Extraction of flow Rate Equation under Submerged Flow Condition and Determining of Related Coefficients in Pivot Weirs with the Different Side Contractions

Pivot weirs are used in irrigation networks in order to regulate water surface elevation and flow measurements. Few studies have been reported on head-discharge relation of mentioned structure under submerged flow condition. In this study, one equation based on energy and critical depth equations is proposed to determine discharge equation. To determine the coefficients of these equations, measured data in an experimental model on the three pivot weirs with different three side contractions compiled with the USBR (United States Bureau of Reclamation) experimental data of data, the discharge coefficient was estimated for and submerged flow condition . Comparisons of experimental results with presented relation indicatest he range of error for the proposed equation was less than ±20% , where the submergence factor was between 0.2 and 0.9 , which in comparison to Brater and King’ relation with ±40% error has a good accuracy.