Discharge Coefficient of Combined Orifice-Weir Flow

Combined orifice-weir flow is a complex phenomenon in hydropower and the discharge capacity of a structure affects the safety of the structure. It is essential to propose an equation for computing the discharge coefficient of combined orifice-weir flow. Based on theoretical analyses and physical experiments, 284 laboratory tests were performed to determine the discharge coefficient. The parameters affecting the discharge coefficient were determined and the relationships between the coefficient and four parameters, that is, the ratio of the water head to the upstream water level, the ratio of orifice height to orifice-weir height, the ratio of orifice height to the water head, and the ratio of the length to the height of the orifice-weir structure, were established. According to the dimensional analysis and the linear-fitting method of multidimensional ordinary least squares, five models were constructed to analyze the sensitivity of the model’s accuracy by using different parameters. The sensitivity to each parameter was also evaluated. The results were examined with statistical indices and they showed that one model yielded the best results, which were consistent with the experimental values. Thus, the proposed model is effective in estimating the discharge coefficient of combined orifice-weir flow.