QUANTIFICATION OF AEROELASTIC RESPONSE OF BLADETOWER INTERACTION IN MULTIMEGAWATT WIND TURBINES
Produktform: Buch
The trend in the current development of modern horizontal axis wind turbines
(HAWTs) is towards light-weight, bigger rotor diameter and longer towers. The bigger,
lighter and more flexible structure is more dynamically active and sensitive to
smaller excitations. Furthermore, with increasing tower length the tower base becomes
bigger and transportation problems appear. Nowadays, tower dimensions have almost
reached roads limits. On the other hand, the influence of external factors such as wind
shear and rotor-tower interaction become more important. To ensure that the dynamic
behavior of the wind turbine structure will not influence the stability of the system and
to further optimize the structure dimensions, a fully detailed analysis of the entire wind
turbine structure is essential. Hence, the aim of this work is to investigate the bidirectional
blade-tower interaction of a multi-megawatt upwind HAWT.
A high-fidelity aeroelastic model based on fluid-structure interaction is presented. The
blade aerodynamics was predicted from solving the unsteady incompressible Navier-
Stokes equations by means of computational fluid dynamics (CFD), while structure
deformation was calculated using finite element (FE). The dynamic response of the
wind turbine structure is accomplished in a strongly coupled manner. Both elastic
blade and tower are considered, where the blades are modeled as an equivalent cantilever
beam while the tower is discretized into finite elements.
The numerical model provides insight into wind turbine aerodynamic performance and
structure behavior. The study showed that passage of the blade in front of the tower
causes a noticeable dip in the rotor aerodynamic torque. Furthermore, the rotor has a
strong influence on the tower shedding frequency causing different wake structures
between the upper and the lower parts. The dynamic response of the tower is synchronized
with azimuthal angle of the rotor and the blades suffer oscillatory deformation
particularly in the flapwise direction. This creates cyclic fatigue loads and structure
deformation three times per rotation which are considered to be important for the tower
design and fatigue-life analyse.weiterlesen