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Experimental Assessment of the Flow Resistance of Coastal Wooden Fences
Water ( IF 3.4 ) Pub Date : 2020-07-04 , DOI: 10.3390/w12071910
Hoang Dao , Bas Hofland , Marcel Stive , Tri Mai

Wooden fences are applied as a nature-based solution to support mangrove restoration along mangrove coasts in general and the Mekong Delta coast in particular. The simple structure uses vertical bamboo poles as a frame to store horizontal bamboo and tree branches (brushwood). Fence resistance is quantitatively determined by the drag coefficient exerted by the fence material on the flow; however, the behaviour of drag is predictable only when the arrangement of the cylinders is homogeneous. Therefore, for more arbitrary arrangements, the Darcy–Forchheimer equations need to be considered. In this study, the law of fluid flow was applied by forcing a constant flow of water through the fence material and measuring the loss of hydraulic pressure over a fence thickness. Fences, mainly using bamboo sticks, were installed with model-scale and full-scale diameters applying two main arrangements, inhomogeneous and staggered. Our empirical findings led to several conclusions. The bulk drag coefficient ( C D ¯ ) is influenced by the flow regime represented by Reynolds number. The drag coefficient decreases with the increase of the porosity, which strongly depends on fence arrangements. Finally, the Forchheimer coefficients can be linked to the drag coefficient through a related porosity parameter at high turbulent conditions. The staggered arrangement is well-predicted by the Ergun-relations for the Darcy–Forchheimer coefficients when an inhomogeneous arrangement with equal porosity and diameter leads to a large drag and flow resistance.

中文翻译:

沿海木栅栏流动阻力的实验评估

木栅栏被用作一种基于自然的解决方案,以支持红树林沿岸,尤其是湄公河三角洲沿岸的红树林恢复。简单的结构以垂直的竹竿为框架,存放水平的竹子和树枝(灌木)。围栏阻力由围栏材料对水流施加的阻力系数定量确定;然而,只有当气缸的排列均匀时,阻力的行为才是可预测的。因此,对于更任意的排列,需要考虑 Darcy-Forchheimer 方程。在这项研究中,流体流动定律通过迫使恒定的水流通过围栏材料并测量围栏厚度范围内的液压损失来应用。围栏,主要用竹签,以模型尺寸和全尺寸直径安装,应用两种主要排列方式,不均匀和交错。我们的实证结果得出了几个结论。体积阻力系数 (CD¯) 受雷诺数表示的流态的影响。阻力系数随着孔隙率的增加而降低,这在很大程度上取决于围栏的布置。最后,在高湍流条件下,可以通过相关的孔隙度参数将 Forchheimer 系数与阻力系数联系起来。当具有相同孔隙率和直径的不均匀排列导致大阻力和流动阻力时,交错排列可以通过 Darcy-Forchheimer 系数的 Ergun 关系很好地预测。体积阻力系数 (CD¯) 受雷诺数表示的流态的影响。阻力系数随着孔隙率的增加而降低,这在很大程度上取决于围栏的布置。最后,在高湍流条件下,可以通过相关的孔隙度参数将 Forchheimer 系数与阻力系数联系起来。当具有相同孔隙率和直径的不均匀排列导致大阻力和流动阻力时,交错排列可以通过 Darcy-Forchheimer 系数的 Ergun 关系很好地预测。体积阻力系数 (CD¯) 受雷诺数表示的流态的影响。阻力系数随着孔隙率的增加而降低,这在很大程度上取决于围栏的布置。最后,在高湍流条件下,可以通过相关的孔隙度参数将 Forchheimer 系数与阻力系数联系起来。当具有相同孔隙率和直径的不均匀排列导致大阻力和流动阻力时,交错排列可以通过 Darcy-Forchheimer 系数的 Ergun 关系很好地预测。Forchheimer 系数可以通过高湍流条件下的相关孔隙度参数与阻力系数相关联。当具有相同孔隙率和直径的不均匀排列导致大阻力和流动阻力时,交错排列可以通过 Darcy-Forchheimer 系数的 Ergun 关系很好地预测。Forchheimer 系数可以通过高湍流条件下的相关孔隙度参数与阻力系数相关联。当具有相同孔隙率和直径的不均匀排列导致大阻力和流动阻力时,交错排列可以通过 Darcy-Forchheimer 系数的 Ergun 关系很好地预测。
更新日期:2020-07-04
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