Performance evaluation of bilateral side slopes in piano key weirs by numerical simulation

The piano key weirs (PKWs) are a developed type of labyrinth weirs that the discharge capacity increases in these weirs by expanding of the length of the overflow in a specified width. In this research, the discharge capacity value is investigated for 7 types of the PKWs with different heights using numerical simulation. The simulation is performed in Flow 3D software with the k-ε turbulence model. Two statistical parameters R 2 and RMSE are used to determine the errors between numerical and experimental models. The RMSE values for models 1 to 7 (or A to G) are 0.00145, 0.0035, 0.0019, 0.0031, 0.0065, 0.0062 and 0.006, respectively, which indicate the acceptable accuracy of the numerical solution. According to the simulation and experimental results for the weirs, the F-type weir has the best performance in passing of the flow discharge. In order to increase the discharge capacity of the F-type weir, a bilateral side slope with angles of 5°, 10°, 15°, 20° and 25° is applied to the bottom of the weir output keys. The results of the numerical simulation show that the 25° slope has the best efficiency and increases the F-weir discharge capacity rate about 3.37% compared to other PKWs.