Effect of Tip Clearance on Aeroacoustic Noise and Aerodynamic Performance of Ducted Propeller

In this study, the effects of tip clearance on the aerodynamic and aeroacoustic performance of a ducted propeller are systematically investigated through numerical simulations and experimental validation. Steady-state simulations using the moving reference frame (MRF) method and transient simulations employing the sliding mesh method are conducted to analyze both aerodynamic performance and aeroacoustic noise. The velocity contour analysis shows that reducing the tip clearance effectively suppresses tip leakage flow, leading to increased axial core velocity and improved thrust generation. However, transient simulations and Ffowcs Williams-Hawkings (FW-H) based acoustic analyses indicate that smaller tip clearance intensifies blade-vortex interactions (BVI), resulting in elevated low-frequency impulsive noise levels, particularly in forward receiver positions. Experimental measurements of thrust and noise spectra are performed to validate the simulation results, showing good agreement in overall trends. The findings highlight a distinct trade-off between aerodynamic efficiency and noise reduction depending on tip clearance variation. Therefore, careful optimization of tip clearance is essential to balance aerodynamic performance and noise mitigation for practical ducted propeller applications, especially in UAV operations where noise is a critical factor.