Wake Dynamics and Vortex Interaction Around Tripile Foundations for Offshore Wind Turbines

Abstract The complex interaction of wake dynamics around tripile foundations for offshore wind turbines is investigated using large eddy simulations. The foundation consists of two cylinders at the front and one behind and is arranged in two different triangular configurations with spacing ratios of s/D = 3 and s/D = 5 (where s and D represent the spacing and cylinder diameter, respectively). A key objective is to examine the influence of the tripile configuration and variation of the spacing ratios on wake interference, vortex dynamics, and momentum transfer. The mean flow field depicts the submerged foundations obstruct free flow, which creates unsteadiness in velocity and pressure fields that lead to vortex generation and wake interactions between adjacent structures. The wake topology downstream of the submerged foundation is influenced by the interaction of the separated and reattaching flow near the foundation surfaces. The three-dimensional flow with large-scale and small-scale structures is investigated. Key flow features include Kelvin-Helmholtz instabilities, horseshoe vortices, and the transition between quadrupole and multipole wake regimes with spacing variation. The study reveals s/D = 3 led to strong wake interactions and unified vortex dynamics, characterized by vortex loops and synchronized shedding. In contrast, s/D = 5 results in reduced interference and more independent wake structures with distinct frequencies. The outcome of this study seeks to advance the design of tripile foundations, improving operational safety, reducing wake effects, and minimizing localized scour in marine environments.