Height-Dependent Rotor Noise and Thrust in Urban Air Mobility: An Experimental Study

TL;DR

This experimental study examines how rotor height and upstream obstructions affect noise and thrust in urban air mobility, revealing that higher placement can reduce noise and improve efficiency.

Contribution

It provides new insights into the impact of rotor height and obstructions on noise and performance, extending beyond previous axial inflow studies.

Findings

Lower rotor heights increase broadband noise due to turbulence.

Higher rotor positions can improve thrust and reduce noise.

Obstruction effects vary with height and flow conditions.

Abstract

The present study investigates the aerodynamic and aeroacoustic characteristics of a propeller operating under varying rotational speeds (RPM) and heights ("H" ), with a particular focus on the effects of upstream obstruction modelled as a tall building. Unlike previous studies that primarily examined rotor noise under axial inflow conditions, this work explores how vortex shedding and flow ingestion from different elevations influence rotor performance and noise emissions. Experiments were carried out in an anechoic wind tunnel, where a tall cylinder was positioned above the propeller to replicate real-world obstruction scenarios. Results revealed that lower propeller heights led to increased broadband noise due to intensified turbulence interactions and reduced aerodynamic efficiency, while higher positions improved thrust performance and mitigated noise effects under certain conditions. The findings contribute to understanding noise sources in eVTOL propulsion systems and provide insights for optimizing propeller placement to enhance aerodynamic efficiency and noise reduction in urban environments