Flow patterns around two neighboring patches of emergent vegetation and possible implications for deposition and vegetation growth

The flow around two neighboring, circular, vegetation patches of equal diameter (D) was investigated using computational fluid dynamics. Depending on the patches' transverse and longitudinal center-to-center spacing (T and L, respectively), several distinct flow patterns were observed. The patterns are compared to flow near an isolated patch. The key flow patterns were interpreted in terms of implications for deposition. Deposition maps were calculated for two different threshold velocities: 0.5U(0) and 0.7U(0), where U-0 is the free stream velocity. When the two patches were far away from each other, the interaction of their wakes was weak, and the flow and deposition pattern around each patch resembled that of a single, isolated patch. When the patches were very close, wake interaction took place, resulting in additional deposition along the centerline between the two patches, but further downstream than the deposition in line with each patch. For some intermediate patch spacings, the wake of the upstream patch was dramatically shortened, relative to an isolated patch, and the wake of the downstream patch was lengthened. The results show that flow distribution is influenced by interaction between neighboring vegetation patches and suggest that this may create feedbacks that influence the evolution of vegetated landscapes.