曼宁公式在粗糙壁面明渠流的适用性研究

Study on the applicability of Manning formula to flow in rough wall open channel

为减少因糙率系数的取值不当引起的水力特性计算误差,将明渠流与圆管流进行比较,利用数值软件对粗糙壁面进行模拟,采用三维双精度的k-ε紊流模型建立一个具有沙质床面的明渠流模型,并运用相似理论对其进行缩尺实验,统计床面阻力及沙粒阻力并绘制受力响应曲线。采用加权几何平均的数据处理方式对数模计算结果分区进行分析整合,得出粗糙壁面在阻力二次方段、过渡段和阻力一次方段阶跃曲线本构关系。结果表明,曼宁公式只在阻力二次方段是严谨的,而基于受力严格推导出来的公式在阻力一次方段和过渡段上更适用。

Roughness coefficient is significance to the calculation of open channel.In order to reduce the calculation error of hydraulic characteristics caused by improper value of roughness coefficient,the open channel flow was compared with the round pipe flow,the rough wall surface was simulated by numerical software,a channel flow model with sandy bed surface was established by using the Three-Dimensional double precision k-turbulence model,and the scale experiment was carried out by using the similarity theory.The bed surface resistance and sand particle resistance were calculated,and the force response curve was drawn.The weighted geometric average data processing method was used to analyze and integrate the numerical simulation results,and the constitutive relationships of the step curves of the rough wall surface in the quadratic resistance section,the transition section and the first power resistance section were obtained.The results show that manning's formula is strict only in the quadratic resistance section,while the formula derived strictly based on the force is more applicable in the first power resistance section and the transition section.