Frequencies Analysis of a Segmented Wind Turbine Blade in Presence of Uncertainty

Abstract

Wind turbine blades structures must be well balanced during the manufacturing and mounting processes in order to avoid the imbalance of the system and the undesirable dynamic effects during the rotor motion. This work presents a numerical frequencies analysis of a segmented wind turbine blade assembled with a steel spar in order to study the effects of the assembling load, considered as a uncertainty parameter, on the wind turbine rotor balance. For this purpose, the finite beam element was adopted to model the blade segments and the spar structures. The additional assembly stiffness caused by segments assembly load was considered in the developed numerical model. In this work, a deterministic analysis was established to study the influence of the applied load on the assembled blade natural frequencies. Furthermore, a stochastic approach was proposed, based on the Monte Carlo method considering the assembly load as a random variable, to discuss their influences on the wind turbine rotor balance. This study, highlights the significant influence and the importance of the assembly load adjustment on the segmented blade dynamic behavior and thus on the wind turbine life cycle. Thus, the wind turbine rotor must be equipped with a mechatronic system to ensure the blades behavior readjustment during the rotor motion.