Flow induced noise reduction design of airfoils with spanwise riblet surface

Airfoils are typical structures applied in many practical engineering applications, such as wind turbines, the wings of airplane, and marine propellers. However, unnecessary noise would be generated when these devices are in operation, which is deleterious both to people nearby and the surrounding environment. In recent decades, several methods are proposed to reduce the flow induced noise, including serrated trailing edge, wavy leading edge, perforation treatment, etc. Though these methods are feasible to some extent, they are still in the stage of academic investigation. To narrow the gap between scientific research and practical engineering, the biomimetic surface, which imitates the surface morphology of living beings in nature, was introduced to airfoils to reduce drag. As an in-depth study, the noise characteristics of the airfoils with spanwise riblet surface are investigated in this paper based on large eddy simulations and acoustic analogy method. The results showed that both flow field and noise field could be improved through rational design. Reasons for noise reduction are the generation of vortices generated in the riblet structures, which is beneficial to the flow field near airfoils and the wake flow. Due to the advantage of concise structures, it is promising to design low-noise airfoils.