Comment on “Hydraulic characteristics of labyrinth sluice gates” by T. Hashem, A.Y. Mohammed, T.J. Alfatlawi

In this paper, the stage-discharge relationship of a labyrinth sluice gate is theoretically deduced by the Π-Theorem of dimensional analysis and the self-similarity condition. This approach was then compared with the classical approach using the discharge coefficient Cd proposed by Hashem et al. (2024). The classical stage-discharge equation (Eq. 4), with the discharge coefficient estimated by the empirical relationship (Eq. (1)) proposed by Hashem et al. (2024), resulted in errors E that are less than or equal to ±5 % for 74.3 % of the investigated cases and a mean square error MSE of 0.0078. The new stage-discharge relationship, deduced by dimensional analysis and self-similarity theory, was calibrated using the dataset by Hashem et al. (2024). The obtained stage-discharge equation (Eq. 20) is characterized by errors in the discharge estimate E that are less than or equal to ±5 % for 82.2 % of the investigated cases and a mean square error MSE of 0.0051. In conclusion, the stage-discharge relationship deduced by dimensional analysis allows for the best performance in the discharge estimate, which can be obtained without knowledge of the empirical discharge coefficient.