The mechanism of the flow resistance in open channels and pipelines is of vital importance for various critical issues related to the water flow. The Nikurade’s method of calculating the friction factor is not applicable in some cases. It is necessary to consider the influence of the vortex volume surrounding the vegetation and to study the hydrodynamic characteristics of the vegetated channels. This paper analyzes the variation of the vortices created by the surface roughness of different types and different sizes and proposes new definitions of the hydraulic radius and the equivalent roughness height. With consideration of the skin friction and the form drag, on the basis of the force balance equation, a novel calculation method is used for the friction factor, and this method is verified by experimental data. The hydrodynamic mechanism of the flow resistance revealed in this study may serve as a theoretical basis for hydraulic engineers to calculate the friction factor.

明渠和管道中的流动阻力机制对于与水流相关的各种关键问题至关重要。Nikurade 计算摩擦系数的方法在某些情况下不适用。需要考虑植被周围涡量的影响，研究植被通道的水动力特性。本文分析了不同类型、不同尺寸的表面粗糙度所产生的涡流的变化，并提出了水力半径和等效粗糙度高度的新定义。考虑蒙皮摩擦和形式阻力，在力平衡方程的基础上，采用了一种新的摩擦系数计算方法，并通过实验数据验证了该方法。