杭州西湖三维流场特性的现场观测及模拟研究

Field observation and simulation study of three-dimensional flows in West Lake,Hangzhou

采用浮标下挂ADCP仪方法,开展了西湖分层流场的现场观测,首次通过实测资料证实了西湖垂向环流的存在。采用EFDC模型对实测风场作用下的西湖分层流场进行了数值模拟,垂向流速分布特性的模拟结果与实测结果符合较好,表明该模型可以适用于西湖流场的数值模拟。在2013年西湖实测风场分析的基础上,对比分析了常风向东北风与西南风作用下的西湖分层流场特性,结果显示风场是影响西湖流场的敏感因素,尤其对表层流场作用明显。受风场作用,东北风条件下在外湖湖心与东南近岸水域存在顺时针环流,西南风条件下在外湖湖心与东南近岸水域存在逆时针环流。湖区流速为mm/s^cm/s,且分布不均匀,其中进、出水口及近岸水域流速相对较大,湖心流速较小。

Field observation of the stratified flows in West Lake was carried out in this study using a buoy-up ADCP meter method, and flow circulations in this lake were detected and confirmed for the first time. The flows were also simulated using an EFDC model and the in-situ measured data of wind field. The simulations were in good agreement with the layered velocity measurements of the flows, and it showed a good applicability of this model to the lake＇s stratified flows. We analyzed and compared the characteristics of stratified flows under constant northeast wind and southwest wind across the lake measured in 2013, and found out that the flows in the lake, especially in its surface layer, were very sensitive to the wind field over it. A clockwise circulation was often formed at its southeast side under northeast wind, while an anticlockwise circulation at nearly the same location under southwest wind. Flow velocities in the lake varied from the order of 1 mm/s to 1 cm/s, uneven in distribution; higher velocities were around its inlet and outlet and near its bank while lower velocities in its central part.