Experimental study on the discharge coefficient of triangular piano key weir*

The present study aims to experimentally evaluate the hydraulic characteristics of a B-type triangular piano key weir (PKW). Equations are proposed for estimating the discharge coefficient (C-d) of type B triangular PKW. Nine PKW models were tested, and the discharge coefficients were obtained. To determine the PKW efficiency, in each flow condition, the experiment was repeated for a linear weir having the same height as the PKW. In particular, the flow rate of the triangular PKW was up to three times higher than that of the linear weir. Studying the flow behaviour showed that the sloping triangular surface of the PKW helps with the quick transfer of flow from the channel bed, especially in the outside keys. In addition, increasing the dimensionless parameters h/L-e and h/P reduces the discharge coefficient in the weir. Empirical equations are presented for the triangular PKW discharge coefficient. For the regression analysis, analysis of variance was performed to list the most important variables. Subsequently, by performing sensitivity analysis, the most important dimensionless parameter for estimating the discharge coefficient was obtained. The group method of data handling was applied to the data to achieve higher accuracy. Finally, uncertainty analysis was conducted using the asymmetric loss function.