Modal Analysis of a Vertical-Axis Darrieus Wind Turbine Blade with a Troposkein Shape

Darrieus wind turbines with troposkein shaped blades are an important type of vertical axis wind turbines. When designing these blades it is important to consider vibration properties and how vibrations may affect failure and safe load margins. In order to avoid the occurrence of resonance, the natural frequencies of the blade structure needs to be determined and designed relative to the turbine operating ranges. In this work we examine the modal characteristics of Darrieus style vertical-axis wind-turbine blades. We build a finite element model of a spinning Sandia straight-circular-straight blade, and compare the results of our model with those of Sandia. We then use the model to study the stationary blade, and the blade with a true troposkein blade shape. The modeling of the blades using slender beam theory is sketched for comparison with the finite element model and for its eventual use for low-order modeling.