On the reduction of aerofoil-turbulence interaction noise associated with wavy leading edges

An aerofoil leading-edge prole based on wavy (sinusoidal) protuberances/tubercles is investigated to understand the mechanisms by which they are able to reduce the noise produced through the interaction with turbulent mean flow. Numerical simulations are performed for non-lifting at-plate aerofoils with straight and wavy leading edges (de- noted by SLE and WLE, respectively) subjected to impinging turbulence that is synthetically generated in the upstream zone (freestream Mach number of 0.24). Full three-dimensional Euler (inviscid) solutions are computed for this study thereby eliminating self-noise components. A high-order accurate nite-dierence method and artefact-free boundary conditions are used in the current simulations. Various statistical analysis methods, including frequency spectra, are implemented to aid the understanding of the noise-reduction mechanisms. It is found with WLEs, unlike the SLE, that the surface pressure fluctuations along the leading edge exhibit a signicant source cut-o eect due to geometric obliqueness which leads to reduced levels of radiated sound pressure. It is also found that there exists a phase interference eect particularly prevalent between the peak and the hill centre of the WLE geometry, which contributes to the noise reduction in the mid- to high-frequency range.