| Nowadays many great hydro-power stations, which are being built or will be built in our country, mainly locate on trunk stream of great rivers and most of these rivers mustbe open to navigation. Consequently, research works must be done not only on stability of cofferdam feet, channel scour, protection of the bank and so on, but also on navigation problems and salvation of downstream river during river diversion construction. In order to solve the problems of navigation and salvation during river diversion construction, further research on velocity field and water surface profile in length and breadth should be done. However, such research works can't be done by traditional hydraulics of river diversion. So the numerical simulation of the river flow field is adopted and introduced in this thesis.The basic equation of the Finite Volume Method (FVM) is obtained using the divergence theorem after being integrated. In FVM the unstructured or structured meshes are used to represent the computational domain. Firstly, the mass and momentum fluxes through each mesh are calculated according to the balance theory. Then the water elevation and depth-averaged velocity of each mesh are obtained at the end of each interval. Two-dimensional unsteady flow model, RBFVM-2D, is based on the finite volume method. One of the attractive features of this model is to treat the calculation of the mass and momentum flux across each side of elements as a local Riemann problem that is solved using the flux vector splitting scheme (FVS). In this thesis, the Finite Volume Method (FVM) is adopted to simulate two-dimensional river flow field during diversion construction and the first construction period of diversion project of Xiangjiaba is cited to verify correctness of computing method of flow field and validity of river diversion application. Furthermore, computation results accord with the physical model experiment results on the spot.
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