Unsteady flow past a sharp crested weir

Abstract

The present study focuses on the numerical simulation of flow past a rectangular sharp crested weir. A commercial software Star-CCM+ is used for the purpose. The governing equations are the Reynolds Averaged Navier-Stokes equations. Volume of Fluid approach for free surface tracking and K-epsilon model for turbulence are used. A finite volume method is employed to solve the governing equations numerically. First, the results for the steady state flow are validated against previously published experimental results. Both rectangular and triangular sharp crested weir are used for this. Based on the 15 cases considered in the present study for steady flow, an equation for the coefficient of discharge as function of various non-dimensional parameters is developed. Other results for steady flow include velocity distribution, surface profiles and turbulence characteristics. Two different kinds of unsteady flows are considered: (i) by changing the geometry of weir with time (ii) by introducing a flood wave at the inlet. The first study shows that the discharge is increased compared to that of a steady flow case. An equation for the coefficient of discharge for unsteady flow is derived based on the simulated results. The second study focuses on sensitivity analysis of flood wave approximated as a half sine curve.