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Article
Mechanics
Siyang Zhong et al.
Summary: This work investigates the aeroacoustic effects of rotational speed deviation, rotation speed fluctuation, blade vibration and blade geometric asymmetry on flying vehicles with pitch-fixed rotors. The analysis shows that periodic rotation speed fluctuations and blade vibrations can produce significant extra tones, while random fluctuations and vibrations increase the noise level in a wide frequency range. The asymmetric blade geometry causes extra tonal noise at the harmonics of the blade shaft frequency. The study also highlights the influence of factors like initial phase difference and rotation directions on the noise features of dual rotors.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jiafeng Wu et al.
Summary: Unmanned aerial vehicles (UAVs) are a significant research topic due to their various applications and potential in meeting future air transportation demands. However, there is limited research on the interaction between rotors and upstream bodies at low Reynolds numbers, which is the operating condition for most small UAVs. In this study, numerical simulations were conducted to investigate the interaction between a rotor and the wake of an airfoil at low Reynolds numbers using a specific simulation method and acoustic analogy. The results showed a close coupling between the axial forces and surface pressure perturbations of the airfoil with the rotor rotation, and the effect of interaction on the rotor blades depended on the relative angle of attack. Additionally, the analysis of surface pressure fluctuations indicated that tonal noise and high-frequency noise were mainly caused by different mechanisms.
Article
Engineering, Aerospace
Orazio Pinti et al.
Summary: This study presents a multifidelity approach that combines the advantages of high-fidelity and low-fidelity models to ensure accuracy while improving computational efficiency. The approach is applied to simulate the lift and drag distributions of a two-rotor assembly, and the results demonstrate a significant improvement over low-fidelity models.
Article
Mechanics
Yan Wu et al.
Summary: This paper presents a detailed investigation of tonal noise generated by an unmanned aerial vehicle propeller with a circular strut mounted downstream. Experimental measurements and computational fluid dynamics simulations were used to analyze the acoustic pressure and the noise generation mechanism. The study showed that the magnitude and shape of the pressure impulse caused by the propeller-strut interaction varied with observer location and decreasing the distance between the propeller and the strut reduced the impulse magnitude. The analysis also revealed that both the propeller and strut contributed to the noise generation, and the combined signals had a complex directivity. Analytical models were developed to estimate the unsteady loading on the propeller and strut and predictions made using these models showed reasonable agreement with experimental and computational results.
Article
Mechanics
Seokbong Chae et al.
Summary: In this study, the effects of rotor-rotor interaction on wake characteristics were experimentally investigated for a twin-rotor configuration in axial descent. The results reveal that the interaction between rotors affects the wake characteristics, especially in the inner region, and the effects vary depending on the descent rate and distance between rotor tips.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Hanbo Jiang et al.
Summary: This work presents and validates a high-efficiency low-noise propeller design for unmanned aerial vehicles, confirming its improvements in aerodynamic efficiency and noise emissions through numerical simulations and experiments.
Article
Engineering, Aerospace
Denis-Gabriel Caprace et al.
Summary: The VTOL aircraft market is booming, and various configurations have an impact on aerodynamics. Studying the interactions through CFD can provide information for developing cheaper numerical models. The study found that the airframe has a certain influence on rotor forces, but its impact on overall aircraft performance can be ignored. However, the rotor-airframe interaction should be considered in predicting airframe loads and wake development.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Mechanics
Vivek Ahuja et al.
Summary: This study integrates established acoustic prediction techniques into a surface-vorticity solver, aiming to enhance the aircraft designer's ability to characterize the acoustic signatures of urban air mobility vehicles, especially distributed electric propulsion concepts. The solver is based on a reliable panel code with viscous boundary-layer corrections, providing a computationally efficient tool for conceptual design and preliminary aerodynamic analysis. By implementing the Farassat F1A acoustics formulation directly into the solver, a new intuitive capability is achieved, compatible with modern engineering tools.
Article
Acoustics
Hanbo Jiang et al.
Summary: This paper investigates the radiation modes and efficiency of propeller tonal noise, formulating models in spherical coordinates. By decomposing the radiation field into spherical harmonics, the analysis can be conducted on sound field structures. The proposed model mathematically explains how thrusts only produce antisymmetric sound waves with respect to the rotating plane, and the decay of radiation efficiency as noise sources approach the rotating center.
