Influence of Model Simplifications Excitation Force in Surge for a Floating Foundation for Offshore Wind Turbines

Abstract

Abstract:As offshore wind turbines move towards deeper and more distant sites, the concept of floating foundations is a potential technically and economically attractive alternative to the traditional fixed foundations. Unlike the well-studied monopile, the geometry of a floating foundation is complex and, thereby, increases the difficulty in wave force determination due to limitations of the commonly used simplified methods. This paper deals with a physical model test of the hydrodynamic excitation force in surge on a fixed three-columned structure intended as a floating foundation for offshore wind turbines. The experiments were conducted in a wave basin at Aalborg University. The test results are compared with a Boundary Element Method code based on linear diffraction theory for different wave force regimes defined by the column diameter, wave heights and lengths. Furthermore, the study investigates the influence of incident wave direction and stabilizing heave-plates. The structure can be divided into primary, secondary and tertiary parts, defined by the columns, heave-plates and braces to determine the excitation force in surge. The test results are in good agreement with the numerical computation for the primary parts only, which leads to simplified determination of peak frequencies and corresponding dominant force regime.

Investigation of Hydrodynamic Forces for Floating Offshore Wind Turbines on Spar Buoys and Tension Leg Platforms with the Mooring Systems in Waves

“…At present, the well-known modular system is ETAP Wind Turbine Modeling (WTM) software [23], which is used to design and monitor wind farms in a flexible graphic interface optimized for wind power simulation and analysis. Andersen, Hindhede [24] indicated that the Swim-Motion-Lines (SML) software suite is applicable to the maritime and offshore industries for calculating motion responses of floating platforms in winds, waves, or currents. SML is composed of three modules: the SWIM module is used to calculate hydrodynamic forces in the frequency domain; the MOTION module is adopted to simulate a slow-drift response in the time domain; and the LINES module is employed to estimate the influence of the mooring system on the floating platform.…”