| Vortex often occur in front of the intake of hydraulic structures.If intake funnel vortex occurs before the inlet,it will deteriorate the inlet flow,reduce the discharge capacity of the inlet,increase water pulsation,cause the building's vibration,and so on.The study of the influencing factors of vortex at hydraulic intakes is the basis of the research on the actual vortex problem in almost all engineering.Predecessors'research on vortex are mainly for the diversion tunnel inlet of flood discharge tunnel,the intake of power stations,etc.However,there are few researches on vortex characteristics before gate opening when the gate is partially opened.In recent years,there are many researches on the vortex elimination methods of some projects,but few on the influencing factors of vortex.To avoid the occurrence of harmful vortex or reduce the harm of vortex and ensure the safe operation of hydraulic engineering,it is necessary to study the influencing factors of intake vortex before gate.In order to study the influential factors of the air-core vortex occurs in front of the gate caused by partial opening of radial gate,the relevant experimental study and theoretical analysis are made with large scale hydraulic model by taking one of the orifices of a sluice gate as the study objective.The main contents of this thesis are listed as follows:(1)The paper describes the classification of vortex and its harm,reviews the current research situation of vortex at home and abroad from theoretical research,experimental research and numerical simulation.The significance of the research on the influencing factors of vortex before sluice is illustrated.(2)The paper introduces some basic theories of fluid motion and vortex,including the basic concepts of vortex,the basic equations of vortex movement.The basic analytic solutions of vortex under various boundary conditions and initial conditions are introduced emphatically.(3)Based on a flood sluice project,according to the Froude number similarity criterion,a large scale model is used to study the model test.The test range is determined,and the test instrument and measurement method are introduced.The various hydraulic factors before the gate are measured,including the flow pattern of the water in front of the gate when the gate is open,the discharge capacity,the depth of water in front of the gate and the flow velocity in front of the gate.(4)The influencing factors of gate vortex before and after bulkhead gate and radical gate are mainly studied.The study shows that the factors that influence suction vortex include mainly:the water depth of the radical gate,the gate opening,the circulation,the viscous force and the surface tension.Through experimental observation and theoretical analysis,we come to the conclusion that the vortex in front of gate exists the upper and lower two critical submergence depths.When the water depth in front of the gate is between the two critical submergence limitations,there will be air-core vortex occurring.When the gate opening is greater,the aspect ratio of the inlet gate is smaller,and the air-core vortex is stronger.When the circulation effect of the incoming boundary condition is more obvious,the air-core vortex is stronger.The effects of viscous force and surface tension on bulkhead gate model experiment can be ignored when the Weber number We?(83-228),and the Reynolds number Re?4.4×10~4.The effects of viscous force and surface tension on radial gate model experiment can be ignored when the Weber number We?(104-208),and the Reynolds number Re?4.4×10~4.Finally,by theoretical analysis,a critical submergence formula which has considered the effects of gate opening and circulation is established in this paper.In this paper,the study on influential factors of vortex in front of gate are analyzed by the relevant experimental and theoretical.It can be for vortex theory and vortex elimination measures provide a certain basis.As well as it can be for practical engineering design and operation management to provide certain reference. |
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