University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 49 1 2018 03 21 Experimental Studies of flow from Flap Gate in circular open channel at free flow condition Experimental Studies of flow from Flap Gate in circular open channel at free flow condition 159 170 65581 10.22059/ijswr.2018.231957.667672 FA Babak Mahmoudi Department of Water Engineering, Faculty of Agriculture, Urmia university, Urmia, Iran 0009-0002-3557-0903 Javad Farhoudi Irrigation and Reclamation Department, University of Tehran, Alborz, Iran 0000-0002-4839-223x Journal Article 2017 04 25 Present research covers the results of a theoretical and experimental investigation on a circular and quadratic flap gate, which installed at the exit of a circular channel. This study would employ an experimental program in a horizontal channel of circular cross section of 200 and 300 mm diameters, equipped with either a circular or quadratic flap gate to explore the basic parameters affecting the flow discharge estimation of these devices. In this study, of three ways such of the first form Stage-Discharge technique, incomplete self-similarity theory and the second form Stage-Discharge technique have been used for estimating the discharge for circular and quadratic flap gate under free flow conditions. The research took the advantages the main difficulties during the experiments were the vibration of the gate as well as accurate measurement of gate opening. The use of second form Stage-Discharge technique would overcome such weaknesses. The most accurate of these methods is incomplete self-similarity theory. In this theory, mean absolute relative error for circular flap gate is equal to 3.34% and for 4.1% for quadratic flap gate. Present research covers the results of a theoretical and experimental investigation on a circular and quadratic flap gate, which installed at the exit of a circular channel. This study would employ an experimental program in a horizontal channel of circular cross section of 200 and 300 mm diameters, equipped with either a circular or quadratic flap gate to explore the basic parameters affecting the flow discharge estimation of these devices. In this study, of three ways such of the first form Stage-Discharge technique, incomplete self-similarity theory and the second form Stage-Discharge technique have been used for estimating the discharge for circular and quadratic flap gate under free flow conditions. The research took the advantages the main difficulties during the experiments were the vibration of the gate as well as accurate measurement of gate opening. The use of second form Stage-Discharge technique would overcome such weaknesses. The most accurate of these methods is incomplete self-similarity theory. In this theory, mean absolute relative error for circular flap gate is equal to 3.34% and for 4.1% for quadratic flap gate. https://ijswr.ut.ac.ir/article_65581_54078928d109ff10b9dd8cd2ae274ecf.pdf