A parametric study of serration design for trailing–edge broadband noise reduction

This work discusses the physics of noise reduction achieved from serrated trailing–edges and its impact by the serration design. An experimental campaign is carried out with a benchmark 2D model based on a NACA 63₃–018 airfoil. Different trailing-edge serrations are tested under several flow speeds and angles of attack conditions to build a complete dataset of acoustic measurements. Systematic modifications of a reference sawtooth serration design are made to its scale and geometry. Scale modifications are based on sawtooth serrations and comprehend carefully considered variations of the serration height (2h), wavenumber (λ), and aspect ratio (2h/λ). Geometric shape modifications are represented by concave–shaped and combed–sawtooth serrations. This study represents a unique sensitivity–based parametric analysis on the scaling and geometric properties of trailing–edge serrations where the impacts of each modification are studied separately. The results obtained are used to provide guidelines for serration design choices and their impact on broadband noise reduction.