Experimental analysis of flow and turbulence in the wake of neighboring emergent vegetation patches with different densities

Abstract

Patches of vegetation in natural water bodies grow close to each other and may affect each other’s wake pattern with significant implications on nutrient uptake and local sediment transport. This experimental study analyzed the wakes of two neighboring circular patches of emergent artificial vegetation with different densities, with the tested solid volume fractions being equal to 0.059, 0.114, and 0.188. The neighboring patches were positioned in two different configurations, namely side-by-side ( $$L/D=0$$ and $$T/D=1.5$$ ) and staggered ( $$L/D=3.5$$ and $$T/D=1.5$$ ) configurations, with D, L, and T denoting the patch diameter, the patches center-to-center longitudinal distance, and the patches center-to-center transverse distance, respectively. Results show that neighboring patches with different densities generated two distinctly different wakes at the near downstream while after 7–10D these two wakes started merging into one. The flow immediately downstream of a patch was not significantly affected by the presence of a neighboring patch and remained similar to that of an isolated patch, besides the wake of the upstream patch in staggered configuration, which was significantly affected by the downstream patch. The solid volume fraction of the neighboring patch determined the flow velocity and turbulence intensity in between the patches, which were much different compared to measurements at the side of an isolated patch.