It is widely recognized that seabed scour around offshore wind turbine foundation (OWTF) considerably influences performances of wind turbine such as bearing capability and dynamic responses. Thus a proper model is required to estimate seabed scour around OWTF. Some investigations have been conducted to predict scour around monopile, jacket and bucket foundation. However, scour around more-than-three-inclined- pile group OWTF is rarely investigated. Herein, Fluid is described with mass conservation law, momentum theorem, RNG turbulence closure model and VOF for free surface. Shields parameter is chosen as scour criterion. The transport of suspended sediment is governed by conservation law and momentum theorem. OWTF is simplified as wall boundary. The constructed model is used to estimate current-induced scour around eight-inclined-pile group foundation, scour topography is predicted and scour evolution with time is also estimated. Though the case study only takes current into account, model in this paper could be easily extended for wave-induced and wave-plus-current-induced scour around OWTF by changing the inlet and outlet boundaries.
Wind is one of the most popular new energies due to its environmental friendliness and large reserve in the world. Offshore wind is steadier with larger speed than land wind, so it is an important part of exploiting wind energy. However, some difficulties are confronted (Zhou and Lin, 2013) because of the complicated ocean environment such as wind, wave, current and soft seabed. One of the challenges is seabed scour around offshore wind turbine foundation (OWTF). Local scour around OWTF directly reduces the embedded length of pile(s). Consequently, the capacity, deformation, and dynamic responses of OWTF are changed. It was discovered that the scour depth has such a significant negative impact on dynamic responses of offshore wind turbine (OWT) that engineers must pay enough attention to it (Yan, Gu, Lu and Lin, 2011). According to Xue, Wang, and Yang (2012), scour may increase deformation and decrease bearing capacity of OWTF. With a small scale physical model test and a full scale FEM simulation. Prendergast, Gavin and Doherty (2015) found that wind turbines with loose sand seabed would show the largest relative reductions in natural frequency caused by scour. Additionally, some researchers put efforts on the scour protection for OWTF (Chen, Yang and Hwung, 2014; Matutano, Negro, López-Gutiérrez and Esteban, 2013; Whitehouse, Harris, Sutherland and Rees, 2011). Therefore, it is a wide recognition that seabed scour around OWTF considerably influences performances of wind turbine.
