Parametric study of the hydrodynamics of a mangrove root model

Mangrove trees can be found along (sub)tropical coastlines all over the world. Their roots act as obstacles for tidal currents, dissipating energy and providing coastal protection.  Over the last century, a large portion of mangrove forests has been lost due to human activity, leading to remediation efforts that include man-made mangrove-like structures. Parametrization of the hydrodynamics of complex root networks is key to mimic a bio-inspired structure for coastal protection. In this study, we carried out a series of experiments on a simplified root patch, consisting of a symmetrical array of cylindrical rods in a radial arrangement, where we explore the effect of flow velocity, root size, porosity and stiffness on the drag experienced by the root patch. The patch models were fully submerged and tested at Reynolds numbers Re ∼ 10³-10⁴.  Direct force and wake velocity measurements were performed on the patch. Dimensional analysis of the experimental results indicates that the root pitch and the effective patch diameter (obtained from the shedding frequency) are good indicators of the drag experienced by the patch. Our results will provide a baseline in the design and optimization of man-made structures used for coastal protection and potential energy harvesting.