丹巴水电站上游河道岸坡对截流龙口水力参数的影响分析

Influence Analysis of Upstream River Banks on the Hydraulic Characteristics of Closure Gap for Danba Hydropower Station

对丹巴水电站截流模型采用数值计算,求解沿程水面线和平均流速,分析由上游边坡导致龙口前水流流向和水面宽度的改变对截流的影响。计算结果表明:龙口前水面宽度的改变使河道出现双龙口截流,产生双龙口效应,减小了龙口截流水力要素,但加深水流对河床和坡脚的冲刷;水流流向的改变使河道出现堤头挑流,龙口产生边界层分离现象,减少了堤头抛投量,但加重主流对基坑和岸坡的冲刷。

A numerical simulation model is built to study the fiver closure of Danba Hydropower Station. The water surface line and average velocity along flow route are obtained, and the influences of the changes of water surface width and flow direction ahead of closure gap caused by upstream fiver banks on fiver closure are analyzed. The results indicate that, （a）The effect of double closure gaps is generated by the change of water surface width, which decreases the magnitude of hydraulic parameters of closure gap, but increase the scouring along fiver bed and dike feet; and （b）The stream is deflected beside the pier head and the phenomenon of boundary layer separation is generated due to the change of flow direction, which can decrease dumping intensity, but increase the scouring by main stream along the foundation and fiver banks.