Model order reduction of the aeroelastic response of a wind turbine rotor blade

The dynamic response of a wind turbine is mainly governed by the a􏰁ecting 􏰃ow forces of the wind. Concerning life expectancy, the vibration sensitivity of the rotor blades is of particular importance. In this contribution the dynamics of a rotating blade is described including the deformation-dependant aerodynamic forces [1]. Then, a reduced-order model for the coupled system of structure and 􏰃uid 􏰃ow is derived, which is more e􏰄cient concerning the calculation through the use of less degrees of freedom, but maintains the stability characteristics of the non-reduced-order model.
A single rotor blade is described as a straight Bernoulli beam with a variable non-symmetric sectional pro􏰂le. The coordinate system refers to the current position of the blade. Besides the structural sti􏰁ness, mass inertia and aerodynamic loading according to potential 􏰃ow theory are included. The aerodynamic loading is linearised following the Scanlan model described in [2]. The linear equation of motion is formulated by means of the principle of virtual deformation assuming a constant rotational speed [3].
The quality of the model order reduction approach strongly depends on the chosen reduced basis. In this approach the basis is built by an appropriate selection of eigenmodes, which are dependent on the aerodynamic loading and parametrized on the rotational speed of the blade. The contribution discusses available methods [4] of creating reduced bases eligible to correctly represent the 􏰃utter characteristics in a spectrum of operating speeds.