吞吐流量对湖泊流场结构影响的数值试验

本文利用EcoTaihu三维生态模型中的三维水动力学模型,开展了典型背景风场、多个吞吐流量条件下的湖流数值试验,分析比较流场达到稳定状态时。沿垂直方向平均流场随吞吐流量大小的变化特征。结果表明:随着吞吐流量的增加,湖泊垂向平均流场逐渐由受风生流控制转变成受吞吐流场控制,在此转变过程中存在临界吞吐流量值。当吞吐流量大小超过该值时,流场结构发生明显的改变,湖泊内小尺度的环流先消失,规模最大的环流最后消失;环流中流向和吞吐流流向一致的区域流速得到加强.而与吞吐流流向相反或差异较大的区域.流速先减小,后增加。风向和风速是影响临界吞吐流量值大小的主要因素。本文的研究结果对认识湖泊流场特征和了解物质在湖泊内的输移扩散具有重要意义,为合理规划引调水、准确预测水质、重建健康生态湖泊提供基础科学依据。

NUMERICAL EXPERIMENTS ON THE INFLUENCES OF INLET AND OUTLET FLOW ON LAKE CURRENT

Numerical experiments on the influences of inlet and outlet flow on lake current was conducted by means of the 3-D hydrodynamic sub-model of EcoTaihu Model on a man-made Lake Zhuhu.It is concluded that the inlet and outlet flow has little influence on the vertical- averaged lake water current when the retention time of water in the lake is longer and it could only change the water current structure in estuary of inlet and outlet.By contraries,it shows great influences on the current and may change the whole lake water current pattern especially when it is big enough and gets to some important value.For example it may induce the wind-driven circumfluences in the lake to disappear when it increases to some critical val- ue.During the process that the circumfluences disappear,it has positive effect on the speed of the water current at the site where wind-driven current is in the same direction as the inlet and outlet driven current,and negative effect on the water current at the site where wind- driven current direction is opposite to that of the inlet and outlet driven current.The water current speeds at the sites become smaller and smaller.It may increase after it becomes 0 cm/s.The inlet and outlet flow will be involved as wind and topography,when the current characters and transportation and diffusion of substance are detected in lake,especially in the lake with short water retention time such as man-made lake.