An aeroelastic model for vertical-axis wind turbine blades

This study develops a two-dimensional aeroelastic model for the blades of vertical-axis wind turbines. This model is theoretically traceable and computationally efficient owing to its simple form. The structural dynamics of the blade is reduced to a two-dimensional section with heave and pitch degrees of freedom. The equations of motion are derived using Lagrange's equations. The effects of centrifugal stiffening are added to the model using Southwell's coefficients. Aeroelastic stability is investigated in both the frequency and time domains. Theodorsen's unsteady aerodynamic theory is used in the frequency domain formulation, where the stability analysis is conducted using the standard p-k method. For time domain analysis, a free-wake unsteady vortex lattice method is coupled with the structural dynamics equations using a conventional serial staggered scheme. The root-mean-square of the normalized potential energy of the system is used to pinpoint the onset of flutter. Comparison of flutter speed and frequency from frequency- and time-domain solutions with experimental data shows close agreement, validating the model’s predictive capability. Additionally, a parametric study is carried out to investigate the effects of mass ratio, frequency ratio, and the dimensionless center-of-mass offset from the mid-chord on the flutter speed. These analyses are essential for validating the design of larger and lighter blades currently being developed for offshore wind energy applications.