Numerical Simulations of Mangrove-Inspired Sacrificial Pile Group for Scour Mitigation

Mangroves stabilize coastlines, partially through a porous ‘forest’ of trunks and aerial roots, which reportedly dissipate wave energy and reduce flow velocity. It is hypothesized that not only the vertical but also the horizontal components of the ‘forest’ contribute to the altering of flow field which mitigates scour. To test the hypothesis, the effect of a modified sacrificial pile group consisting of vertical mini-piles and (semi-) horizontal crossbars on the flow field around a downstream monopile is studied using computational fluid dynamics (CFD). The simulation results confirmed that the group of mini-piles significantly reduces both the horizontal and vertical velocity in front of the monopile as well as the flow-induced shear force at the bed. The presence of the crossbars reduces the horizontal velocities further, but more importantly, it helps significantly reduce or even reverse the downward flow at the front near the base of monopile. Such changes to the flow field are expected to reduce the strength of the horseshoe vortex and reduce local scour.