Experimental study on noise reduction of a wavy multi-copter rotor

Yang, Yongrong; Liu, Yu; Hu, Haitao; Liu, Xiaomin; Wang, Yong; Arcondoulis, Elias; Li, Zhiyong

doi:10.1016/j.apacoust.2020.107311

Cited by 27 publications

(11 citation statements)

References 18 publications

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“…The noise reduction effect was most obvious when the air velocity was 50 m/s and the sound pressure level was reduced by 2.560 dB. Yu Liu et al studied the noise reduction of a wavy multi-copter rotor; the attenuation of total sound pressure level of the wavy rotor with respect to the baseline rotor was about 1.4-2 dB [45]. Aerodynamic and acoustic investigations of multi-copter rotors with trailing edge serrations have been performed.…”

Section: Aeroacoustics and Transmission Loss Analysismentioning

confidence: 99%

Structural Design and Parameter Optimization of Bionic Exhaust Tailpipe of Tractors

et al. 2022

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The exhaust tailpipe of a certain type of tractor was improved from the perspective of bionics, and bionic triangular convex texture was added to the inner surface of the exhaust tailpipe. The bionic tailpipe was proposed to improve noise reduction performance without changing the overall size parameters of the prototype tailpipe. Acoustics simulation software was used to predict the aeroacoustics noise and transmission loss of the exhaust tailpipe. Bionic exhaust tailpipes with triangular textures of different numbers of circumferential columns, height, and top angles were analyzed to study the noise reduction performance. The results showed that the proposed bionic exhaust tailpipes with triangular convex textures reduced the total sound pressure level and improved the transmission loss of the prototype exhaust tailpipe. To increase the transmission loss, a genetic algorithms (GA) optimized back-propagation neural network (BP) was used to optimize the bionic triangular convex texture parameters. By studying the aerodynamic noise reduction mechanism of bionic tailpipes, the research suggested that a secondary vortex appeared near the bionic texture and reduced aerodynamic drag and aeroacoustics noise. In addition, the sound pressure level amplitude nephogram, velocity vector nephogram, and velocity amplitude nephogram of the exhaust tailpipes were analyzed to study the vibration noise reduction mechanism of the bionic tailpipes. Then, the noise reduction performance was experimentally evaluated. The experimental results of the bionics exhaust tailpipes with triangular convex textures were analyzed and compared to that of the prototype tailpipe. The results demonstrated that the bionic exhaust tailpipes were able to attenuate noise.

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Section: Aeroacoustics and Transmission Loss Analysismentioning

confidence: 99%

Structural Design and Parameter Optimization of Bionic Exhaust Tailpipe of Tractors

et al. 2022

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“…Zawodny et al [14] following work from Brentner and Farassat [15] outlined the most common noise sources present in propeller systems, with Blade Vortex Interaction (BVI) noise identified as a special case of unsteady loading noise. BVI noise occurs when the shed tip vortices of a preceding blade impact the following propeller blade [16]. This noise is characterised by high amplitude tonal noise which repeats at the harmonics of the blade passing frequency (BPF) [17].…”

Section: Introductionmentioning

confidence: 99%

“…Carvalho [20] showed theoretically that by using a more efficient sectional airfoil than a stock quadcopter propeller can yield improvements of up to 30% aerodynamic efficiency and 8.9% reduction in power consumption. Yang et al [16] attempted to alleviate propeller noise by modifying a baseline blade to have a wavy planform by shifting its cross section toward the trailing edge. The aerodynamic and aeroacoustic performance of the blade was evaluated experimentally using far-field microphones and a six-axis load cell and compared to the baseline case.…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic and Aerodynamic Characteristics of Propeller Tip Geometries

Hanson

Baskaran

Pullin

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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A series of experiments were conducted in an aeroacoustic wind tunnel facility to investigate the aerodynamic performance and noise characteristics of propellers with various modifications to its tip geometry. A baseline propeller was designed for static hover conditions. The blade was adapted with the intention to reduce, divert or eliminate the blade tip vortex which is responsible for blade vortex interaction noise. All of the propellers were fabricated using advanced additive manufacturing techniques and tested experimentally in both static hover and forward flight modes of operation. The blade thrust and torque, as well as the radiated far-field noise were collected over a range of rotational speeds in static hover and forward flight conditions. Data was also collected at a thrust-matched condition for each tip modification permitting comparison of figure of merit at static hover. Particular attention was given to the 1st blade passing frequency tone and its directivity and magnitude. Various treatments show promise in changing the directivity and reducing the magnitude of this tone. Each of the categories of tip modification; anhedral, swept and tapered show potential in reducing the overall sound pressure levels as well as the blade passing frequency tone while providing the same thrust output as the unmodified blade. Numerical simulations using the SU2 solver were performed on selected tip modifications to provide further insights into the effects of changing the propeller tip geometry while in forward flight conditions. The numerical simulation results correlate well with the experimental data.

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“…The understanding of noise generating mechanisms are paramount during forward flight. Propellers are expected to experience stronger blade vortex interactions during cruising as compared to hovering [7,8]. While numerous works have been performed on small-scale propeller noise, such as found in [9][10][11][12][13][14][15][16][17], most of them involved only single and isolated configuration systems.…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic Performance of Propellers in Turbulent Flow

Jamaluddin

Çelik

Baskaran

et al. 2021

Aiaa Aviation 2021 Forum

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The aerodynamic noise characteristics of propellers in turbulent flow have been investigated experimentally. In this work, the effect of turbulence interactions on the noise signatures and aerodynamic loading of propellers were investigated using a turbulence-generating passive grid with a solidity ratio of 0.35 and a 3D printed NACA 0012 airfoil wing wake. These turbulence generating methods aim to simulate the fluctuating gusty wind in flight and airframe installation effect, respectively. The experiments were conducted at forwarding flight configuration with freestream inflow velocity ranging from 8 m/s to 24 m/s. Six-axis aerodynamic load measurements and far-field acoustic pressure measurements were performed simultaneously. The results show an increasing trend of thrust energy spectra for propeller operating with turbulence interactions in relative to clean laminar inflow. The acoustic spectrum of the propeller is rich in discrete tones and broadband noise. The results indicate that at a frequency band above 1000 Hz, an increase of noise spectra by about 2 dB/Hz for grid turbulence and around 5 dB/Hz to 15 dB/Hz for wing wake cases were recorded. The overall sound pressure level directivity appears to be less affected by the turbulence ingestion at a low rotational speed. However, at higher RPM, the results demonstrate enhanced radiation downstream.

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Experimental study on noise reduction of a wavy multi-copter rotor

Cited by 27 publications

References 18 publications

Structural Design and Parameter Optimization of Bionic Exhaust Tailpipe of Tractors

Structural Design and Parameter Optimization of Bionic Exhaust Tailpipe of Tractors

Aeroacoustic and Aerodynamic Characteristics of Propeller Tip Geometries

Aeroacoustic Performance of Propellers in Turbulent Flow

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