Numerical investigation of the blocking effect of a short duct on propeller noise

Electric vertical and takeoff/landing vehicles for urban aerial mobility have attracted considerable attention in recent years. Some of these vehicles are equipped with ducted propellers to improve power efficiency, but the duct may also affect propeller noise generation and radiation. This work presents thorough numerical investigations to assess the importance of a short duct on propeller noise radiation. An analytical model is employed to predict noise emission from an isolated propeller, and the boundary element method is adopted to account for acoustic scattering effects. Additionally, an efficient data-clustering method is proposed to accelerate the overall noise prediction process. Parametric studies concerning geometries and the propeller's installation location are performed to exploit the duct's feasibility for low-noise vehicle development. Results suggest that the blocking effect can significantly benefit noise control for different rotating speeds, and installing the propeller at the symmetric plane of the duct can achieve the most noise reduction.