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abstract

  • The idea of simply designing large single wind turbines is an incremental and technological step, which presents challenges in installation and maintenance issues. Another approach, Multi-Rotor Wind Turbine (MRWT) design, is to utilize several wind turbines mounted on a single support structure. The use of MRWTs offers to improve the performance and economic viability when compared with Single Rotors Wind Turbines (SRWTs). However, they present different challenges than traditional designs. When wind turbines are subjected to different loading scenarios this results in the out-of-plane and the in-plane deformations. The resulting rotations and deflections are amplified in MRWT systems due to the interactions between the different rotors. Although finite element methods (FEMs) are deployed to study the structural behavior of MRWT, there is currently a gap in mathematical approach to investigate dynamic behavior of MRWTs under large deformations.
    The development of a mathematical formulation deriving the general governing Equations of Motions (EOMs) and separating the typical linear formulation and the nonlinear contributions, due to large deformation behavior, is quite challenging. The current study will provide a new and demanding mathematical formulation of the governing EOMs for the MRWT systems with any symmetric configuration. In order to illustrate the proposed approach, a building block model (a triangular 3-rotor system) is introduced. The EOMs of several configurations of MRWTs are derived based on the structural behavior of the 3-rotor building block. The current study illustrates the p-delta effects and the significance and contribution of the large displacements-induced nonlinearities for both hypothetical and existing MRWT systems through the numerical solutions to the derived EOMs and FE analyses of the MRWT configurations. More explicitly, the current study shows that, for some degrees of freedom (DOFs), the large displacements-induced nonlinear terms cause noticeable variations in the structural responses of the MRWT systems.