Hydrodynamic and turbulent wake characteristics in response to sacrificial piles

Sacrificial piles are a potential scour mitigation measure, but their application to offshore wind turbine foundations remains limited. Their effects on tidal currents, the vorticity balance, and turbulent wake recovery under reversing flow remain unclear. This study investigates the hydrodynamic mechanisms through which sacrificial piles modify monopile wake structures, with a focus on the underlying dynamical forcing, vorticity budget, and turbulence evolution. Results show that sacrificial piles fundamentally reshape the tidal-current structure by modifying the balance of driving forces, in which barotropic pressure gradient (xba) dominates, combined with horizontal nonlinear advection (xadh) at the surface and vertical nonlinear advection (xadv) at the bottom. Analysis of the vorticity budget reveals that sacrificial piles also amplify the dominant vorticity-budget terms, including the advection of relative vorticity (varv) and the barotropic curl (vbac) by approximately 2.5–3 times compared with the monopile-only case. In terms of turbulence characteristics, sacrificial piles increase subsurface wake intensity while exerting limited influence on wake width. The transverse configuration amplifies relative excess turbulence by a factor of 2–5, whereas the triangular configuration produces stronger near-field turbulence enhancement, with peak values reaching five to seven times. At recovery thresholds of Δ = 1 and 0.1, the triangular configuration has the longest downstream recovery distance; at Δ = 0.01, the transverse configuration has the longest. These findings advance the understanding of the hydrodynamic effects of sacrificial piles and establish a framework for future investigations that incorporate sediment transport, morphological evolution, and field-scale validation.