Influence of Neighboring Vegetation Patches on Flow Structure Characteristics with Different Densities
Vegetation patches constitute the foundational elements of river dynamic systems,often forming communities within channels.This study examines how the interaction between neighboring vegetation patches influences flow structure.A pair of adjacent vegetation patches,con-structed from staggered rigid cylinders with varying densities,is used in the experiments.The findings indicate significant differences in flow structure when water traverses these adjacent patches compared to an isolated patch.Hence,a flow structure partition for adjacent patches is pro-posed,including an upstream adjustment region,a vegetation interior region,a shear layers region,and a wake merger region.The upstream ad-justment length indicates the distance upstream from the obstruction where velocity starts to deviate from its far upstream value.This reduction in velocity is pronounced in denser patches,although the upstream adjustment length remains unaffected by vegetation density.The velocity at the centerline of each patch significantly decreases,whereas the velocity between the patches increases rapidly,a characteristic of the vegetation in-terior region.The reduction in individual patch velocity is again observed in denser patches.In the downstream area,the shear layers region ex-tends from the trailing edge of the patches to the point of minimal velocity behind each isolated patch.With increasing vegetation density,the smallest velocity approaches zero,while the length of the shear layers region,denoted as L1,initially decreases before stabilizing.The highest ve-locity on the centerline between the patches occurs near the trailing edge,with the lowest velocity observed at a distance(x/D=Lm)from the trail-ing edge.As vegetation density increases,the maximum velocity on the centerline between the patches rises,but the minimum velocity and Lm de-crease.The difference(Lm-L1)defines the length of the wake merger region;here,the centerline velocity of each patch increases and aligns with the velocity on the centerline between the patches,causing the wakes directly behind each patch to merge into a single,larger entity.In addition,the formulas for the exit velocity,steady wake velocity,and minimum centerline velocity of the two patches are presented.
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NSTL
万方数据
维普
