Finite element analysis of wind turbine blade vibrations

The article is devoted to the practical problem of computer simulation of the dynamic behaviour of horizontal axis wind turbine composite rotor blades. This type of wind turbine is the dominant design in modern wind farms, and as such its dynamics and strength characteristics should be carefully studied. For this purpose, in this paper the mechanical model of a rotor blade with a composite skin possessing a stiffener was developed and implemented as a finite element model in ABAQUS. On the basis of this computer model, modal analysis of turbine blade vibrations was performed and benchmark cases for the dynamic response were investigated. The response of the system subjected to a uniform underneath pressure was studied, and the root reaction force and blade tip displacement time histories were obtained from the numerical calculations conducted

Approximate mode-based simulation of composite wind turbine blade vibrations using a simplified beam model

It is well-known that lower modes of vibration are responsible for a high percentage of the dynamic response. In this paper, the task of simulation of the dynamic response of the composite wind turbine blade on the basis numerical realisation of a developed low dimensional beam type model is considered. From the governing system of differential-algebraic equation of the simplified beam type model of the blade, and using the mode superposition approximation, the system of linear ordinary differential equations with respect to the coefficient functions of the modal representation was obtained. The developed program codes allow to simulate low frequency bending vibrations of wind turbine blades under different steady-state and transient loadings. The comparison of the simulation results obtained by the proposed simplified blade model with the results of the direct Finite Element Method (FEM) simulation shows their close agreement, which confirms the adequacy of the developed model and its mode-based approximation to the level of the requirements necessary in engineering practice. The presented approach to the creating low-dimensional simplified models of slender structures can therefore be useful in different fields of aerospace, civil, mechanical, and transport engineering

Nonlinear vibrations in homogeneous non-prismatic Timoshenko cantilevers

Deep cantilever beams, modelled using Timoshenko beam kinematics, have numerous applications in engineering. The present study deals with the nonlinear dynamic response in a non-prismatic Timoshenko beam characterized by considering the deformed configuration of the axis. The mathematical model is derived using the extended Hamilton’s principle under the condition of finite deflections and angles of rotation. The discrete model of the beam motion is constructed based on the finite difference method (FDM), whose validity is examined by comparing the results for a special case with the corresponding data obtained by commercial finite element (FE) software ABAQUS 2019. The natural frequencies and vibration modes of the beam are computed. These results demonstrate decreasing eigenfrequency in the beam with increasing amplitudes of nonlinear oscillations. The numerical analyses of forced vibrations of the beam show that its points oscillate in different manners depending on their relative position along the beam. Points close to the free end of the beam are subject to almost harmonic oscillations, and the free end vibrates with a frequency equal to that of the external force. When a point approaches the clamped end of the beam, it oscillates in two-frequency mode and lags in phase from the oscillations of the free end. The analytical model allows for the study of the influence of each parameter on the eigenfrequency and the dynamic response. In all cases, a strong correlation exists between the results obtained by the analytical model and ABAQUS, nonetheless, the analytical model is computationally less expensive