Design of Flexible Wind Tunnel Model of Yawed Wind Turbine Rotor with Teetering Hub

Abstract

The present study regards a novel wind turbine design featuring a two-bladed rotor on a teetering hub and a yawed tower. A reduced order modelling methodology is proposed for the equation of motion, using a lumped parameter approximation to derive expressions for the structural, rotordynamic and geometric stiffness terms. The analytical expressions are validated numerically. In addition, a methodology is developed for aeroelastic scaling of the rotor for use in wind tunnel tests. This results in two blade design templates, a "stiff" and a "flexible" design focusing on the vibration behaviour and deflected shapes respectively. The templates are designed to be 3D-printable as a single part. Design optimisation was performed in MSC Nastran, yielding two rotor designs, each aiming to match the non-dimensional parameters of interest. The stiff rotor matches the flapwise and torsional natural frequencies within 2.7% error, but has a mismatch in the edgewise mode, as well as the modeshapes and anti-symmetric modes. The flexible rotor is capable of capturing the target normalised displacement profile, at reduced structural mass, partially alleviating the mismatch in Lock number.