Effect of scour erosion on mode shapes of a 5 MW monopile-supported offshore wind turbine

This paper investigates the influence of scour erosion on mode shapes National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine (OWT) in varying soil conditions, where modes are derived from and wave-induced accelerations. A numerical model, which considers aerodynamic hydrodynamic loading with soil-structure interaction (SSI) servo-dynamics, is developed. The superstructure modelled using OpenFAST foundation SESAM, SSI incorporated Winkler (p-y) springs. stiffness subsequently integrated mudline interface density, hole depth, studied. Accelerations extracted at nine locations along tower. first two system natural frequencies estimated frequency domain decomposition (FDD) applied to acceleration time-histories for each depth condition. Modal Assurance Criterion (MAC) values calculated evaluate changes that occur due scour. It shown present consistent as increases, second shape exhibits more sensitivity under variations speed measurement noise also investigated.