Fluid-Structure Interaction Phenomena in Offshore Wind Turbines

When a flexible or flexibly-mounted structure is in contact with flow, it could deform or oscillate due to the fluid forces. The deformation or oscillation of the structure results in changes in the fluid forces, leading to changes in the structure’s response. This is called a fluid-structure interaction problem. In a floating wind turbine, many cases of fluid-structure interaction are observed. Large wind turbine blades, which are common for the offshore wind turbines, are susceptible to various flow-induced dynamical instabilities. This means that if the blades are too large, or too flexible, they can undergo large-amplitude oscillations in a plane perpendicular to the plane of rotation. The result is that the blade will break immediately, or will hit the tower. The blades are attached to a tower, which oscillates due to the interaction of the platform with the ocean waves. The entire floating wind turbine is supported by mooring lines. The platform and the mooring lines can undergo vortex-induced vibration (VIV). The amplitude of VIV is in the order of one diameter and its frequency is rather low (usually ranging from around 1 Hz to around 10 Hz). Although its amplitude and frequency are not very large, VIV is a major concern, as it can lead to fatigue and failure of the mooring lines. A failed mooring system results in a floating wind turbine moving freely in the ocean – a situation that should definitely be avoided. In this talk I will show some recent results on flow-induced instabilities of wind turbine blades, and I will discuss vortex-induced vibration of a spar buoy, modelled after one of the existing large-scale floating wind turbines.

Thursday, November 6, 2014 - 3:30pm
Integrated Sciences Building Room 221