Riblets and scales on 3D-printed wind turbine blades: Influence of surface micro-patterning properties on enhancing aerodynamic performance

Surface textures that can be observed on certain natural elements, such as rice leaves, butterfly wings, shark skins, or fish scales, have inspired manufacturing of 3D-printed wind turbine blades by embedding riblets and scales to enhance the aerodynamic performance. In this study, the characteristics of the blade surface are varied by changing the 3D printing parameters (e.g., precision, layer height, and printing direction) to quantify their effects on the power and thrust coefficients of the wind turbine rotor through wind tunnel experiments. Interestingly, the change in the 3D printing parameters significantly affects the aerodynamic performance of the wind turbine rotor. Specifically, all blade models with riblets show enhanced stall performance compared to the baseline case, with greater improvements by decreasing the layer height. However, for low-precision 3D printing systems, small layer heights can result in the generation of random roughness rather than riblet or scale patterns, thus leading to significant degradation in the aerodynamic performance. The fish scale-like surfaces exhibited the highest energy efficiency with an increase of up to 78% in the power coefficient at the highest tip speed ratio tested for the rotor model.