Large eddy simulation of the flow field characteristics around a jacket foundation under unidirectional flow actions

Jacket foundation is primarily used to support the tower and fan blades of offshore wind turbines in water depths exceeding 30 m and is designed in a modular pattern and assembled on-site. However, to date, limited research has been conducted on scour and flow field characteristics around jacket foundations under complex marine conitions. This paper employs the Large Eddy Simulation to simulate flow field and sediment transport around the jacket foundation. Results indicate that, compared to flat bed condition, the maximum streamwise and vertical velocities around the jacket decrease by 17% and 13% under the scour equilibrium condition. During the initial scour stage ($t$ = 0.25 h), turbulence intensity ($TI$) and turbulent kinetic energy ($TKE$) decrease by 9% and 17%, respectively, compared to the flat bed condition. As scour progresses, both $TI$ and $TKE$ gradually increase, approaching values under the flat bed condition. Additionally, the increase in flow intensity exacerbates the scour, accompanied by increased energy dissipation within the scour pit. The flow field characteristics around the back pile of the jacket are influenced by the energy dissipation as well as by sand dunes formed between piles. The flow field characteristics around the jacket foundation are minimally affected by water depth.