We investigate the fluid flow through two-dimensional ramified structures by direct simulation of the Navier-Stokes equations. We show that for trees with n generations, the flow distribution strongly depends on the Reynolds number Re. Specifically, for a tree without loops the flow becomes highly heterogeneous at high Re. For a tree with loops, on the other hand, the flow distribution tends to be more uniform at increased Re conditions. We show that these apparently contradictory behaviors have the same origin, namely, the effect of inertia on the momentum transport in the channels of the ramified geometry. In order to simulate the propagation of the flow imbalance throughout the tree without loops, we develop a simple model that incorporates the basic fluid dynamics features of the system. For large trees, the results of the model indicate that the distribution of flow at the outlet branches can be described by a self-affine landscape. Finally, we argue that the nonuniform partitioning of flow found for the structure without loops may contribute to the morphogenesis and functioning of the bronchial tree.
Most of the energy consumed worldwide comes from non-renewable sources, such as oil derivatives, making it necessary to search for renewable, clean energy sources, with emphasis on biomass from agricultural and industrial waste. Coconut shell pellets (CSPs) and cashew nut shell pellets (CNSPs) were manufactured and subsequently subjected to chemical, thermal and exhaust gas analyses of their combustion. Mean temperature results in the combustion area were 366.44 ± 84.79°C (CSPs) and 295.00 ± 89.47°C (CNSPs). The exhaust gas combustion values were 19.43 ± 0.57% (CSPs) and 18.75 ± 0.77% (CNSPs) of O2, 2348 ± 1241 ppm (CSPs) and 2901 ± 499 ppm (CNSPs) of CO, 14.92 ± 5.06 ppm (CSPs) and 39.83 ± 10.91 ppm (CNSPs) of NOx, and 441.25 ± 130.41 ppm (CSPs) and 2841.50 ± 765.26 ppm (CNSPs) of CH4. In conclusion, the combustion process of CSPs proved to be less polluting and more energy efficient when compared with CNSPs. The analyses of the exhaust gases from the combustion of these biomasses can serve as a basis for the creation of safety parameters and public policies to regulate the use of biomass for energy purposes.
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