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Offshore wind power plant, having the fine development prospect as one kind of preponderant generate electricity way because of few field, no pollution, regeneration. But arranging of the generator group in open sea, certainly affects ambient condition of the streams and silt. Therefore, on the condition of the numerical modeling of tidal current exist the pier, it is necessary to think the effect of the piers.As a case study of Shanghai Offshore wind power plant, based on the finite element method, build a 2-D tidal current numerical modeling of wind power generate electricity factory covered with Yangtze Estuary and Hangzhou Bay and adjacent sea area . Making use of the technique of grid nesting, simulating the dimension of pier accurately, Overcoming the difficulty that in the large-scale sea area simulates small dimension of piles group, and analyzing the effect of flowfield as the arrangements of the piers. The result shows that:(1) The range of effect has very close relation with the arrangement.On the condition of the same cross-section, as Fengxian plant, the arrangement that along the flow , longer with the length of the piers is increased, the pier influences each other, and create the phenomenon of covering- stream perhaps, the range of effect and degree is large; as East China Bridge-one, the arrangement that across the flow, the effect is similar to the single pier, the range of effect and degree is smaller.On the condition of the same arrangement, as East China Bridge-two,three,four, more the piers along flow direction are, bigger the dimension is, the range of effect is larger, and that the difference is more obviously with the distance is closer to the pier.(2) The calculation results show that the ambient flow field of the pile is affected obviously by the value of horizontal eddy viscosity coefficient. The area of flow field, the tidal level, the mean velocity are enlarged with the increase of the horizontal eddy viscosity coefficient, and closer the pile is , the change of tidal level and mean velocity are larger; Analyzing the rationality of horizontal eddy viscosity coefficient from two aspects which are the phenomena of water bypassing and the maximum flood of the piers, and it is reasonable if the value equals to 1000m~2/s.
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