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.

A escassez de água é um problema cada vez mais severo em todo o mundo devido a fatores como o consumo excessivo de água bruta, as mudanas climáticas, a poluição da água e o consumo insustentável dos recursos hídricos. Sob essas condições, formas tradicionais ou alternativas de recursos hídricos, tais como a água pluvial, estão sendo consideradas como opções atrativas para reduzir o consumo de água potável. Neste contexto, este artigo descreve o cenário de disponibilidade de água na região Amazõnica, Noroeste do Brasil, e avalia o potencial da economia de água potável para o setor residencial em 40 cidades da região. Os resultados indicam que o potencial da economia de água potável varia entre 21 e 100%, dependendo da demanda de água potável verificada nas 40 cidades, com potencial médio de 76%. A prisncipal conclusão desta pesquisa é que, se houvesse um programa do governo para promover a economia de água potável por meio da utilização da água pluvial, haveria significativa economia de água potável e, consequentemente, a preservação dos recursos hídricos na Amazõnia.

The influence of inlet momentum and inlet orientation on hydraulic performance of cylindrical water process tanks were investigated using a factorial design strategy. The hydraulic performance of the tanks was assessed with a computational fluid dynamics (CFD) model, which calculated the flow fields and the residence time distribution (RTD). RTDs were used to quantify the tanks hydraulic performance using hydraulic indexes that represent short-circuiting, mixing, and moment. These indexes were later associated with the effluent fraction of disinfectant (inlet and outlet disinfectant ratio). For small depth-to-diameter ratios, the inlet orientation and the inlet momentum were the most important factors regarding the hydraulic indexes and the effluent fraction of disinfectant, respectively. A poor correlation was obtained between the hydraulic indexes and the effluent fraction of disinfectant, indicating that they are not good predictors for water quality. For large depth-to-diameter ratios, the inlet orientation had the most significant effect on both the hydraulic indexes and effluent fraction of disinfectant. The short-circuiting and mixing indexes presented a good correlation with water quality for this case.

Turbulence generated by a pair of oscillating grids in a water tank is investigated using the digital particle image velocimetry technique. Vertical and horizontal components of fluctuating velocities are measured. Experimental profiles of the turbulent kinetic energy k, and the energy dissipation rate, xi, obtained from the fluctuating velocities, are presented and compared with theoretical predictions. Other properties of interest, such as the length scale and the turbulent viscosity, obtained in the present study, are also reported. The turbulence generated with the pair of grids may be classified as "nearly isotropic" and theoretically the flow may be analyzed using the k-epsilon model. The experimental data agree well with the theoretical predictions. Also data of different sources found in literature, for pairs of vibrating grids, are compared with the present experimental results and theoretical predictions, showing good agreement. The studies conducted at the Laboratory of Environmental Hydraulics from the Department of Hydraulics and Sanitary Engineering, EESC/USP, permits to affirm that "double oscillating grids" turbulence can be viewed as nearly isotropic