A wind turbine is subject to dynamic loading continuously throughout its life. As the usage of wind power capacity has been dramatically increasing, the structural size and the power output of the wind turbine have also been increasing. Significant technical advances over the last decade have made it possible to capture wind energy more efficiently and to reduce the price of electricity generation. These advances have led to large offshore wind turbines with lighter, more flexible blades with considerably larger blade length. This, however, has introduced significant aeroelastic instabilities, such as blade stall-induced vibrations and flutter, which have resulted in many catastrophic failures of wind turbines.

 

Understanding aeroelastic instability problems requires fluid-structure interaction (FSI) approach considering both aerodynamic and structural part of the wind turbine model. Modern wind turbines are typically designed and analysed with the aid of wind turbine specialist simulation software which is based on Blade Element Momentum (BEM) model due to its advantage of fast computation. However, the BEM model is incapable to provide the detailed flow information, and thus the insight of the flow nature around the wind turbines as well as the aeroelastic characteristics of the wind turbines are limited. The vortex models which employ prescribed-wake method or free-wake method have also been used to study wake dynamics of wind turbines. The vortex models, however, ignore the viscous effects which limits in understanding wind turbine aeroelastic behaviour. Computational Fluid Dynamics (CFD) method, on the other hand, is a very efficient tool for aerodynamic modelling and it has the capability of providing the detailed flow information which makes it possible to study aerodynamics of any structure in details. The major drawback of the CFD approach is that it requires large computational resources. As the computation time is the main challenge, the majority of the studies use low fidelity models or introduce simplicities in the models such as ignoring tower and disregarding the effects associated with the tower. As a result, understanding of interaction between the flow unsteadiness and the wind turbine structure including tower is limited. Therefore, a high fidelity numerical model should be developed to provide understanding of the aerodynamic and aeroelastic problems associated with the complete wind turbine model at a reasonable computational cost.

 

The primary aim of this paper is to develop a high fidelity computational model to analyse the effect of tower on the unsteady flow field around the wind turbine as well as to explore the forced response and flutter instability problems of the complete wind turbine model. The non-linear frequency domain method, which provides a particularly elegant way of modelling harmonic disturbances, has been used for the turbomachinery aeromechanical analysis and flutter predictions of multiple blade row configurations. In the present work, the non-linear frequency domain method will be used for the aerodynamic and aeromechanical analysis of the complete wind turbine model, and this method will be validated against the experiment as well as the conventional time domain method.


Aeromechanical Analysis of a Complete Wind Turbine Using Nonlinear Frequency Domain Solution Method

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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