含植物河道曼宁阻力系数的研究

含植物河道的水流阻力不仅仅来源于边壁,传统的曼宁公式不能够直接用来计算这种河道的糙率。本文基于水流阻力等效原则,首次提出了一系列等效水力参数的概念,建立了等效综合曼宁糙率系数和等效植物附加曼宁系数的计算公式,并给出了能否使用水深代替水力半径的判别参数。使用刚性圆柱棒进行水槽试验,对植物在非淹没和淹没条件下的曼宁系数进行了计算和比较。试验结果验证了理论分析提出的关于判别参数的结论,并且表明使用水深计算的糙率在植物非淹没条件下可以用来表示植物引起的附加阻力。本文提出的等效综合曼宁糙率系数计算公式包含了植物的物理特性,因此具有普遍的应用价值,可以用来进行实际工程中糙率的计算。

Manning's roughness coefficient of vegetated channels

The conventional Manning's formula is not applicable to the flow in vegetated channel,since the flow resistance is composed of wall friction and vegetation resistance.In this paper,a series of equivalent hydraulic parameters based on flow resistance equivalence principle are suggested.The formulas of equivalent comprehensive Manning's roughness and the additional vegetation roughness coefficient are proposed.Besides,the condition of adopting the water depth as the hydraulic radius for hydraulic calculation is discussed.Laboratory experiments are also carried out with stiff cylinders used as vegetations to study the law of flow resistance both for emersed and submerged situations.The experimental result proves the theoretical analysis and shows that the Manning's coefficient calculated by using water depth as hydraulic radius can be used to express the additional resistance coefficient due to vegetation for emersed cases.The formula of equivalent comprehensive roughness coefficient can be applied to engineering practice.