Reduction of Rotor Noise Using Serrated Blades with Modulated Airfoil Thickness

Previous computational aeroacoustics studies of a hovering ideally twisted rotor demonstrated the presence of new broadband noise sources, trailing-edge vortex shedding (TE-VS) noise and blade secondary vortex interaction (BSVI) noise, yielding high-frequency and mid-frequency noise respectively. Past research has demonstrated and explained the capabilities of implementing a serrated trailing edge to reduce broadband noise for rotary-wing applications, but its effect on TE-VS has not been investigated fully and explained thoroughly. In this work, we employ high-fidelity computational fluid dynamics (CFD) simulations to demonstrate how trailing-edge serrations and modulated airfoil thickness can suppress TE-VS noise with the trade-off of an increase in BSVI noise due to enhanced local three-dimensional flow effects. Ongoing work aims to evaluate the impact of various leading-edge and trailing-edge serration geometries to minimize the overall rotor broadband noise and identify an optimal serrated rotor-blade configuration.