Study On Hydraulic Characteristics Of The Gate Inclined To Horizontal Position After Falling

Based on the analysis of investigation on hydraulic characteristics of gate in recent years, the research on hydraulic of the gate inclined to horizontal position after falling was carried out with theoretic analysis, physical model and numerical model.Through dimension analysis, conclusions was drawn that the discharge coefficient of the gate was affected by the Reynolds number, the angle of gate opening, the relative length of the gate and the degree of submergence. The volume of aeration was affected by the Froude number and the height of the cavity pocket at the back of the gate.Through physical model experimentation, the discharge capacity, the distribution of time-average pressure intensity, the characteristic of fluctuating pressure intensity and the volume of aeration were researched. The discharge coefficient was affected by the angle of gate opening at the free discharge. When the angle of gate opening is about 30°, the discharge coefficient had the maximum. The discharge coefficient decreased as the relative degree of submergence increased at the submerged discharge. The dynamic pressure distribution on the gate was different from the hydrostatic pressure distribution. The dynamic pressure was negative at the top of upper gate. It was smooth that the signal of the fluctuating pressure intensity. The distribution of the signal amplitude was close to normal distribution at test conditions. The fluctuating pressure intensity at the downward side of the gate increased 8% due to the invalid of aeration. The results of the chart of frequency analysis indicated that the frequency structure of fluctuating pressure intensity was similar and the fluctuating pressure intensity was low-lying frequency. At different opening angles of gate, the air-water ratio increased as the Froude number and the height of cavity after gateincreased.Through numerical modeling, the flow pattern over gate and the time-average pressure intensity at the gate were analyzed. At the free discharge, the water nappe trajectory distance changed as the angle of gate opening. It was shorter at the 90° of the gate opening. The vortex of water behind the gate increased first and then decreased as the angle of gate opening increased. When the angle of gate opening unchanged, the vortex after the gate increased and there were evident hydraulic jump as the water level of the downriver increased. When the aeration failed, the flow over the gate was attached to the back of the gate, the flow velocity decreased. The numerical results of time-average pressure intensity on gate were close to that of experiment.