<p>Computational Fluid Dynamics (CFD) has been established as a relevant technique to investigate the qualitative and quantitative characteristics of complex environmental flows, such as transient storage zones. In numerical studies involving mass transport of solutes and sediment (e.g., mean retention time and mass exchange rate), one fundamental variable is the turbulent Schmidt number (Sct) which defines the ratio of momentum diffusivity to mass diffusivity in turbulent flows, and thus affects the concentration of solute within the solution impacting on the estimation of mass related variables. This is particularly important for transient storage zones, such as lateral cavities and groyne fields, as they are known for their role in nutrient retention and release, and sediment entrapment. This numerical study aims to examine the influence of the turbulent Schmidt number in the mean retention time and mass exchange rate between a channel and a vegetated/non-vegetated lateral cavity.</p><p>&#160;</p><p>The cavity was <em>L</em> = 0.25m long (x-axis), <em>W</em> = 0.15m wide (y-axis) and had a depth of <em>H</em> = 0.10m (z-axis). The aspect ratio between the width and the length resulted in 0.6 which corresponded to a single circulation system (Sukhodolov et al., 2002). The flow had a bulk velocity of&#160;<em>U</em> = 0.101 m/s that corresponds to a Reynolds number of 9000. The vegetation drag was represented by an anisotropic porous media calculated with the Darcy-Forchheimer model (Yamasaki et al., 2019), the vegetation density was constant at <em>a</em> = 0.1332%. Large Eddy Simulation (LES) was applied to define the flow field in that domain, using the Wall Adapting Local Eddy-viscosity (WALE) to account subgrid effects. A passive scalar was injected inside the lateral cavity to investigate its transport and diffusion in a range of Sct from 0.1 to 2.0. The numerical results of the flow field were validated using literature experimental data considering 3 different meshes to achieve mesh independence (Xiang et al., 2019).</p><p>&#160;</p><p>The effect of Sct variation was, then, analysed in both vegetated and non-vegetated scenarios, for a total of 40 different simulations. The volumetric average scalar concentration in the cavity was fitted into a first-order decay model <em>(C</em> = <em>C<sub>0</sub>.e<sup>-t/T<sub>D</sub></sup></em>), where&#160;<em>C<sub>0</sub> = 1</em> is the initial concentration,&#160;<em>t</em>&#160; (s) is time and&#160;<em>T<sub>D</sub></em>&#160; is the mean residence time. The mass exchange rate was defined as&#160;<em>k</em> =&#160;<em>W/(T<sub>D</sub>.U)</em> . Preliminary results showed in the vegetated scenarios a limited effect of Sct on the mass exchange rate, which varied from 1% if the Sct value was doubled.</p><p><strong>References</strong></p><p>Sukhodolov, A., Uijttewaal, W. S. J. and Engelhardt, C.: On the correspondence between morphological and hydrodynamical patterns of groyne fields, Earth Surf. Process. Landforms, 27(3), 289&#8211;305, doi:10.1002/esp.319, 2002.</p><p>Xiang, K., Yang, Z., Huai, W. and Ding, R.: Large eddy simulation of turbulent flow structure in a rectangular embayment zone with different population densities of vegetation, Environ. Sci. Pollut. Res., 26(14), 14583&#8211;14597, doi:10.1007/s11356-019-04709-x, 2019.</p><p>Yamasaki, T. N., de Lima, P. H. S., Silva, D. F., Preza, C. G. de A., Janzen, J. G. and Nepf, H. M.: From patch to channel scale: The evolution of emergent vegetation in a channel, Adv. Water Resour., doi:10.1016/j.advwatres.2019.05.009, 2019.</p>
This work presents an approach to point cloud segmentation for Foreign Object Debris (FOD) detection in flight tracks and a proposal for their complete removal process. It is part of the methodology the use of two approaches, one using regions based method and the other using a hybrid method. The term FOD or foreign object is used for objects not belonging to flight lanes and taxiways of airports. The existence of FOD in flight lanes is a recurring problem in aviation in general, which must be kept under constant monitoring. The consequences of this problem range from high aircraft maintenance costs to overhead expenses such as hotel nights due to delayed flights. The approaches proposed here fall under a process of detection and removal of debris. The proposed differential is the use of pre-processing in the raw data, from the capture sensor, to improve the results of the segmentation of objects. In the removal process it is proposed the use of a robot integrated with the detection systems already present on the tracks. For validation of the methods, a comparative analysis between some of the main works in this area will be presented, as well as tests in a set of data for demonstration of the results. Resumo: Este trabalho apresenta uma abordagem para segmentação de nuvem de pontos para detecção de FOD (Foreign Objects Debris) em pistas de voo e uma proposta para o processo completo de remoção. Faz parte da metodologia de segmentação a utilização de duas abordagens, uma com método baseado em regiões e a outra com um método híbrido. O termo FOD ou objeto estranhoé utilizado para objetos intrusosàs pistas de voo e taxiamento dos aeroportos. A existência de FOD em pistas de vooé um problema recorrente na aviação de forma geral e que precisa estar sempre em monitoramento. As consequências deste problema vão desde altos valores gastos com manutenção dos aviões até com despesas indiretas como diárias em hotéis devido ao atraso de voos. As abordagens propostas aqui se enquadram em um processo de detecção e remoção dos FOD's. O diferencial propostoé a utilização de pré-processamentos nos dados brutos, oriundos do sensor de captura, para melhoria nos resultados da segmentação dos objetos. No processo de remoçãoé proposta a utilização de um robô integrado aos sistemas de detecção já presentes nas pistas e que faz uso do processo de detecção citado. Para validação dos métodos, uma análise comparativa entre alguns dos principais trabalhos nestaárea serão apresentados, assim como testes em um conjunto de dados para demonstração dos resultados.
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