Three-dimensional analysis of flow and contaminant transport near the dam of hydropower station

Velocity distribution along traverse and vertical directions of flow near the dam of a hydropower station is non-uniform due to irregular geometry boundaries. Outlets located on the dam strengthen the three-dimensional property of flow. For this reason the concentration distribution of contaminant is also three-dimensional. The outflow water qualities obtained from the vertical two-dimensional models are inaccurate as a result. Three-dimensional numerical solutions of flow, BOD and DO concentrations of a reservoir reach near the dam of a hydropower station are carried out and numerical results are presented in this paper. Numerical solution is based on CFX, a commercial CFD code developed by AEA Technology plc. In the simulation, the k- epsilon model is chosen and finite-volume method is adopted to the discretisation of model equations under boundary-fitted coordinates. The finite difference equations are solved by coupling algorithm. Analysis to the numerical results shows that local geometry and outlet locations near the dam affect the flow structure strongly. Due to their effects, the outflow water qualities do not correspond to the numerical results by corresponding elevations of one or two-dimensional models. It can be concluded that numerical results presented in this paper reveal the main properties of flow and contaminant transport in the computational area. Up to now, reports on three-dimensional numerical simulation to a large-scale computational domain with irregular geometry can rarely be found.