Study On Unsteady Flow In Long -Distance Water Diversion Projects

Unsteady flow is usually called as hydraulic transients, which is an unstableprocess of flow and hydraulic pressure. Flow changing and hydraulic accident is thecommon causation lead to unsteady flow. In water diversion project, unsteady flowusually happened with flow changing, in which hydraulic pressure, water depth,discharge and velocity changed with time. Because unsteady flow is not adopted inthe design criterion, although it is critical with the safety of project, thus it became acommon issue argued and discussed by designer and operator. Lot of scientific studies made before is mainly on diversion pipeline ofhydropower station other than the characters of unsteady flow of water transportation.Considering the importance of interbasin water diversion project, the study ofunsteady flow of long-distance water diversion systems is not only an importantscientific research task, but also a has practical effects to design and operation ofwater diversion project. In view of the status of research in water diversion project, this thesis presenttheory of unsteady flow and devote effort to the studies on unsteady flow of waterdiversion projects. Studies have been made on some practical water diversion projects,such as Zhangjiuhe River Water Diversion and Water Supply Project, Water DiversionProject of Baixi Reservoir, Water Diversion Project of Luanhe River and Project ofTransferring Water from South to North in China. There are two common methods to study transient behavior in water diversionproject, which are hydraulic model experimentation and numerical simulation. It isdifficult to make a whole integrated model for a long-distance water diversion project,the metamorphic model can not achieve a accurate simulation, numerical simulation isthus a proper choice for study unsteady flow, although it has deficient to simulateindividual structure in detail. In order to get a better result, the thesis had studiedunsteady flow of water diversion project by numerical simulation couplingexperiment. The basic procedure is as follow: 1, getting datum of individual structureby hydraulic experiment, 2, cooperating the datum into the numerical model. The mathematical model and numerical method is the emphases of the thesis.Thus these methods are applied to practical issue. To the possible means of waterdiversion and they deferent hydraulic characters, kinds of water diversion project arestudied in this thesis, which include stepped low-pressure water diversion project,gravitational pressure conduit water diversion project and pumping pressure conduitwater diversion project. Based on the studies mentioned above, the numerical modelsof simulate transient characteristics for these projects are established. Computerprograms have been made in digital computation of unsteady flow. The results arehelpful to estimate the unsteady flow of water diversion project and some optimizedmethod to control waterhammer and oscillatory harm proposed for designer andoperator. Some achievement of the thesis is listed below:1. According to the hydraulic properties of low-pressure water diversion project, concept of stepped low-pressure water diversion project is defined and detailed. The numerical modeling established and program is made to simulate unsteady flow for these projects. Cooperating hydraulic oscillatory and hydraulic resonance into numerical simulation is our key emphasis in the study. By theoretical analysis and educe, the equation of oscillatory is proposed. Hydraulic natural frequencies are computed, which prove hydraulic resonance is exist indeed. The means to control oscillatory is suggested in the thesis. The suggested means is illustrated in the last program.2. Based some assumptive conditions, the mathematical model and computer program is established to simulate unsteady flow of unexpected accident. The conversion between free flow and pressure flow is simulated by digital method in this thesis. Hydraulic be...