Numerical Modelling Of Transition Between Free Surface And Pressurized Flows, And Transcritical Flow

Numerical modelling of one-dimensional unsteady flow in complicated systems, such as long distance water transfer project and urban storm sewer network etc., play a major role in practice of Hydraulic Engineering, in which transcritical flow and transition between free surface and pressurized flows are two important issues. In this thesis, an review on the research advance on the transcritical flow and free-surface-pressurized flow has been done. Based on the comparison of the common algorithms for one-dimensional unsteady flow, using this method in conjunction with the reduced momentum equation and the Preissmann Slot assumption, an mathematical model is established in the thesis. The numerical model is capable of handling both subcritical, supercritical and transcritical flow, free surface and surcharged flow.Extensive computations against analytical test cases or measured results have confirmed the validity of the numerical model, and the computational results with various computational parameters have been compared. Consequently, some conclusions on the modeling of transcritical flow and free-surface-pressurized flow has been obtained: using smaller slot width and smaller distance step , the computational results will be more accurate in modeling of free-surface-pressurized flow; using the method of reducing convective acceleration term in supercritical modelling, it is needed to supply uniform flow rating curve as downstream boundary condition etc..