Experimental study of determining the discharge coefficient relationship of trapezoidal Piano Key Weirs and sensitivity of effective parameters in it

Piano Key Weirs, a developed scheme of labyrinth weirs. In this study, 36 trapezoidal Piano Key Weirs models were conducted in 360 different geometric and hydraulic conditions. Experiments were conducted in a 11 m long flume with a rectangular cross section of 49 cm width and 70 cm height in which the effect of dimensionless ratios on the discharge coefficient was investigated. The results showed that L/W=6.54, B/P=2.33 and Wi/Wo=1.33 compared with other values ​​that have been tested in this study, increasing the discharge coefficient 113, 63 and 33 percent respectively, Therefore, they are suggested as optimal ratio for trapezoidal plan. Which is close to the ratio that other researchers have proposed for the rectangular plan. Also, by using SPSS software and taking correlation coefficient (R2) and Normalized Root Mean Square Error (NRMSE), relations was proposed to estimate the discharge coefficient and the sensitivity of the proposed relationship to its parameters showed that this relation shows the highest and lowest sensitivity to the L/W and Wi/Wo parameters respectively.