Abstract:
Based on the drag reduction principle of non-smooth convex surfaces, the optimal parameters of hemispherical convex hull structure were determined by analyzing the flow field characteristics under different structural parameters. On this basis, streamlined convex hulls were defined to explore the differences in drag reduction between the two structures, and the impact of the convex hull structure on wind turbines was analyzed. Numerical simulations were conducted on NACA0012 airfoils with two types of convex hulls and on a wind turbine with hemispherical convex hulls, and their aerodynamic characteristics were analyzed. The study revealed that when the height of the hemispherical convex hull is 0.4% of the chord length, it achieves the best drag reduction, performing well within an angle of attack range of 10° to 16°. The convex hull structure with a spacing ratio of 3 provides the optimal drag reduction effect for the airfoil. Both hemispherical and streamlined convex hull structures achieve the best drag reduction at an angle of attack of 14°, with maximum drag reduction rates of 12.69% and 17.39%, respectively. Compared to the hemispherical convex hull structure, the streamlined convex hull structure has smaller curvature changes in shape, allowing the flow to adhere better at the fluid-object interface, thus reducing the energy consumption of viscous drag. Considering the manufacturing process difficulty and practical application, the optimized convex hull structures were applied to the surface of wind turbine blades. Compared to the original wind turbine, the radius of the energy utilization zone of the wind turbine with convex hull structures increased by 20.68%; The impact of tip vortices on the highspeed flow region was reduced, the distribution of turbulent kinetic energy became more uniform, and under rated conditions, its torque and thrust were increased by 14.72% and 5.41%, respectively. This improved the energy utilization rate and operational stability.