Research On The Hydraulic Characteristics Of The Vortex Before The Partially Opened Radial Gate

Previous studies of vortex problem in hydraulic engineering are mainly focused on the spillway tunnel and the power station and other intakes, which have the constant inlet structure and deep submergence. The studies of the vortex problem in front of the partially opened gate are few, which will also cause serious hazards to hydraulic structures, such as induce vibration of the gates or other structures, reduce the discharge, cause cavitation of the discharge side, and so on. To avoid or control the vortex hazards in front of the partially opened gate, in this paper, the characteristics of the vortex flow field and the vortex in front of the partially opened gate were studied systematically with the methods of theoretical analysis and experimental research. The main research contents and conclusions are as follows:(1) In this paper, the vortex flow field was detailedly measured by the particle image velocimetry technology (PIV) in the vortex tank experiment. The radial and tangential velocity distributions, vortex core radius variation, water surface profile and circulation distributions have been obtained, which have revealed the variation tendency of the vortex hydraulic parameters. Based on the theoretical analysis and experimental data, a mathematical model describing the key vortex characteristics was established. The comparison with the previous models and experimental data shows that the model established in this paper have higher precision, simple form and are easy to use.(2) To research the vortex characteristics in front of the partially opened radial gate, a sluice project was taken as the research object. And the formation mechanism, influence factors, critical submergence and other characteristics of the vortex have been studied by two contrast model experiments of different scale. The research results show that the formation of the vortex in front of the gate is the result of the combined action of intake Froude number and the progressive flow circulation. The factors influencing on the vortex in front of the gate include the submergence of the intake, the gate opening, the intake Froude number and the progressive flow circulation. The critical submergence of the vortex in front of the partially opened gate has two limitations. When the submergence of the intake is between the two critical submergence limitations, there will be air-core vortex occuring. In addition, the circulation effect of the progressive flow is weak near the lower limit of the critical submergence, in contrast, the circulation effect is obvious near the upper limit of the critical submergence. When the gate opening and the inlet Froude are greater, the air-core vortex is stronger.(3) The mechanism and influence of the viscous force and surface tension on the vortex were studied in this paper through the theoretical analysis and experimental data analysis. The result shows that in the experiment designed according to the gravity similarity criterion, the influence of viscous force and surface tension on modeling vortex in front of the gate can be ignored when the Reynolds number Re?5.1×104, and Weber number We ?142. And the lower and the upper critical submergences were derived by mathematical model established in this paper. The comparison of the critical submergence formulas with the experimental data of this article or previous proofs that the formulas not only applied to calculate the critical submergence of the vortex before the radial gate, but also are suitable for both the structure unchanged side intake or vertical intake and so on.(4) To eliminate the air-core vortices in front of the partially opened gate, the vertical anti-vortex barrier was proposed in this paper on the basis of the vortex characteristics analysis and the existing anti-vortex structures summarize. The experimental results show that the two pairs of anti-vortex barrier plan works well, which can meet the requirement of eliminate vortex.In conclusion, the characteristics of the vortex flow field, the formation and development mechanism, the critical submergence, anti-vortex method and other issues of the vortex before the gate were systematically studied in this paper. The research results in this paper can provide data and theoretical basis for the further research or references for engineering design and operation.