The discharge characteristics of flow over and under different weir-gate structures were investigated using dimensional analysis and multivariable regression techniques. Based on the shape and geometry of weir-gates, seven weir-gate structures were classified. The interaction factor, defined as the ratio of the measured discharge over and under the weir-gate structure to the sum of the predicted weir and gate discharges from the literature, was calculated for all types of weir-gate models. Six weir-gate models were experimentally tested to study the discharge characteristics of flow over weirs of finite crest length and under gate. The interaction factors were correlated with the geometry parameters for all weir-gate models with an average coefficient of determination of 0.85. A series of regime plots was developed to assist designing the weir-gate structures as flow distributors for a sharp-crested weir-gate and a weir of finite crest length with an offset. The regime plots show the contribution of weir and gate discharges for different weir-gate geometries. A critical normalized head was introduced as the flow through the weir-gate structure is equally divided by the weir and gate. Based on the weir-gate geometry and discharge, general empirical equations were developed to estimate the critical normalized head for practical engineering applications.

Abutment scour is a complex three-dimensional phenomenon, which is one of the leading causes of marine structure damage. Structural integrity is potentially attainable through the precise estimation of local scour depth. Due to the high complexity of scouring hydrodynamics, existing regression-based relations cannot make accurate predictions. Therefore, this study presented a novel expansion of extreme learning machines (ELM) to predict abutment scour depth (d_s) in clear water conditions. The model was built using the relative flow depth (h/L), excess abutment Froude number (F_e), abutment shape factor (K_s), and relative sediment size (d₅₀/L). A wide range of experimental samples was collected from the literature, and data was utilized to develop the ELM model. The ELM model reliability was evaluated based on the estimation results and several statistical indices. According to the results, the sigmoid activation function (correlation coefficient, R = 0.97; root mean square error, RMSE = 0.162; mean absolute percentage error, MAPE = 7.69; and scatter index, SI = 0.088) performed the best compared with the hard limit, triangular bias, radial basis, and sine activation functions. Eleven input combinations were considered to investigate the impact of each dimensionless variable on the abutment scour depth. It was found that d_s/L = f (F_e, h/L, d₅₀/L, K_s) was the best ELM model, indicating that the dimensional analysis of the original data properly reflected the underlying physics of the problem. Also, the absence of one variable from this input combination resulted in a significant accuracy reduction. The results also demonstrated that the proposed ELM model significantly outperformed the regression-based equations derived from the literature. The ELM model presented a fundamental equation for abutment scours depth prediction. Based on the simulation results, it appeared the ELM model could be used effectively in practical engineering applications of predicting abutment scour depth. The estimated uncertainty of the developed ELM model was calculated and compared with the conventional and artificial intelligence-based models. The lowest uncertainty with a value of ±0.026 was found in the proposed model in comparison with ±0.50 as the best uncertainty of the other models.

Laboratory experiments were carried out to investigate the water surface characteristics of submerged flow over sharp-crested weirs. Interesting observations were made on the water surface profiles near the weir as weir submergence sets in as well as for various stages of submergence. Submerged flow was divided into four regimes: (I) impinging jet, (II) surface jump, (III) surface wave, and (IV) surface jet. It was found that a surface jump turned into a surface wave when the wave trough became level with the tip of the weir. The surface jet regime began as the surface waves faded out. A condition was set to quantify the boundary between the surface wave and surface jet regimes. Based on flow observations, the surface jet regime sets in as the amplitude of the surface wave becomes small (i.e., less than 0.1h, where h is the head). An empirical equation was developed based on the literature data to predict the discharge reduction factor in the generally used discharge equation. This formulation was...

Laboratory tests were carried out to investigate the hydraulics of submerged flow over triangular weirs and weirs of finite-crest length with upstream and/or downstream ramp(s). Water surface profiles were recorded as the weir submergence set and for various stages of submergence. Variations in modular limit and discharge reduction factors for the present weirs were studied. It was found that the modular limit varied with the ratio of the free-flow head to the total streamwise length of the weir. Characteristic length scales such as horizontal and vertical distances from the toe of the surface jump and the first wave trough to the downstream crest edge of the weir were measured to generalize different wave patterns. It was found that the toe of the surface jump moved toward the weir as the weir submerged and varied linearly with the submergence level, which is the ratio of tailwater to headwater depths. For weirs of finite-crest length with upstream and downstream ramps (i.e., embankment weirs), the toe of the surface jump moved toward the weir as the submergence level increased up to 0.7. For higher submergence levels, the trough of the surface wave moved toward the downstream and eventually washed away. Efficiency and performance of the present weirs were evaluated with their own free-flow conditions. Empirical formulations were developed to predict the discharge reduction factor with submergence level. The performance of triangular weirs in submerged-flow conditions was found to be better than that of corresponding sharp-crested weirs; weirs became more efficient as the ratio of the free-flow head and the total length of the weir increased.