Vorticity in hydraulic structures: modelling and preventing

Abstract

Free surface vortices at hydropower intakes can significantly reduce turbine efficiency and cause premature mechanical failure; in siphon spillways the vorticity and the air entrainment to the pressure circuit can reduce the spillway discharge capacity. Therefore preventing the occurrence of vortices is very important in the design of water intakes. Due to the complexity of the phenomena, physical models are a valuable help and, apart from the scale effects, vortices observations on physical models can give valuable results that aid in the design of hydraulic structures where vortices might appear. In this paper, the formation of free surface vortices in two types of submerged hydraulic structures and several solutions to prevent vortices formation are presented. The experimental studies were performed in two scaled physical models which allowed testing several solutions for anti-vortex devices that proved to be generally efficient and can be easily incorporated in the final geometry of water intakes.