Author(s): Chengguang Li; Wenxin Huai; Yuhong Zeng
Keywords: RNG k-ε turbulent model; Vegetation; Bend curvature; Velocity; Shear stress
Abstract: A RNG k-ε turbulent model combined with an experimental measurement with Micro ADV were presented herein to investigate flow in a 180°curved open channel (a 4m straight inflow section, a 180°curved section, and a 4m straight outflow section) featuring vegetation on its outer bank. A comparison between the numerical result and experimental measurement shows that the RNG k-ε turbulent model can well predict flow in the curved open channel featuring vegetation. Under the combined effect of vegetation and bend curvature, the velocities in the vegetation area are much smaller than those in the non-vegetation area. In the outer bank vegetation area, the vertical profile of velocity is much more uniform over the flow depth due to the reason that vegetation confines the bed wall roughness in a small area close to the bed, and no clear circulation is found in this area. In the non-vegetation area, the maximal velocity gradually shifts to the flume bed as heading downstream and a clear clockwise circulation is developed in curved reach. It can also be seen that there is a large mass and momentum exchange between the vegetation and non-vegetation area in the whole process. In addition, the small value of the wall shear stresses in the vegetation area shows that vegetation can protect the river bank from scour and erosion effectively. However, at the same time, the sediment is easily to be deposited in the outer vegetation area.