Conducting experimental and numerical studies to analyze the impact of the base nose shape on flow hydraulics in PKW weir using FLOW 3D

Weirs serve as fundamental structures for channeling excess flow from behind dams to downstream areas. In this study, a numerical and laboratory investigation was conducted to explore the impact of different base nose shapes installed under the outlet keys and varying Wi/Wo ratios on discharges ranging from 5 to 80 liters/second. For numerical simulation, the optimal number of cells for meshing was determined, and a suitable turbulence model was selected. The results demonstrated that the numerical model effectively simulated the laboratory sample with a high degree of accuracy. Furthermore, the numerical model closely approximated PKW for all parameters Q, H, and Cd when compared to the laboratory sample. The findings revealed that, in laboratory models with a maximum discharge area of 80 liters per second, the weir with Wi/Wo=1.2 and a 285 mm valve exhibited the lowest value, whereas the weir with Wi/Wo=0.71 and a 305 mm valve showed the highest, owing to the higher discharge in the input-output ratio. Additionally, as the ratio of flow head to H/P weir height increased, the discharge coefficient Cd decreased. In comparing the flow conditions in weirs with different base nose shapes, it was observed that the weir with a spindle nose shape outperformed the piano key weir with a flat, semi-cylindrical, and triangular base nose. The coefficient of discharge in PKW1.2S and PKW1.2TR weirs, compared to the PKW1.20 weir, increased by 27% and 20%, respectively.