Insight into the unsteady aerodynamics of floating wind turbines with Tension Leg Platforms (TLP) using a Blade Element Momentum (BEM) based model

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Floating wind turbines are subject to more complex dynamic behaviour than those mounted on fixed foundations. Such behaviour is dictated by the interaction of the hydrodynamic forces on the floater, the aerodynamic loads on the turbine as well as the gravitational and inertia loads. Numerical simulation tools provide a valuable aid for obtaining further insight about the aerodynamics of floating wind turbines. A full-scale 5MW floating wind turbine model has been analyzed using a commercial numerical tool The unsteady aerodynamic effects were simulated using a BEM- based model modified to account for dynamic inflow effects. Simulations under normal operation were conducted for a range of different wind speeds and tip speed ratios of the turbine rotor. One-directional water wave conditions were used in all simulations. Various parameters predicted by the simulation as a function of time where analyzed. These included the power output, power coefficient, and rotor axial thrust together with local blade parameters (including the angle of attack, velocities, lift and drag coefficients). Relationships were highlighted between the varied loading conditions. Furthermore, the results for the oscillating wind turbine were compared with those for the same turbine operating in a steady environment (i.e. with a rigidly fixed foundation).