In the quest to make urban air mobility (UAM) a viable solution for city congestion, researchers are tackling one of the biggest hurdles: noise. A recent study published in ‘Aerospace Research Communications’ (which translates to ‘Aerospace Research Communications’ in English) sheds light on how dual-rotor systems could help mitigate the noise problem, offering potential benefits that might even ripple out to maritime sectors.
The study, led by Ziang Chai from the Research Institute of Aero-Engine at Beihang University in Beijing, China, focuses on the noise generated by dual rotors in hover conditions. The team used large eddy simulation (LES) to model the flows and the Ffowcs Williams–Hawkings (FW-H) acoustic analogy to predict noise. Their findings are quite intriguing.
Chai and his team found that introducing a phase difference of a quarter of the rotation period between the dual rotors can significantly alter the interaction of vortices in the wakes, particularly the tip vortices. This phase difference also changes the spatial distribution and directivity of noise propagation. The most notable result? The primary tonal noise at the first blade passing frequency is completely counteracted underneath the rotors.
“Although a penalty to increase 3∼4 dB(A) also arises in oblique directions, the resultant noise is still low because of the original insignificant levels,” Chai explained. This means that while there’s a slight increase in noise in some directions, the overall noise levels remain low, offering a promising solution for noise mitigation.
For maritime professionals, the implications could be significant. As urban air mobility systems evolve, they might eventually integrate with maritime transport hubs, such as ports and harbors. Reducing noise pollution from these systems could make them more acceptable in densely populated coastal areas. Moreover, the principles behind dual-rotor phase synchronization could potentially be applied to maritime propulsion systems, offering new avenues for noise reduction in ships and submarines.
The study highlights the potential of rotor phase synchronization in directional noise mitigation for dual-rotor systems. As Chai puts it, “The study shows that the rotor phase synchronization has important potential in the directional noise mitigation for dual-rotor systems.” This could pave the way for quieter, more efficient urban air mobility solutions, benefiting both urban and maritime environments.
In the broader context, this research is a step towards making UAM a practical reality. As the technology matures, it could revolutionize urban transportation, potentially integrating with maritime sectors to create a more connected and efficient transport network. The findings published in ‘Aerospace Research Communications’ offer a glimpse into the future of urban air mobility and the role that noise mitigation will play in its success.