Two-zone analysis of velocity profiles in a compound channel with partial artificial vegetation cover

In this study, experimental and theoretical methods are used to investigate the longitudinal velocity profiles in a channel partially covered with novel artificial vegetation. Due to the discontinuity of the drag force of the artificial vegetation in the lateral direction, the experimental data of longitudinal velocity in the partially covered channel shows a two-zone flow structure. The measured profile of shear stress reaches its peak at the interface between the vegetation and non-vegetation zones and it has a slowly changing boundary layer in the non-vegetation zone. The velocity difference causes the formation of a dominant vortex across the zone interface that contributes to the lateral transport of momentum and mass. Hence, a vortex-based model based on a momentum balance is utilized to predict the lateral distribution of the longitudinal velocity. Meanwhile, the expression of the momentum penetration distance induced by the coherent vortex into the vegetation zone is developed. The predicted and measured velocities are consistent within a relative error of 4%–6%. The two-zone analysis of velocity profiles paves the way for the turbulent structure to be examined future in partially artificial vegetated channels.