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Experimental Investigation of the Unsteady Noise Sources Generated by a UAM Rotor in Forward Flight.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Experimental Investigation of the Unsteady Noise Sources Generated by a UAM Rotor in Forward Flight./
Author:	Goldschmidt, James D.
Description:	1 online resource (227 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
Contained By:	Dissertations Abstracts International85-04B.
Subject:	Aerospace engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9798380606837

Experimental Investigation of the Unsteady Noise Sources Generated by a UAM Rotor in Forward Flight.
Goldschmidt, James D.

Experimental Investigation of the Unsteady Noise Sources Generated by a UAM Rotor in Forward Flight. - 1 online resource (227 pages)

Source: Dissertations Abstracts International, Volume: 85-04, Section: B.

Thesis (Ph.D.)--University of Florida, 2023.

Includes bibliographical references

The future of Urban Air Mobility (UAM) presents a promising reality, where daily large-scale air taxi operations will be achieved using electric vertical take-off and landing vehicles (eVTOL). UAM rotors have fixed-pitch blades and operate with low tip speeds, so that the noise they produce is dominated by tonal unsteady loading and broadband noise sources. The goal of the experiments in this study was to reveal physical reasoning's for the force and noise trends seen in these new rotor flight conditions.Experiments were performed on a proposed fixed wing eVTOL configuration, including a two-blade lifting and five-blade tilting rotor, both independently and in tandem with and without installation hardware. Simultaneous rotor force and far field noise measurements were obtained in the University of Florida Anechoic Wind Tunnel facility. The single rotor results showed that the forces were a function of the edgewise advance ratio. The tonal noise indicated an unsteady loading noise source. While, the broadband sources were blade wake interaction noise for frequencies below 30 blade pass frequency harmonics and trailing edge noise above 30 blade pass frequency harmonics. The magnitude and priority of these broadband noise sources also varied with edgewise advance ratio. The overall sound pressure level of the lift rotor was dominated by tonal noise and the tilt rotor was dominated by broadband noise.The isolated tandem rotor configuration produced force trends which were similar to the single rotor experiments, with the lift rotor forces also being dependent on the path of the tilt rotor wake. The wing and boom altered the forces with respect to the isolated configuration. The isolated tandem rotor noise had similar trends to the single rotor experiments, with the possibility of additional blade vortex interaction noise. The overall sound pressure level of the tandem rotor configuration was dominated by the lift rotor tonal noise.Based on the observed noise trends, stereoscopic Particle Image Velocimetry was employed to measure the inflow and wake velocities of a single two-blade rotor in edgewise flight. The inflow measurements were used for unsteady force modeling and analytical tonal blade pass frequency noise predictions, which were accurate to +/- 2 dB below the rotor plane. The wake measurements revealed an asymmetric distribution of wake vorticity, with greater advancing side levels than retreating side levels. Proper Orthogonal Decomposition analysis of the wake revealed coherent turbulent structures, which are key to the rotor wake decay.A two-blade rotor was analyzed in edgewise flight using both clean and turbulent freestream flow conditions. The turbulence had minimal effects on rotor noise, but acted to reduce rotor efficiency. Through stereoscopic Particle Image Velocimetry, it was found that the rotor distorted the freestream turbulence creating a non-homogeneous field with elevated levels on the downstream edge of the rotor disk.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798380606837Subjects--Topical Terms:

686400
Aerospace engineering.
Subjects--Index Terms:

Fluid-dynamicsIndex Terms--Genre/Form:

554714
Electronic books.

Experimental Investigation of the Unsteady Noise Sources Generated by a UAM Rotor in Forward Flight.
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504 $a Includes bibliographical references
520 $a The future of Urban Air Mobility (UAM) presents a promising reality, where daily large-scale air taxi operations will be achieved using electric vertical take-off and landing vehicles (eVTOL). UAM rotors have fixed-pitch blades and operate with low tip speeds, so that the noise they produce is dominated by tonal unsteady loading and broadband noise sources. The goal of the experiments in this study was to reveal physical reasoning's for the force and noise trends seen in these new rotor flight conditions.Experiments were performed on a proposed fixed wing eVTOL configuration, including a two-blade lifting and five-blade tilting rotor, both independently and in tandem with and without installation hardware. Simultaneous rotor force and far field noise measurements were obtained in the University of Florida Anechoic Wind Tunnel facility. The single rotor results showed that the forces were a function of the edgewise advance ratio. The tonal noise indicated an unsteady loading noise source. While, the broadband sources were blade wake interaction noise for frequencies below 30 blade pass frequency harmonics and trailing edge noise above 30 blade pass frequency harmonics. The magnitude and priority of these broadband noise sources also varied with edgewise advance ratio. The overall sound pressure level of the lift rotor was dominated by tonal noise and the tilt rotor was dominated by broadband noise.The isolated tandem rotor configuration produced force trends which were similar to the single rotor experiments, with the lift rotor forces also being dependent on the path of the tilt rotor wake. The wing and boom altered the forces with respect to the isolated configuration. The isolated tandem rotor noise had similar trends to the single rotor experiments, with the possibility of additional blade vortex interaction noise. The overall sound pressure level of the tandem rotor configuration was dominated by the lift rotor tonal noise.Based on the observed noise trends, stereoscopic Particle Image Velocimetry was employed to measure the inflow and wake velocities of a single two-blade rotor in edgewise flight. The inflow measurements were used for unsteady force modeling and analytical tonal blade pass frequency noise predictions, which were accurate to +/- 2 dB below the rotor plane. The wake measurements revealed an asymmetric distribution of wake vorticity, with greater advancing side levels than retreating side levels. Proper Orthogonal Decomposition analysis of the wake revealed coherent turbulent structures, which are key to the rotor wake decay.A two-blade rotor was analyzed in edgewise flight using both clean and turbulent freestream flow conditions. The turbulence had minimal effects on rotor noise, but acted to reduce rotor efficiency. Through stereoscopic Particle Image Velocimetry, it was found that the rotor distorted the freestream turbulence creating a non-homogeneous field with elevated levels on the downstream edge of the rotor disk.
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653 $a Urban Air Mobility
653 $a Rotor disk
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