| Abstract: | A side orifice is an important type of hydraulic structure which is used widely in irrigation and waste management systems to divert desired discharges from a main channel or to distribute the flow within the basins. Circular pipes flowing partially full are often used in these systems, but existing predictive relations developed for rectangular channels result in significant error. In the present study, the flow through a side orifice in a circular open-channel is numerically simulated and validated to test the effect of different parameters on the discharge coefficient and propose an appropriate predictive equation. To minimize the number of required simulations and validations, a Response Surface Method-Central Composite Design (RSM-CCD) is employed. Results showed that the discharge coefficient is inversely related to the Froude number (Fr) and the ratio of the side orifice length to the approaching flow water depth. However, any increase in either the ratio of the orifice length to the main channel diameter or the ratio of the lower crest level to the orifice length will increase the discharge coefficient. A new equation is presented to determine the discharge coefficient of side orifice in a circular open-channel using RSM-CCD. The sensitivity analysis showed that all linear terms must considered in the equation but that the interaction terms can be dropped. The maximum error of the equation to predict the training and validation data are 1% and 2% respectively. |
