عنوان

بررسی اثر تیغه منحرف کننده جریان بر خصوصیات هیدرولیکی سر سریز-دریچه استوانه ای,S

Weirs, are used for measuring the flow in open channels. These weirs, with respect to the required accuracy and the circumstances which they are used in, have different sections. Cylindrical weirs are cheaper and their construction is easy compared to other weirs such as triangular and rectangular weirs, and as a result of their design they have a high flow rate. In this research, the effect of a deflector on the hydraulic characteristics of the flow in a cylindrical weir- gate with a constant diameter but varying dimensions are studied. In this study the main parameters that are affecting the discharge coefficient of flow (Cd) have been experimentally investigated. These parameters, have been found to be dimensionless and their respectful functions were setup using the Buckingham ? theorem. The experiments were carried out in a rectangular flume with a length of 11 m, a width of 30 cm, and a depth of 70 cm on a flat and rigid bed with a constant slope in the laboratory of hydraulics. The physical model of the cylindrical weir- gate was made by plastic pipe with a diameter of 110 mm. The experiments were conducted with the gate openings being on three different heights from 22 to 66 mm by moving the structure perpendicular to the direction of the flow, and by utilizing three widths and angles of the deflector for 10 discharges. The ratio of the diameter of the structure to the width of the channel was 0.33 units. The tests were done in free flow conditions. The Froude and Reynolds numbers of the input flow is in the range of 0.17 >Frup > 0.27 and 5500< Reup< 12000 respectively so the flow was turbulent and subcritical. Studying the discharge verses head in this research shows that, the discharge of flow has a direct relationship to changes in water level. According to the results, in all of the experiments, with increases in the gate openings, the discharge coefficient is inversely ??. The discharge coefficient of the cylindrical weir-gate decreased with the increase of flow rate and decreased with an increase to the opening of the gate. Also the change in the discharge coefficient has a decreasing relationship with the angle of the deflector. Since the deflector is installed at the downstream side of the structure, the head loss due to conjunction the flow over the weir with the flow under the gate was decreased. The discharge coefficient was more when the deflector was installed compared to when the deflector was removed. With an increase in the gate opening, the values of Hw/H, H/P, H/Htw decreased and this decrease was caused by an increase of the flow rate. With increasing the length of the deflector, the values of Hw/H, H/P, H/Htw increased, which compared to the deflector-less state was more. With an increase in the angle of the deflector, Frup had a slight decrease and with an increase in the length of the deflector, Frup stays the same and when compared to the reflector-less state, they are approximately the same