A labyrinth weir is a linear weir folded in plan-view which increases the crest length and the flow rate for a given channel width and an upstream flow depth. The present study aimed at determining discharge coefficients of labyrinth and arced labyrinth weirs using support vector machine (SVM)-based models. A total of 527 laboratory test data of four types of weirs, namely, Normal and Inverted orientation Labyrinth Weirs in flume (NLW, ILW) and Arced Labyrinth Weirs with and without nappe Breakers in reservoir (ALW, ALWB), were captured from the published literature and utilized to feed the SVM-based models. The obtained results revealed the capability of the SVM-based models in determining discharge coefficients. The results showed that the SVM-based model of arced labyrinth weir (ALW) produced the most accurate results when three dimensionless parameters, e.g. (HT/P) head water ratio, (α/θ) angle ratio and (Lc/W) magnification ratio, were introduced as input parameters (Root mean square error [RMSE]= 0.013 and R2 = 0.970 for the test stage). Nonetheless, sensitivity analysis showed that Froude number and head water ratio are the most influential parameters on discharge coefficients of the labyrinth and arced labyrinth weirs, respectively.

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One of the most effective ways to dissipate the destructive energy of water downstream of a flow control structure is the interference of water with air (such as a vertical drop). In this study, the hydraulic parameters of a vertical drop equipped with dual horizontal screens and with the subcritical upstream flow were investigated. Experiments were performed for two drop heights, two porosities, three relative distances between the screens, and a relative critical depth that was varied from 0.077 to 0.242. The results revealed that the relative distance between the screens does not affect the relative depth and downstream residual energy. On the other hand, increasing the relative length of the drop caused a decrease in the relative depth. Also, for a vertical drop equipped with a type 1 settling basin, the relative downstream depth decreased by more than 48%. The normal residual downstream energy and the relative total length of the drop are also decreased. The results also reveal that the use of dual horizontal screens transformed the regime of flow from super-to subcritical downstream of the drop.