Three-dimensional modelling of flow in sharp open-channel bends with vanes

Abstract

Flow around a sharp open-channel bend is highly three-dimensional (3D) due to the combined effects of secondary flow, a large free surface variation and flow separation along the inner wall. Continuous vanes often used in closed curved conduits to generate a more uniform downstream flow were tested in the open channel using a 3D finite-volume model with a Reynolds stress turbulence model and the volume of fluid method for free surface prediction. The velocity field, turbulent kinetic energy and the extent of the flow separation zone were successfully validated against laboratory measurements for the no-vane case. The 3D simulations for one-vane and three-vane configurations reveal that vertical vanes are effective to reduce the secondary flow intensity and flow separation along the inner wall. The energy loss for bends with vanes is further slightly reduced compared to the no-vane case. The three-vane configuration is particularly efficient at creating uniform downstream flow.

Keywords:

• Flow separation
• numerical simulation
• open-channel bend
• Reynolds stress model
• secondary flow
• turbulence model
• water surface