Discharge Characteristics of Weir-Orifice and Weir-Gate Structures

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.