Analytical Model of the Velocity Profiles in Open Channel Flows with the Existence of Double Layered Vegetation

The vertical velocity in open channel flow with the existence of double layers vegetation could be divided to two different layers; by assuming the tall vegetation to be in emergent condition. The layers have been defined as: layer 1 where the flow is below the height of short vegetation and layer 2 is from the short vegetation height to free surface of the flow. In this study, a new analytical model has been proposed to predict the vertical distribution of stream wise velocity in open channel with two different height of vegetation. The current analytical study has been done based on momentum equation of flow where turbulent eddy viscosity has been assumed to have a linear relationship with the local velocity. The new analytical model has been calibrated by experimental studies done by Liu et al. (2008) and Huai et al. (2014) and in order to cover more scenarios and formations some other double layers vegetation have been done by authors in Hydraulic Laboratory of Nanjing Hydraulic Research Institute and velocity data have been collected by ADV, Acoustic Doppler velocimetry made by Nortek company. Generally, 11 different experiments with different densities, formations and flow depths have been tested to calibrate the analytical model. Good agreement between the experimental data and analytical model indicated the validity of the model.

Keywords: Double layer vegetation, Emergent vegetation, Open channel flow, Submerged vegetation, Velocity profiles.