Axial flow, common during the operation of urban air mobility vehicles equipped with ducted propellers, can alter the flow features around the propeller and its wake. This study examines the changes in flow characteristics, aerodynamic performance, and noise radiation properties of a ducted propeller with two blades of radius 115 mm under different axial flow speeds and rotational speeds, performing experiments in an anechoic wind tunnel and comparing the results with those of an unducted propeller. Higher axial flow speeds reduce the thrust produced by both components, with the duct experiencing a more rapid reduction. In hover, particle image velocimetry results do not show coherent turbulent structures linked to the tip vortex, but they are present with axial flow, reducing with the advance ratio Formula: see text. The turbulent kinetic energy in the wake decreases with Formula: see text. Compared to the unducted propeller, the coherent turbulent structures are reduced, and the wake turbulent kinetic energy increases. The blade-passing frequency noise decreases with Formula: see text and can be scaled with the component thrust. Broadband noise also reduces with Formula: see text and can be scaled with Formula: see text, where Formula: see text is the Mach number based on the convection velocity, suggesting that it is dominated by the blade’s turbulent boundary-layer trailing-edge noise.
Cantos et al. (Sun,) studied this question.