Experimental Aeroacoustics Investigation of Propellers with Turbulence for UAM Application

Abstract

The emergence of electric vertical take-off and landing (eVTOL) aircraft in the Urban Air Mobility (UAM) industry has amplified the need to address noise concerns associated with their operation. The present study aims to analyse the impacts of turbulence ingestion on the aerodynamic performance of rotating blades and the aeroacoustic characteristics. Using small-scaled fixed-pitch propellers, several operational and configurational settings were assessed. An isolated tilting rotor rig was designed and used to conduct a wide range of studies, revealing insights into the aerodynamic loading conditions, the flow field, and the characteristics of sound radiated to the surrounding far field. A load cell transducer was used to determine the loading conditions of the propeller, while arrays of microphones were used to measure the far-field acoustics pressure. Subsequently, flow measurement techniques such as Constant Temperature hot-wire Anemometry, and Particle Image Velocimetry were performed to establish the correlation between the flow interactions and aerodynamic noise. The analyses identified novel insights based on several key influencing factors, including rotational speed, freestream velocity, turbulence interactions and tilting angle. Two primary areas of interest were addressed: (i) the effect of blade pitch and turbulence ingestion on propellers in axial inflow conditions and (ii) the impact of turbulence ingestion on rotors in edgewise inflow conditions. Various tests were conducted in the aeroacoustics wind tunnel to investigate these aspects. The results identified several important factors related to propeller-flow interactions and turbulence ingestion relevant to the aerodynamic loading and noise characteristics. These insights are of great importance for a better understanding of the phenomena and are essential in managing the potential turbulence-induced noise in many eVTOL applications. The study suggested a few practical approaches related to the design of propeller blades and operational boundaries for effective noise control and aerodynamic performance during the operation.

Date of Award	23 Jan 2024
Original language	English
Awarding Institution	University of Bristol
Sponsors	Majlis Amanah Rakyat Malaysia
Supervisor	Djamel Rezgui (Supervisor) & Mahdi Azarpeyvand (Supervisor)