Experimental study on identification of aerodynamic damping matrix for
an operating wind turbine by artificial excitation
Abstract
Quantitation of damping is of great significance for the design and
condition assessment of wind turbines. The authors’ previous theoretical
and numerical studies showed that compared to damping ratios, a modal
aerodynamic damping matrix can better describe the damping coupling in
the fore-aft (FA) and side-side (SS) tower motions. In the present
study, an improved damping identification method was first proposed to
identify this damping matrix with artificial exciters and then verified
by using OpenFAST simulations under different excitation frequencies,
excitation force amplitudes, and different turbulent wind fields.
Following the numerical study, a scaled wind turbine model with a
geometric scale ratio of 1/75 was carefully designed based on the NREL 5
MW wind turbine prototype, in which the scaled blade design follows the
rule in thrust coefficient similarity. An identification study was
performed with this scaled model by a series of wind tunnel tests. The
modal aerodynamic damping matrix was identified under steady-state
harmonic excitation in the operating state and compared with the
identified results by a free decay method and the theoretical values.
The results experimentally confirm the correctness of the aerodynamic
damping matrix theory under uniform wind and the feasibility of the
improved identification method in practice.