植被作用下的弯曲复式河槽漫滩水流2维解析解

Analytical Models for Overbank Flows in Meandering Channels with Vegetated Floodplains

研究植被作用下的弯曲复式河槽流速分布对于确定其过流能力、泥沙输移、河床变形、滩岸保护有着十分重要的作用。作者研究了有植被的弯曲复式河槽中的垂线平均流速横向分布问题,在动量方程中加入滩地植被引起的拖曳力项,并考虑弯曲主槽和二次流的影响,采用3种不同的紊流扩散项积分方法,得到了3种计算模型。运用英国FCF弯曲复式河槽试验资料对模型进行验证,结果表明,在不同区域选取合适的二次流系数K比仅考虑主槽中的K值能更好地预测流速分布;滩地种植植物后,主槽中的K值明显增大;3种模型的预测结果在滩地上基本相同,主要差别出现在主槽区和掺混区。通过比较分析不同模型的计算误差,得到了计算结果最优的模型。

The velocity distribution in a meandering compound channel with vegetated floodplain was very important for determining sed- iment transport, channel process and bank protection. The lateral distribution of depth-averaged velocity in meandering vegetated com- pound channels was studied. For the streamwise momentum equation, the drag force due to vegetation was added to it as a momentum sink term. And three different integral forms of turbulent diffusion term were considered and three analytical solutions to depth-averaged velocity were obtained. The effects of sinuosity and secondary flows were also taken into account. The series of experimental data of UK-FCF were used to examine the three models, and the results indicated that using the optimum K values in each panel, the proposed model could predict velocity distribution better than the earlier method which ignored the secondary flow effects on floodplain. The K values in the main channel increased significantly after the floodplain was vegetated. The predictions of three models were almost the same on the floodplain and the differences were mainly in the main channel. On a whole, the model has the best agreement with experi- mental data.