The Role of Angled Vegetation in Modifying Hydrodynamic Properties Around Dike

Abstract

The position of vegetation patches has a considerable impact on river flow structure and geomorphology. The influence of vegetation patch orientation in the form of an angled position along the side by the dike wall, notably on the subsequent flow characteristics and turbulence, was computationally investigated in the present research work. Reynolds-averaged Navier–Stokes (RANS) equations were adopted for turbulence modelling, and tetrahedral meshing was adopted for measuring the accurate flow phenomenon around the vegetation patch by using 3D commercial software ANSYS FLUENT. Six different angles of vegetation patch were tested (θ = 0°, 30°, 60°, 90°, 120° and 150°) along the dike wall. Initially, the results of numerical model were validated using previously published data. This paper presents the results in the form of different profiles and contour plots depicting the mean streamwise velocity, turbulent kinetic energy (TKE), eddy viscosity and Reynolds stresses at specific critical locations and sections simulated by the model. The results showed that the current numerical model can successfully replicate the flow characteristics. The mean streamwise velocity profiles and contour plots revealed that the largest velocity was generated by vegetation patches orientated at 60°, 90° and 120° along the dike because of maximum flow resistance, which should be avoided. The velocities on the downstream side of the vegetation patch were significantly reduced across all orientations. The Reynolds stress profiles (u‘u’, v‘v’ and w‘w’) indicated that the stresses were lower near the bed and tended to become constant along the flow depth, whereas the TKE was larger inside the vegetation patches during all orientations because of turbulent flow. All angles of the vegetation patch changed the flow patterns, resulting in the formation of recirculation zones and secondary currents around the patch, which was represented in eddy viscosity contours. This study's results show that the flow dynamics in open channels are significantly affected by the orientation of the plant patch.