The evolution of finlets for aerodynamic noise control: A decade of research from inception to modern applications

Airfoil aeroacoustics has emerged as a significant challenge across various industries, including aviation, renewable energy generation, and marine applications. This article provides a comprehensive and systematic review of finlets as a passive, bio-inspired method for effective trailing-edge noise reduction. Detailed flow physics studies have confirmed that the primary mechanism of finlets in noise reduction is the manipulation of the turbulent boundary layer. These structures lead to a significant reduction in surface pressure fluctuations, vortex convection velocity, and spanwise coherence of turbulent eddies. Analyses show that finlets effectively reduce noise in the mid- and high-frequency ranges by increasing viscous dissipation and stretching turbulent structures. Furthermore, the critical lift-up process moves energetic eddies away from the surface, which in turn reduces their destructive interaction with the trailing edge. This review indicates that three-dimensional configurations (such as staggered or gradually spaced designs) exhibit better performance by more effectively modifying turbulent structures. The article also highlights the successful application of finlets on fixed airfoils and rotating blades, demonstrating the high adaptability of this solution. Despite their proven effectiveness, significant challenges such as the trade-off between noise reduction and aerodynamic performance and the dependence of optimal performance on precise geometric specifications persist, emphasizing the need for targeted optimization for each application. This review concludes that finlets are a promising solution with high research potential, capable of bridging biomimetic innovations and engineering solutions to achieve quieter aerodynamic performance.