Numerical Computation And Study On Hydraulic Characteristics Of Transients Process In Long Distance Water Transfer System

In long distance water transfer system, the condition of steady flow is destroyedby the flow rate regulation and hydraulic accident, and then the unsteady flow occurs,which is called as hydraulic transient process. The hydraulic parameters in thetransient process will change quickly with time and usually overstep the design valueof steady flow, which will cause a negative effect on the system. So researches on thehydraulic transient process is necessary to design and operation of the water transfersystem. Based on the former theories, the thesis devotes effort to the studies on severaluniversal problems about hydraulic transients process and draw some conclusions.Then numerical computation is applied in a practical water diversion projects. Whileseeking for the uniform solution to hydraulic transients process, the thesis also bringsforward corresponding proofs and suggestions for project design. The researchesmade by this thesis include several aspects as below. 1. The water hammer wave speed of the two-phase flow is analyzed in this aspect.Pearsall's alterable wave speed formula has been introduced in the characteristicsmethod. Then the transient flow in pipe systems is computed with the method ofinterpolation characteristics. The Influence of hypersensitive factors, such as headpressure,pipe characteristics, on the change of the water hammer wave speed in thetwo-phase flow is studied. On the basis of data analysis, the thesis draws theconclusion that the decline of head pressure and the increase of the relative thicknessof pipe and Young's modulus of material all can enforce the change of the waterhammer wave speed. The bias arised in the process of computation is analysied in theend of this chapter.2. In view of the continuous change of flow pattern in pipe transient process,basing on analyzing the flow pattern, coefficient of friction resistance is computed.Thus the precision of computation can be improved.3. For the most complicated water transfer system, the Preissman's method isapplied in the compuation process of the transient process of pressure pipe-openchannel system. Because of the great difference between the water hammer wavespeed and water surface wave speed, different dimensional step is applied to pressurepipe and open channel respectively and a applicable method about how to choose timestep is put forward. Founded on the analysis of the transient process model ofpractical project, the mathematic model is proved to be feasible and suggestions aremade out for the design and operation of pratical project.