Determining the optimal design characteristics of trapezoidal piano key weirs for improved water discharge

Abstract This study attempts to evaluate the influence of design factors and flow characteristics on the discharge capacity of trapezoidal piano key weirs. To evaluate the influence of the main design factors on discharge rates, 9 models were simulated, with width ratios of 1.25, 1.75, and 2.25 and sidewall angles of 2, 4, and −2°. As the auxiliary design factors, the square Sq-parapet from previous research and the newly proposed triangular Tri-parapet were integrated into the models with high discharge capacity. We used the computational fluid dynamics simulation to analyze the fluid dynamics and provide the optimal design characteristics for trapezoidal piano key weirs. Our findings reveal that certain changes in the design, namely in the sidewall angle and width ratio, can increase the discharge rates by up to 14.7 and 13.6%, respectively. Furthermore, as a result of applying Sq-parapet and Tri-parapet to the model weirs, we found that the discharge efficiency of Tri-parapet was significantly higher compared to the existing Sq-parapet models, with improvement of up to 53.8 and 49.5%. This study contributes to understanding the influence of various design factors on the discharge capacity of trapezoidal PK weirs and offers insights for optimizing their design.