Aeroacoustics Applications to Jets and Rotors

<p>Aeroacoustics plays a critical role in the advancement of propulsion technologies for both conventional and emerging aerial systems. This dissertation investigates two key topics: noise suppression in supersonic rectangular jets and rotor noise characterization in hover and ground effect. Using high-fidelity numerical simulations and theoretical analyses, this research aims to develop effective noise mitigation strategies and improve predictive methodologies.</p> <p>The first part of this study focuses on the reduction of noise in supersonic rectangular jets through active control techniques. A novel approach utilizing unsteady microjet actuation at the nozzle lip is explored to disrupt the formation of large-scale turbulent structures responsible for noise generation. High-fidelity simulations capture the unsteady flow dynamics and acoustic propagation, revealing how microjets alter the dominant frequency modes of coherent structures. Through Spectral Proper Orthogonal Decomposition (SPOD), the study identifies the impact of actuation on the energy distribution across the frequency spectrum. Results demonstrate a measurable reduction in Overall Sound Pressure Level (OASPL), particularly at peak radiation angles, confirming the potential of microjet-based strategies for adaptive noise suppression in jet propulsion systems.</p> <p>The second focus of this dissertation is on rotor noise characterization, particularly in the context of eVTOL applications. Although the study is limited to a single rotor configuration, it serves as a foundational step toward understanding the aeroacoustic behavior of multirotor systems in Urban Air Mobility (UAM). This research, conducted as part of a NASA University Leadership Initiative (ULI), combines computational and experimental efforts to validate numerical approaches for rotor noise prediction. High-fidelity computational fluid dynamics (CFD) and aeroacoustic solvers are employed to analyze a scaled eVTOL propeller in hover and edgewise flight, out and in ground-effect (IGE) conditions. Results show that ground reflections amplify lateral noise levels due to constructive interference, and modifications in directivity patterns are identified based on observer locations. The study also examines how wake interactions influence acoustic signatures when the rotor is at close proximity to the ground and how the Method-of-Images (MOI) can be utilized to simplify acoustic predictions of ground-effect scenarios.</p> <p>This dissertation advances the development of quieter and more efficient propulsion technologies while also developing reliable numerical tools. The insights from the jet noise suppression study lay the groundwork for future active control strategies, while the rotor noise investigation strengthens predictive methodologies for eVTOL applications, providing accurate tools and frameworks for the research group and the academic community.</p>

Name thesis:degree_name

Doctor of Philosophy in Aerospace Engineering

Level thesis:degree_level

Dissertation - Open Access

Discipline thesis:degree_discipline

Aerospace Engineering

Year

2025

Author dc:creator

• Marques G., Michael

• aeroacoustics
• cfd
• rotorcraft
• supersonic jet
• evtol
• noise prediction
• ffowcs williams–hawkings method
• detached eddy simulation
• ground effect acoustics
• urban air mobility
• propeller noise
• high-fidelity cfd
• acoustic analogy
• permeable surface integration
• tip vortex interaction
• rotor wake dynamics
• experimental validation
• nasa uli
• joby aviation propeller
• farassat’s formulation 1a
• mic array measurements
• pressure fluctuation analysis
• computational aeroacoustics
• evtol performance modeling
• Aerodynamics and Fluid Mechanics
• Aeronautical Vehicles
• Propulsion and Power

Repository record dc:identifier

https://commons.erau.edu/edt/885

OAI identifier oai:identifier

oai:commons.erau.edu:edt-1919