Free surface and velocity field in a circular channel along the side weir in supercritical flow conditions

Abstract

A side weir is a kind of flow regulator hydraulic structure which is used in drainage systems, irrigation and sewage disposal network. The passing flow over side weir is a spatial variability flow with discharge reduction. Circular channels with side weir have been used widely for regulating runoff and flood. In this research the flow free surface and the passing flow field through a circular channel with side weir is simulated by commercial software. In this CFD analysis, the RNG k–ε turbulence model is used for simulating the turbulence of the flow field and the free surface changes are modeled using VOF model. Comparison between changes in the free surface, the passing discharge over the weir, the discharge coefficient and the specific energy at the beginning section of side weir obtained from the numerical simulation and experimental results indicates acceptable accuracy of the CFD model in the supercritical regime. Given that most previous numerical studies have been focused on the rectangular channel with side weir and in the subcritical flow condition, the main purpose of this simulation is study of the free surface changes and the velocity field along a side weir located on a circular channel in the supercritical regime.