Discharge Characteristics of Triangular Weir with Upstream Ramp and Its CFD Modelling Using Ansys CFX Module

Abstract

To understand the flow field and discharge characteristics of a triangular weir with an upstream ramp (TW-UR), experimental study as well as computational fluid dynamics (CFD) simulation were performed. The Ansys CFX module and standard k-ε turbulent model were used in the simulation. It was observed that the TW-UR had about 9.8–14.3% higher discharging capacity than a sharp-crested weir of the same height and it was found that about 10–15% higher discharging capacity was estimated in the CFD simulation as compared to the observed data under the same head. The highly active flow field in the upstream side and enhanced velocity along the flow direction due to flow contraction in the vertical plane are helpful in enhancing the hydrodynamic force exerted by the moving fluid and creating the chances of sediment passage as well as increasing the discharging capacity. Existing two equations of the coefficient of discharge for TW-UR were checked for their accuracy using the present and previous experimental data, and it was observed that the equation proposed by Azimi et al. (J Irrig Drain Eng 139(1):75–83, 2013) predicted the coefficient of discharge within ±5, ±10 and ±15% error ranges for 43.0, 72.5 and 92.5% datasets, whereas within those error ranges, equation proposed by Di Stefano et al. (J Irrig Drain Eng 142(10):04016036-1–9, 2016) estimated the coefficient of discharge for 61.7, 92.3 and 100% datasets, respectively. Statistical analysis showed that in most of the cases, the equation of Di Stefano et al. (J Irrig Drain Eng 142(10):04016036-1–9, 2016) showed better precision than Azimi et al. (J Irrig Drain Eng 139(1):75–83, 2013) equation, and overall, the equation proposed by Di Stefano et al. (J Irrig Drain Eng 142(10):04016036-1–9, 2016) is more accurate than the equation proposed by Azimi et al. (J Irrig Drain Eng 139(1):75–83, 2013).