In this paper, aeromechanical analysis of wind turbines is presented. The distinctive feature of this paper is the use of frequency based non-linear harmonic method which is an efficient computational method to study unsteady periodic flow and aeroleasticity of turbomachinery applications, and extensive validation of the non-linear harmonic method against conventional time domain solution methods. This paper is an extension of the authors’ previous work which analysed the aerodynamics of the MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine. Aeromechanical analysis of the MEXICO-Experiment wind turbine as well as 1.5 MW wind turbine are conducted in this study. Both conventional time domain solution method and non-linear harmonic method are used, and compared to each other for validation and verification of the non-liner harmonic method. Using the same numerical set-up for each method demonstrates the differences and capabilities of each solution method, and their computational expenses. Finally, this paper concludes with how the aeromechanical analysis of large wind turbines can be performed effectively and efficiently using the non-linear harmonic method.

This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.

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The aerodynamic simulations of wind turbines are typically carried out using a steady inflow condition. However, the aerodynamics and aeroelasticity of wind turbine blades can be significantly affected by inflow wakes due to the environmental conditions or the presence of neighbouring wind turbines. In this paper, the effects of flow unsteadiness on the aerodynamics and aeroelasticity of the wind turbine rotor are investigated. It is found that the unsteadiness of the wake can have an impact on the aerodynamic flow field around the wind turbine rotor and it could also influence the aeroelasticity of the wind turbine. One of the distinctive features of this paper is the application of the highly efficient nonlinear frequency domain solution method for modelling harmonic disturbances for the aerodynamic and aeromechanical analysis of wind turbines. A test case wind turbine is selected for the aerodynamic and aeromechanical analysis as well as for the validation of the method used. The effects of different material properties along with a large vibration amplitude on the aeroelasticity parameter known as aerodynamic damping of the wind turbine blade are also investigated in the present work. Compared to the conventional time domain solution methods, which require prohibitively large computational cost for modelling and solving aerodynamics and aeroelasticity of wind turbines, the proposed frequency domain solution method can reduce the computational cost by one to two orders of magnitude.

The high-fidelity computational fluid dynamics (CFD) simulations of a complete wind turbine model usually require significant computational resources. It will require much more resources if the fluid-structure interactions between the blade and the flow are considered, and it has been the major challenge in the industry. The aeromechanical analysis of a complete wind turbine model using a high-fidelity CFD method is discussed in this paper. The distinctiveness of this paper is the application of the nonlinear frequency domain solution method to analyse the forced response and flutter instability of the blade as well as to investigate the unsteady flow field across the wind turbine rotor and the tower. This method also enables the aeromechanical simulations of wind turbines for various inter blade phase angles in a combination with a phase shift solution method. Extensive validations of the nonlinear frequency domain solution method against the conventional time domain solution method reveal that the proposed frequency domain solution method can reduce the computational cost by one to two orders of magnitude.