Novel Aerodynamic Damping Identification Method for Operating Wind Turbines

This contribution introduces a novel method to determine the aerodynamic damping for operating wind turbines. Previous research typically estimated the modal damping ratios in the fore-aft and side-side directions as two decoupled degrees of freedom. This can result in misleading results, as the two directions are closely and unconventionally coupled through the wind-rotor interaction. This study proposes the identification of a novel type of aerodynamic damping matrix. This matrix arises from the linearization of the aerodynamic force resultant obtained from blade element momentum theory (blade modes not included). This linearized force is then applied to a beam finite element model of the tower with a lumped mass representing the rotor-nacelle assembly. This decoupled strategy efficiently describes the physics of the system including the coupling between the fore-aft and side-side motions. The identification of the damping matrix is shown to work for simulated wind time data.