Experimental study of boundary layer turbulence transition and flow separation of wind turbine blades due to leading edge roughness.*

This research aims to characterise the aerodynamics of wind turbine blades with rough leading edges in experiment. This work is motivated by the increasing phenomenon of wind turbine leading edge erosion. Deployed wind turbine blades have been observed to experience deterioration at their leading edge due to impact with rain, hail and particulates. Despite significant research interest, experimental imaging of the boundary layer suitable for validation of numerical models is not found in the literature.

To this end, experiments were carried out to analyse the effects of leading edge roughness on a wind turbine blade geometry using a low-speed wind tunnel. Direct experimental imaging of the boundary layer around the model was captured by non-invasively filling the suction side boundary layer with smoke lit by a continuous wave laser. Then, particle image velocimetry was used to characterise the background turbulence of the wind tunnel and to create vector fields of the leading edge and suction side boundary layer. Analysis has yielded results on the effects of leading edge roughness on boundary layer structures, turbulence transition, flow separation and other data.

This experimental data will be used to validate turbulence modelling and boundary layer roughness approaches and make recommendations for other projects. Specifically, the Langtry-Menter turbulence transition model and associated roughness boundary condition will be validated.