A review on flow visualisation of wind turbine blades in operation

For wind turbine blades (WTBs), boundary layer flow detection can help demonstrate their surface condition, indicate their early failures and global deformation, which becomes more important with the increasing number of in-service wind turbines. Compared with fluid dynamics (CFD) methods and blade element momentum (BEM) methods, flow visualisation method is an intuitive method, which can realise an unambiguous measurement of boundary layer flow on real wind turbines. As a result, some flow visualisation methods were proposed and improved by researchers in recent years. A comprehensive review on flow visualisation of wind turbine blades, especially in-service blades, is necessary to enable researchers to better understand this field and analyse the coming research trends. In this paper, flow visualisation methods were introduced, while emphasis was placed on infrared thermography (IRT) approaches. At last, an in-depth analysis of the future trends of IRT flow visualisation methods was given.