微弯河岸沿线扰动压强分布特性试验

Laboratory experiments on pressure distribution along sinuous riverbanks

河岸沿线的压强梯度是河岸侧向潜流交换及河岸带物质和能量传递的主要驱动力。为揭示微弯河岸边界的扰动压强分布规律和主要影响因素,利用室内变坡水槽系统,制作不同体形的正弦形河道模型,实测一个周期波长的河岸表面压强水头,研究河岸不同分层、不同弯曲程度和不同水流条件下的沿线压强分布特性,并进行影响因素的敏感性分析。试验结果表明,在缓流条件下正弦形微弯河岸的沿线扰动压强分布呈曲线形波动,不同分层的压强分布规律大体相同。在河岸弯曲程度较小时,压强波动的峰值与谷值分别出现于凹岸和凸岸的曲率最大位置。河岸沿线扰动压强的变化主要受河岸振幅与波长比a/λ和来流弗劳德数Fr的影响,敏感性分析表明a/λ比Fr的影响更为显著。

The pressure gradient along riverbanks is one of the main driving forces for lateral hyporheic exchange, substance and energy transport in riparian zones. In order to reveal the discipline and main factors of disturbed pres- sure distribution along sinuous riverbanks, series of experiments are carried out in an adjustable slope test flume. Dif- ferent geometries of sine-shaped channel models are built and put into the flume to form different boundaries of river- banks. The pressure head data are measured in a wavelength range of riverbanks to study the characteristics of pres- sure distributions in different layers, different sinuosity of riverbanks and different hydraulic conditions. A sensitivity analysis of influence factors is also conducted. The experimental results show that the pressure distribution along the sinusoidal riverbank is a curved shape. The pressure distributions in different layers are almost the same. When the ri- verbank sinuosity is relative low, the pressure variation reaches the crest value and trough value respectively at the most concave and convex location of riverbanks. Under subcritical conditions, the disturbed pressure along the river- bank is mainly affected by the bank amplitude-to-wavelength ratio a/A and Froude number Fr. The sensitivity analysis reveals that the influence of a/A is relatively strong.