Modelling the aeroelastic response of slender structures to vortex-induced vibrations: Industry transfer through full-scale experimental campaign at a wind turbine

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In this project, wind, force and structural response measurements are carried out in field tests on a wind turbine and the developed aeroelastic model according to the preceding proposal is transferred to the natural scale. During vortex excitation of slender structures, an aeroelastic interaction occurs in the lock-in region. In research, it is modelled as negative aeroelastic damping. This approach has been taken up by preceding proposal and implemented in a fundamental vortex excitation model. The modelling has been accompanied by wind tunnel experiments. Through experimental verification, theoretical deficits in the modelling of the maximum oscillation amplitude can be eliminated and the stress oscillations that are decisive for the design-relevant fatigue processes can be predicted much more realistically and transparently than was previously possible. In this transfer project, it is planned to carry out field measurements on the prototype of the 155 m high wind turbine SG14 as part of the cooperation with the application partner Siemens Gamesa Renewable Energy. The prototype is located at the Østerild wind turbine test field in Denmark. The following quantities will be measured: 1) wind speed profile and wind direction using a meteorological mast, 2) wind pressures at the tower of the wind turbine with 15° angular spacing at each of the two levels, from which wind forces can be integrated, 3) accelerations along the height and 4) strains of the tower wall to determine bending moments at the base and at hub height. The research aims at transferring the concept of aeroelastic modelling in vortex-induced vibrations developed in the preceding project to the reality of transcritical Reynolds numbers, multiple eigenmodes of the structure and realistic turbulent inflow profiles. The reliable determination of the modal parameters (natural frequencies, natural modes and damping ratios) of the structure is thereby co-decisive in order to be able to realistically predict the vortex-induced vibrations when using the developed aeroelastic model. The solution of the inverse problem of system identification is determined on the basis of the response measurements and with the help of Operational Modal Analysis. Furthermore, the distinguished feature at the base of this project is to complement the characterisation of the structural response by an in-depth investigation of the wind forces obtained from simultaneous pressure measurements on the tower surface. As a result, the investigations enable the development of a concept for an industry standard for the response calculation of chimneys, towers, masts and other slender structures that are sensitive to vortex-induced vibrations.