Numerical and Experimental Analysis of Synchronized Propellers for Noise Mitigation

This study investigates the potential of phase synchronization to attenuate the sound power radiated from multiple Distributed Electrical Propulsion (DEP) configurations under forward flight conditions. Adopting a combined experimental and numerical approach, the research aims to analyze how synchronized propellers influence sound radiation, with a particular focus on the far-field tonal noise and its dependence on the blade phase offset between propellers. A noise prediction model introduced in this paper is applied to accurately capture sound trends for various cases of relative phase angles, between adjacent propellers. Acoustic measurements were conducted in an aeroacoustic wind tunnel using a DEP configuration experimental rig, which allows adjusting the relative phase angles of two-bladed propellers from Δ�� = 0° to Δ�� = 90°. The experiments and numerical simulations were conducted at an advance ratio of J=0.63 and a constant propeller rotation rate of 5000 rpm, where a sound reduction of up to 20 dB was observed at the optimal relative phase angle ofΔ�� = 90°, compared to the relative phase of Δ�� = 0°. The impacts of relative phases on aerodynamic performance were found to be negligible, revealing that the noise reduction achieved is primarily due to acoustic interference. These changes are primarily attributed to far-field acoustic interactions, specifically destructive interference between the radiated noise from the propellers, which significantly diminishes the radiated power. This research confirms that phase synchronization is an effective strategy for noise reduction in DEP systems, leveraging the principle of destructive interference to create a quieter environment without compromising aerodynamic efficiency.