Numerical Simulation Study On The Finite Emergent Rigid Vegetated Flow

Vegetation is an important part of the ecological environment.The study of the vegetated flow will contribute to the understanding of the river evolution,the interaction of water and sediment as well the ecological management.Based on the previous researches,a group of staggered cylinders were used to represent the rigid finite vegetated patch.The 3-D numerical simulations were performed using an in-house hydrodynamic modelling package called Hydro Flow?.The accuracy of the numerical model was verified against published experimental data.The characteristics of the vegetated flow were investigated systematically by varying the solid volume fraction,inflow velocity and water depth.The patch-scale shear layers can form on the edges of the vegetated patch and develop along the flow direction.The penetration scale ?I distributes unevenly inside the patch where its maximum scale is less than 1/5 of the patch diameter.Behind the patch,the width of the patch-scale shear layer grew linearly along the flow direction and its growth trend does not change varying the velocity and the water depth.In the flow field,the violent turbulence regions mainly locate on the wake region affected by the shear layer,the near-trail region behind the patch and the wake oscillation region.Inside sparse vegetated patch,interactions between neighboring individuals are much weaker than that inside the dense.In the wake region,however,the turbulence behind the dense patch was stronger than that behind the sparse one.The bed shear stress is one of the key factor affecting the scour of the sediment on the bed.Compared with the sparse vegetated patch,the dense one can apparently suppress it in the upstream and the wake region,while the bed shear stress is much stronger on the region near the transverse sides of the patch.