弯道近岸流速沿程分布规律与计算方法

Longitudinal Distribution Law and Calculating Method of Near-bank Velocity in Successive Bends

确定弯道近岸流速对于预测弯道凹岸侵蚀速率与横向迁移速率具有重要意义,但野外测量与理论计算近岸流速困难较多。为研究近岸流速的沿程分布规律,以及近岸流速与断面平均流速值之间的定量关系,采用MIKE 3建立水流数学模型,分析各种工况下连续弯道的中间河段内18个断面的断面平均流速与近岸流速的关系并建立计算方法。结果表明,弯道入口段,近岸流速沿程略减小,之后沿程近似呈线性增加。近岸流速随断面平均流速的增加而增加,二者之间高度正相关,可采用ub=a珔u+b表示,a和b随弯道中心角和来流量变化而变化。研究成果有助于了解河道演化规律。

The near-bank water velocity is of great importance to predict erosion rate of outer bank and transverse mi- gration rate in meandering river. However, it is difficult for near-bank velocity to measure in field survey and calculate in theory. In order to study the longitudinal distribution of near-bank water velocity and explore the quantitative relationship between near-bank water velocity and cross-section average velocity, a numerical model was developed through Mike 3. Numerical data of near-bank water velocity and cross-section average velocity were analyzed at the position of 18 cross- sections in the middle reach under conditions of different discharges. The calculating method of near-bank water velocity was obtained using correlation analysis. Results show that near-bank water velocity decreases slightly at the bend entrance firstly, and then it linearly increases until at the exit of bend. Significant linear relationship is found between near-bank water velocity and cross-section average velocity. Near-bank water velocity linearly increases with cross-section average velocity with high positive correlation. The equation Ub =au＋b can be expressed the relationship, a and b vary with the central angle of bend and discharge. The research results are conducive to understanding the change laws of river channel.