明渠侧向取水受取水口门形态的约束,水流流态紊乱,对支渠引水影响很大。对此采用Mike21数值模拟手段模拟三种边坡系数分别为0、1、2的断面在流量1-10L/s下的水流运动,分析分流口门处的流态,研究各参数对分流比的影响。研究结果表明：相同边坡系数,随着上游来流流量的增加,回流区范围增大,有效宽度减小,收缩系数减小,分流比减小；相同流量,随着边坡系数的增大,支流内回流区范围变小,有效宽度增加,收缩系数增大,分流比增大；随着弗劳德数的增加,分流比逐渐减小,且边坡系数越大,变化越明显。最后获得了分流比与弗劳德数与收缩系数之间的关系式,相关度较好,并得到了验证。

Lateral intakes in open channel are often used for diverting water from river,which has a great impact on the flow regime because of the constraint near the intake mouth． Those factors influence the branch ditch heavily． With the complicated regime in diversion of tributary,the simulation model was established to analyze hydraulic characteristics of bifurcation area based on MIKE21,a model for plane－2D flow． The flow under three slope coefficients 0,1 and 2 respectively are simulated with discharge varying from 1 L/s to 10 L/s． The flow pattern at the entrance of the diversion and the influence of the parameters on the diversion ratio are analyzed and studied． The results show that,under the same slope coefficient,the range of recirculation zone increases,the effective width of branch decreases,the contraction coefficient decreases and the diversion ratio decreases with inlet discharge increasing． Under a fixed discharge,the range of recirculation zone decreases,the effective width of branch increases and the contraction coefficient and the diversion ratio increases with slope coefficients increasing． With Froude number increasing,the diversion ratio decreases gradually with larger the slope coefficient． The relationship among the diversion ratio and the Froude number and the contraction coefficient is obtained,the correlation coefficient is good and has been verified．