7. Prediction of Discharge Coefficient for Side Rectangular Weir Using Group Method of Data Handling (GMDH)

A side rectangular weir is used as a flow diversion structure, having spatially varied flow with decreasing discharge. They have various applications in the field of river, hydraulic, environmental and irrigation engineering. In this study, group method of data handling (GMDH) with two types of transfer function, namely quadratic polynomial one variable and quadratic polynomial two variable, were used to estimate the coefficient of discharge for sharp-crested side rectangular weir. On the basis of the F-test, it is found that the upstream Froude number is the most influencing parameter for the estimation of the coefficient of discharge. On the basis of dimensional analysis, it is observed that the coefficient of discharge depends on the ratio of the crest height to the length (P/L), ratio of breadth of the main channel to length (B/L), approach flow Froude number (F₁) and ratio of the upstream depth to length (y₁/L) of sharp-crested side rectangular weir. The coefficient of correlation (R = 0.93), average absolute deviation (AAD = 2.99) and mean absolute percentage error (MAPE = 3.078) show better performance of the present GMDH model. Finally, the results indicated that the GMDH model could provide more accurate predictions than those obtained by traditional regression models.