Session: 09-01-01 Installation, Marine Operations and Maintenance - 1

Paper Number: 79081

79081 - A Three Degrees of Freedom Vibration Model for a Partially Installed Wind Turbine 

Most offshore wind turbines are installed using the so-called “single blade installation” procedure. This means that after the tower, nacelle and hub are installed, the rotor blades are mounted individually. This process step is difficult and sometimes leads to delays because relative motions between hub and rotor blade need to be small and predictable to enable the successful mounting of the blade. Previously published measurements showed that the tower vibrates in a motion where the nacelle moves in “orbits” that often change shape and axis direction. In this work, we present a simple vibration model that captures some characteristics of the tower dynamics. The model represents the tower and the nacelle as two planar rigid bodies that are connected with a torsional spring. It has three degrees of freedom: the first body’s motion in x- and y-direction and the second body’s rotation around the first body. Thus, its dynamics can be described with three equations of motion. For some configurations of the parameters that describe mass distribution, stiffness, and geometry, the model produces orbits that change in shape and direction even without external forcing. For other configurations, however, the tower vibrates in a stationary orbit. To better understand this behavior, we analyzed what causes a configuration to be stable or unstable. Finally, we discuss which aspects of real turbine dynamics the model describes successfully and which not.

Presenting Author: Andreas Haselsteiner University of Bremen, BIK, BIBA

Authors:

Andreas Haselsteiner University of Bremen, BIK, BIBA
Aljoscha Sander University of Bremen
Klaus-Dieter Thoben University of Bremen