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Aeroacoustic Predictions for a Lift-Offset Coaxial Rotor and Urban Air Mobility Aircraft

AMS Seminar Series

Speaker: Henry Jia, University of California, Davis

Presentation

Seminar Slide Deck (PDF-11MB)

Abstract

Rotorcraft noise is generated by complex flow interactions with rotating blades. Although previous research studies have explored noise sources of conventional helicopters, our fundamental knowledge of acoustic characteristics of multi-rotor systems is still limited. This seminar presents the research work on aerodynamically induced noise of modern multi-rotors in military and civil rotorcraft applications: 1) a lift-offset coaxial rotor and 2) Urban Air Mobility (UAM) Aircraft.

The first part of this seminar will highlight the acoustic characteristics of a lift-offset coaxial rotor configuration in high-speed forward flight, which are studied based on a high-fidelity Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) loose coupling approach for the first time. The novelty of this work is to unravel the flow physics and aerodynamically induced noise of a lift-offset coaxial rotor based on first-principles and multi-disciplinary approaches for the first time. It is found that blade-vortex interaction (BVI) and blade-crossover events are the most dominant noise sources of a lift-offset coaxial rotor, and the strength of these noise sources varies with rotor-to-rotor separation distances, lift-offset values, and aircraft speeds.

The second part of this seminar will discuss the noise characteristics of fully electric and hybrid multi-rotor UAM aircraft in forward flight, which are investigated based on high-fidelity CFD simulations with prescribed blade motions. A total of three UAM aircraft configurations are considered for this research: a one-passenger quadrotor, a six-passenger quadrotor, and a six-passenger side-by-side rotor. It is found that blade-vortex interaction (BVI) events are the most dominant noise sources of the three aircraft configurations. The strength of the BVI events is heavily influenced by rotor size and vehicle payloads. The UAM aircraft noise is also compared against similar-sized helicopter noise as well as various urban background noise levels. It is found that the UAM aircraft noise could exceed the community noise level by more than 10 dB, which implies that noise reduction technologies should be pursued to overcome barriers to public acceptance of UAM noise.

Biography

Photo of Henry (Zhongqi) Jia
Henry (Zhongqi) Jia is a Ph.D. candidate from the Mechanical and Aerospace Engineering Department at the University of California (UC), Davis with a specialization in applied rotorcraft aerodynamics and aeroacoustics. Prior to his Ph.D. study, he received his B.S. degree in mechanical and aerospace engineering from UC Davis and his M.S. degree in aerospace engineering from UC San Diego. During his Ph.D., he has been working on aerodynamics and aeroacoustics research of a lift-offset coaxial rotor and electric or hybrid vertical take-off-and-landing vehicles under the guidance of Professor Seongkyu Lee. His research on the coaxial rotor is funded by the Vertical Lift research Center of Excellence (VLRCOE) program of the US Army, Navy, and NASA. Due to his excellence in rotorcraft research, he has received the Vertical Flight Foundation scholarships as a master's degree student in 2017 and as a Ph.D. student in 2019. After graduation, he will be working as a Science and Technology Corporation contactor for the Computational Aeromechanics Technical Area in the Army's Technology Development Directorate at Moffett Field, CA.