Flow Features of an Unstable Tangential Vortex Intake

Abstract

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 design of tangential vortex intakes, flow instability can occur in the approach channel and the vortex dropshaft, resulting in undesirable hydraulic jump and shock waves. Due to the complex three-dimensional (3D) flow in the tangential vortex intake, current theoretical models are not sufficiently complete to interpret the flow process reliably. This paper presents an experimental and 3D Computational Fluid Dynamics (CFD) modeling study of an unstable tangential vortex intake flow. The CFD predictions are in good agreement with detailed point velocity and air core size measurements. Despite of the hydraulic jump at the tapering channel, the swirling flow at the vortex drop shaft is similar to that of a stable vortex intake with Rankine vortex behaviour.