Full-Scale Numerical Simulation of the Local Scour Under Combined Current and Wave Conditions Based on Field Data

The monopile is the most common foundation to support offshore wind turbines. In the marine environment, local scour due to combined currents and waves is a significant issue that must be considered in the design of wind turbine foundations. In this paper, a full-scale numerical model was developed and validated based on field data from Rudong, China. The scour development around monopiles was investigated, and the effects of waves and the Reynolds number Re were analyzed. Several formulas for predicting the scour depth in the literature have been evaluated. It is found that waves can accelerate scour development even if the KC number is small (0.78< KC <1.57). The formula obtained from small-scale model tests may be unsafe or wasteful when it is applied in practical design due to the scale effect. A new equation for predicting the scour depth based on the average pile Reynolds number ( Re a ) is proposed and validated with field data. The equilibrium scour depth predicted using the proposed equation is evaluated and compared with those from nine equations in the literature. It is demonstrated that the values predicted from the proposed equation and from the S/M (Sheppard/Melville) equation are closer to the field data.