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COBEM 2019
25th International Congress of Mechanical Engineering
GLOBAL DYNAMIC ANALYSIS OF A SPAR WIND TURBINE USING THE NONLINEAR NORMAL MODES
Submission Author:
Gabriel Nicaretta , PR
Co-Authors:
Gabriel Nicaretta, Elvidio Gavassoni
Presenter: Gabriel Nicaretta
doi://10.26678/ABCM.COBEM2019.COB2019-2386
Abstract
The energy demand growth to sustain economic expansion and social development is a major challenge. Wind energy has been increased prominently in the search for renewable energy sources, and is also a reason for studying its untapped potential at offshore areas. In this scenario, floating offshore wind turbines (FOWTs) have been designed to be installed in deep water levels. These facilities are subject to wind and wave loading. Unlike the usual civil construction structures, floating platforms can present significant angular rotations invalidating a linear analysis of the structure. Due to the coupled between the degrees-of-freedom in nonlinear dynamics, it becomes impracticable to use discretization schemes-based programs without large numerical capacity. However, the use of reduced models based on the concept of nonlinear normal modes (NNMs) can be used for a preliminary analysis. The NNMs can be viewed as nonlinear extension of their counterpart linear modes. The invariant manifolds method is used in the work to obtain the reduced order models (ROM) of a NREL 5-MW Baseline Wind Turbine installed on a Spar Buoy platform. ROM are used to study the nonlinear dynamic behavior of the structure. The phase space, frequency-energy and frequency-amplitude curves are obtained for the two nonlinear normal modes of the system. Some nonlinear phenomena such hardening and softening behavior are observed. The ROM results are compared to the benchmark solution, obtained via the numerical integration of the full system of equation of motion. This comparison confirms that the nonlinear normal modes can be used to study the global nonlinear dynamics of the system.
Keywords
offshore structures, Renewable energy sources, Invariant manifold, Floating platforms, Reduced order
