计入湿地植物影响的滇池二维流场计算

Calculation of two-dimensional wetland plant-impacted flow field in Dianchi lake

依据滇池生态环境建设规划,在以前研究工作的基础上,综合考虑湿地植物和湖泊水域条件变化,在水槽实验确定湿地植物综合糙率基础上,根据水动力学原理建立垂向平均化的二维水动力学模型。模拟研究了拆除防浪堤前后滇池水体及滇池生态湿地建成后湿地水体3种情况的流场,分析了湿地植物以及湖泊水体边界条件改变对滇池流场的影响。模拟计算结果表明,拆除防浪堤拓展水域对滇池湖泊流场整体影响不大,但拆除防浪堤改变了边界条件和风生流的局部流向,使滇池局部区域的流场变大。滇池北部福保和西山之间区域平均流速由0.73cm/s增加到1.18cm/s,增大了61.6%;滇池南端昆阳区域平均流速由0.34cm/s增加到0.57cm/s,增大了67.6%;其他区域的平均流速由1.22cm/s增加到1.32cm/s,增大了8.2%,变化较小。生态湿地建设对滇池流场的影响主要发生在湿地区域,湿地区域流场平均流速由0.43cm/s变为0.14cm/s,减少了67.4%;现有水体区域内流场平均流速由1.27cm/s变为1.21cm/s,减少4.7%,影响较小。研究成果对滇池湖泊生态环境的修复和建设有一定意义。

A depth-averaged 2D hydrodynamic model of ecosystem was developed in this work based on the comprehensive roughness of wetland determined by a flume experiment and some available information about Dianchi lake,such as the planning of ecological environment construction,the lake′s conditions of wetland plants and water area variation,and the previous studies.With this model,three types of flow fields were simulated to evaluate the effects of breakwater removing and ecological wetland construction and to analyze the flow field changes caused by wetland plants and different water boundaries.Results show that the breakwater removal for water area expansion produced little effect on the global water,but it caused significant changes in the local flow,due to its effects on the boundary location and the direction of wind-driven current.In the region between Fubao and Xishan of the north Dianchi,the average flow velocity was increased from 0.73cm/s to 1.18cm/s or by 61.6%,while in Kunyang of the south Dianchi,the velocity from 0.34cm/s to 0.57cm/s or by 67.6%.Velocity increase in the rest lake regions was quite small,from 1.22cm/s to 1.32cm/s or only by 8.2%.The impact of ecological wetland is limited within the wetland region of average flow velocity decreased by 67.4%（from 0.43cm/s to 0.14cm/s）,while this impact is little in the rest regions with only a 4.7% decrease in their flow velocity（from 1.27cm/s to 1.21cm/s） on average.These results are valuable to the ecological environment restoring and construction of Dianchi lake.