JOURNAL OF VIBRATION AND ACOUSTICS-TRANSACTIONS OF THE ASME
(2022)
Article
Engineering, Aerospace
Richard Healy et al.
Summary: This study investigates the aerodynamic interactions of a two-rotor system, showing that the performance of the aft rotor is affected by its proximity to the front rotor. Increasing the vertical rotor separation reduces the interactional aerodynamic effects. Additionally, reducing the rotor disk loading and increasing flight speed both increase the aerodynamic penalties.
JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
(2022)
Article
Engineering, Aerospace
Reda R. Mankbadi et al.
Summary: This study focuses on the broad-band noise generated by an unmanned aerial vehicle's propeller and its propagation characteristics, with simulated results in good agreement with actual data. The emphasis is on analyzing the physical properties of turbulence-generated noise and how it spreads in the acoustic field.
Review
Engineering, Aerospace
G. Throneberry et al.
Summary: This work consolidates and discusses previous studies on wake propagation and flow development of multi-rotor drones, highlighting the importance of in-depth understanding of wake propagation for accurate prediction. Studies have focused on proximity effects using Computational Fluid Dynamics simulations and experimental research to capture multi-rotor wake and flow development.
PROGRESS IN AEROSPACE SCIENCES
(2021)
Article
Engineering, Aerospace
Damiano Casalino et al.
Summary: Experimental and numerical results of a low Reynolds number propeller are presented as a preliminary step towards defining a benchmark configuration for low Reynolds number propeller aeroacoustics. The study identifies the experimental and numerical challenges of the benchmark and the relevance of fundamental research questions related to transition and other low Reynolds number effects.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Acoustics
Romain Gojon et al.
Summary: This study experimentally characterises low Reynolds number rotors in an anechoic room, investigating the noise characteristics of rotors with different numbers of blades. The results show that all noise characteristics increase with rotational speed, and the amplitudes of BPF and its first harmonic are minimal at low rpm and/or high number of blades, while maximal at high rpm and/or low number of blades.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Mechanics
Jie Gong et al.
Summary: The study focuses on investigating the wake dynamics of a ducted propeller using detached eddy simulations, revealing the impacts of blade-blade interference and blade-duct interaction on loading stability and efficiency. Short-wave instability governs the wake, with multi-induction effects and duct characteristics influencing the tip vortex system differently.
Article
Engineering, Aerospace
Tom C. A. Stokkermans et al.
Summary: The paper investigates the performance effects of propeller interactions in side-by-side and one-after-another configurations, showing strong dependency on geometric layout. The experiment found variations in propeller thrust and power penalties based on different configurations.
JOURNAL OF AIRCRAFT
(2021)
Article
Engineering, Aerospace
Sicheng (Kevin) Li et al.
Summary: This paper investigates the broadband noise of multirotor urban air mobility (UAM) VTOL vehicles and finds that high-frequency broadband noise is important where the community background noise level is typically low. It is observed that VTOL designs with more rotors produce higher broadband noise for the same mission specifications. The use of multiple rotors can reduce amplitude modulation and noise annoyance, compared to a single rotor.
JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
(2021)
Article
Computer Science, Information Systems
Seungcheol Lee et al.
Summary: In this study, the effects of rotor-rotor interaction on the wake structure and thrust generation of a quadrotor UAV were experimentally investigated. A modified Landgrebe's model was proposed to accurately describe the impact of interaction on the wake structure. The results show that the inner tip vortex shift away from the rotational axis and the induced axial velocity increase followed by a decrease in the local effective angle of attack are important mechanisms for thrust loss caused by rotor-rotor interaction.
Review
Economics
Suchithra Rajendran et al.
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW
(2020)
Article
Transportation
Anna Straubinger et al.
JOURNAL OF AIR TRANSPORT MANAGEMENT
(2020)
Article
Mechanics
Hakjin Lee et al.
Article
Engineering, Aerospace
Matthew Misiorowski et al.
Article
Remote Sensing
Zhenyu Wang et al.
Article
Engineering, Aerospace
Pooneh Aref et al.
Article
Mechanics
V. L. Okulov et al.
JOURNAL OF FLUID MECHANICS
(2007)
Article
Mechanics
P. R. Spalart et al.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2006)
Article
Computer Science, Interdisciplinary Applications
G Kalitzin et al.
JOURNAL OF COMPUTATIONAL PHYSICS
(2005)
