When the gate of a high-head conduit is partly opened, negative pressure draws the air in through the air vent. Air that is entrained into the water is instantly forced downstream in the form of air bubbles. When studies on high-head gated conduits were examined, it was determined that the air demand ratio varied depending on many hydraulic and geometric parameters. This work has focused on determining the effect of conduit cross-section geometry on the air-demand ratio. A series of experiments were carried out on high-head radial gated conduits having different cross-section geometries. Experimental results showed that conduit cross-section geometry had an important effect on the air demand ratio especially in small gate opening rates. Further, design equations for the air demand ratio are presented relating the air demand ratio to Froude number, gate opening rate, and the ratio of gate opening to conduit length.

Fertigation involves dissolving fertilizer in irrigation water, and requires uniform water distribution and fertilization. A gated conduit can be used to inject liquid fertilizers or chemicals into a pressurized irrigation system. When the conduit gate is partially opened, a vacuum draws the fluid from the suction pipe into the conduit. An experimental study was conducted to investigate the fluid-injection ratio of gated conduits, which was shown to be high. The density and viscosity of the fluid were the most important parameters affecting the fluid-injection ratio. That ratio increased with increasing Froude number. It decreased as the gate opening proportion increased and with increasing conduit length. A design formula related to the Froude number, and the fluid's density and viscosity is presented to enable estimation of the fluid-injection ratio.

Gated conduits involve high-velocity air–water flow. When studies on gated conduits are examined, it is determined that the air-demand ratio changes according to the hydraulic and geometric parameters. However, no study has investigated the effect of the cross-sectional geometry of high-head conduits with a sluice gate on the air-demand ratio. In this study, the effect of conduit cross-sectional geometry on the air-demand ratio is examined. Results indicate that a conduit's cross-sectional geometry has an important effect on the air-demand ratio, especially at 10% and 15% gate opening rates. It is seen that the effect of the conduit geometry on the air-demand ratio decreases at 20%, and for greater gate opening rates. Moreover, a formula for estimated the air-demand ratio is presented, relating the air-demand ratio to the gate opening rate, Froude number, hydraulic radius and conduit length.

Accurate identification of flow regimes is crucial for understanding and analyzing flow behavior over stepped spillways. This study evaluates the ability of three machine learning regression models, namely AdaBoost Regressor (AdaBoost), Extra Trees Regressor (ETR), and Extreme Gradient Boosting (XGBoost), to predict three flow regimes (nappe flow, transition flow, and skimming flow) over stepped spillways. A dataset of 126 samples, including the ratio of critical flow depth to step height (hc/h), chute slope (α), and flow condition, was collected from a hydraulic experimental study. Two data splitting ratios were used for model training and testing: 110:16 and 84:42. The models were evaluated and compared using Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), coefficient of determination (R2), and Overall Index (OI). The findings revealed that AdaBoost, ETR, and XGBoost achieved higher accuracy than previous studies that employed Artificial Neural Networks (ANNs) and the Adaptive Neuro-Fuzzy Inference System (ANFIS), with R2 and OI exceeding 0.90 for both data-splitting ratios. The AdaBoost model demonstrated the highest performance, followed by ETR and XGBoost, respectively. This study contributes to the advancement of knowledge of machine learning models, particularly in their application to hydraulic engineering contexts.

Sluice and radial gates are common devices used to control flow in closed conduits. In high-head gated conduits, the high-velocity flow exiting the gate drags and entrains a lot of air. If the air demand of the flow is not met, the pressure drop downstream of the gate will cause structural damage or cavitation. Typically, an air vent is installed immediately downstream of the gate to supply sufficient air to the flow. In this study, the effect of the conduit gate type on the air-demand ratio was investigated. The results showed that the gate type had a very significant effect on the air-demand ratio. Significantly higher air-demand ratios were observed in the conduit with a sluice gate compared to the conduit with a radial gate. The results obtained will be useful in future modeling and design processes.