A semi-analytical model for the velocity profile in an open channel with suspended rigid vegetation

Abstract

Aquatic suspended vegetation increases a significant flow resistance at the water surface, resulting in a hyperbolic-type velocity distribution in the gap between the vegetation and bed, similar to the flow in a channel covered with ice sheets. To depict the hydraulic mechanism from the bed to the free surface in both the vegetated and non-vegetated portions of the suspended vegetation flow, the four interconnected zones of flow—the interior vegetation layer, vegetation shear layer, near vegetation layer, and bottom boundary layer—must be modeled. Based on the mixing-length concept, this study proposed a novel semi-analytical model to predict the vertical velocity distribution in the open channel flow covered with suspended rigid vegetation. The shear stress in the interior and non-vegetation region was calculated using the mixing length theory, and a few parameters were established using Plew’s extensive laboratory tests and published data. The proposed model makes good predictions with data for various vegetation conditions. These findings show that the suggested model can accurately predict the vertical velocity profiles in the case of suspended vegetation. Based on five parameters—the drag coefficient, mixing length constants, penetration depth, and the location of the highest velocity—the current results demonstrate that the zone-wise suggested model may be utilized to forecast the vertical velocity distribution in suspended vegetation.