Numerical investigation of discharge capacity of sediment-induced blockage piano key weir

ABSTRACT Sediment accumulation at the inlet keys of piano key weirs (PKWs) can cause partial or full blockage, reducing discharge capacity and elevating upstream flood risk. This study evaluates blockage effects on the Canh Tang PKW (Vietnam) through an integrated experimental, numerical, and analytical approach. A 3D CFD model, using the volume of fluid method with RNG k–ε turbulence closure, was validated against physical model results, showing strong agreement. Simulations revealed that blockage significantly reduces efficiency, with full blockage cutting discharge by nearly 50%. Flow redistribution intensified turbulence and energy losses, potentially increasing cavitation, scour, and vibration risks. To improve predictive capability, analytical discharge equations were developed to account for blockage ratios. These formulas reproduced numerical predictions with good accuracy (NRMSE = 0.030). This work presents the first integrated framework for quantifying sediment-induced blockage in PKWs, offering practical tools for design, safety assessment, and sediment management in spillways.