Aeroelastic Analysis of Horizontal Axis Wind Turbine Based on Multi-body Model

Abstract

The alternate loads like aerodynamic loads, inertial force and elastic force can lead to the coupled vibration of flexible wind rotor, tower and other components, and this coupled vibration can dramatically affects the aerodynamic characteristics and service life of wind turbine. The establishment of aeroelastic coupling mathematical model of horizontal axis wind turbine and its numerical integration method are studied. The super-element(SE) which can describe elastic deformation is used to distretize the flexible component into a series of rigid bodies connected by rotational joints with force element springs and dampers. The dynamic equations of a constrained multi-body system(MBS) of wind turbine is automatically set up and numerically solved through a designed simulation program based on the theory of dynamics of multi-body system and the modelling method of hybrid multi-body system(HMBS). The analysis of dynamic characteristics of the system is realized through Fourier spectrum analysis method. The natural frequencies and modal shapes of a 5 MW offshore wind turbine of United States National Renewable Energy Laboratory(NREL) are analyzed and the effectiveness of the program and the correctness of the modeling method are verified. Aerodynamic loads acting on each rigid body of blade under deformation state are calculated based the blade element momentum(BEM) theory, and the coupling between the structural and aerodynamic analysis is carried out in real time during the process of numerical integration. The results show that super-element can accurately describe the coupling among the aerodynamic loads, inertial loads and elastic loads of wind turbine. The program developed in this study is a useful analysis platform for the aeroelastic coupling, stability analysis and the design of control system of wind turbine.