Experimental investigation on cylindrical weir- gate location in perpendicular orientation to flow direction on discharge coefficient

Cylindrical weirs- gates are one of the combined structures types which have advantages such as lower cost, simple design, easy construction and the high discharge coefficient. In current study, the cylindrical weir- gate location in perpendicular orientation to flow direction on discharge coefficient have been investigated experimentally. The experiments were conducted in a flume with the length of 7.5 m and width of 40 cm, using the cylindrical models were made up of plastic pipes with diameters of 50, 75, 110 and 125 mm. Experiments were conducted with different gate opening heights from 0 to 60 mm (reaching to the cylindrical gate by considering the available diameter and discharge). The results show that the maximum and minimum discharge coefficient has been observed respectively, in the cylindrical weir and cylindrical gate. Moreover, by converting the structure from cylindrical weir- gate to cylindrical gate, the curves depicted amount of Cds against the ratio of upstream flow depth to cylinder diameter (yup/D) and the ratio of difference between upstream and downstream flow depth to cylinder diameter ((yup-yd)/D) have reduced suddenly, which this progress was due to decreasing the amount of back water and remarkable decreasing in upstream depth. Furthermore, increasing in amount of cylindrical structure diameter leads to discharge coefficient amount decrease. The best correlated relations for quantifying the behavior of discharge coefficient Cd, were proposed.