Experimental Assessment of the Flow Resistance of Coastal Wooden Fences

Water

卷:12

MarcelJ. F. Stive¹  HoangTung Dao¹  Bas Hofland¹  Tri Mai² 

[1] Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands;

[2] Faculty of Coastal and Offshore Engineering, National University of Civil Engineering, 55 Giai Phong Street, Hai Ba Trung District, Hanoi 100000, Vietnam;

关键词: nature-based solutions;    coastal engineering;    hydraulic gradient;    porous structures;    physical experiments;    Mekong Delta;   

DOI  :  10.3390/w12071910

来源: DOAJ

【 摘 要 】

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 ( $\overline{C_D}$ ) 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.

【 授权许可】

Unknown