An exploratory study of the suitability of a wind turbine blade as a nonlinear demonstrator

Nonlinearity can be naturally observed in many applications, but despite this, most engineering systems are designed to be linear. Under certain excitation conditions, even structures which are designed to behave in a linear way, exhibit nonlinearities, which may cause severe complications to their normal operation. The Engineering Nonlinearity (ENL) project is a collaboration among five UK Universities, and is mainly concerned with the understanding of nonlinearities, and the creation of nonlinear design tools which can be used by engineers during the design of structures. As such, it requires the presence of nonlinear structures, or systems which behave in a nonlinear way, to be used as a proof of concept. This paper presents an exploratory study of the suitability of a wind turbine blade as a nonlinear demonstrator. The blade is part of an actual Skystream 3.7 wind turbine, and although it generally behaves in a linear way under low excitation, it is shown that under certain conditions it exhibits weak nonlinearities mainly due to its non-symmetric geometry, and also its material. The use of an FE model is also employed in the effort to understand better the underlying behaviour of the structure.