criteria for tangential vortex intakes.