scholarly journals A Novel Aerodynamic Noise Reduction Method Based on Improving Spanwise Blade Shape for Electric Propeller Aircraft

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yuhang Wu ◽  
Yan-ting Ai ◽  
Wang Ze ◽  
Tian Jing ◽  
Xiang Song ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Sound Pressure ◽  
Reduction Method ◽  
Dominant Role ◽  
Simulation Method ◽  
Noise Spectrum ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Noise ◽  
Distribution Law ◽  
Blade Shape

Aiming at the problem of excessive propeller noise in a new type of electric aircraft, in order to ensure the propeller aerodynamic characteristics simultaneously, a noise reduction method for improving the shape of the blade along the spanwise is proposed. The FW-H model, the unsteady slip mesh, and the large eddy simulation method are investigated to obtain the aerodynamic noise spectrum. Initially, through propeller aerodynamic noise numerical simulation, we obtain the sound pressure and aircraft aerodynamic noise in frequency domain. Subsequently, the effectiveness of our method is verified by comparing the experimental data and numerical results. Based on the established calculation model and method, under three different rotation speeds, the distribution law of the sound pressure level of the propeller with different shapes along the spanwise is analyzed, and the influence of the blade shape on the aerodynamic noise of the propeller is obtained. The research shows that the aerodynamic noise of the new blade compared to the original blade is significantly reduced at the same rotation speed higher than 1000 rpm, indicating that the blade load noise plays a dominant role in the aerodynamic noise and can be effectively reduced by changing the blade shape along the spanwise, thus reducing the aerodynamic noise of the blade.

Noise Reduction Analysis of Electronic Device Cooling Fan With Duct and Its Application Under Variable Working Conditions

2021 ◽  
Author(s):  
Zonghan Sun ◽  
Jie Tian ◽  
Grzegorz Liśkiewicz ◽  
Zhaohui Du ◽  
Hua Ouyang
Keyword(s):  
Noise Reduction ◽  
Working Conditions ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Reduction Method ◽  
Axial Flow ◽  
Pressure Level ◽  
Inlet Flow ◽  
Cooling Fan ◽  
Inlet Duct

Abstract A noise reduction method for axial flow fans using a short inlet duct is proposed. The pattern of noise reduction imposed by the short inlet duct on the axial flow cooling fan under variable working conditions was experimentally and numerically examined. A 2-cm inlet duct was found to reduce tonal noise. As the tip Mach number of the fan increased from 0.049 to 0.156, the reduction in the total average sound pressure level at 1 m from the fan increased from 0.8 dB(A) to 4.3 dB(A), and further achieved 4.8 dB(A) when a 1-cm inlet duct was used. The steady computational fluid dynamics (CFD) showed that the inlet duct has little effect on the aerodynamic performance of the fan. The results of the full passage unsteady calculation at the maximum flow rate showed that the duct has a significant influence on the suction vortexes caused by the inlet flow non-uniformity. The suction vortexes move upstream to weaken the interaction with the rotor blades, which significantly reduces the pulsating pressure on the blades. The sound pressure level (SPL) at the blade passing frequency (BPF) contributed by the thrust force was calculated to reduce by 36 dB at a 135° observer angle, reflecting the rectification effect of the duct on the non-uniform inlet flow and the improvement in characteristics of the noise source. The proper orthogonal decomposition (POD) of the static pressure field on the blades verified that the main spatial mode is more uniformly distributed due to the duct, and energy owing to the rotor-inlet interaction decreases. A speed regulation strategy for the cooling fan with short inlet duct is proposed, which provides guidance for the application of this noise reduction method.

Study on Surface Radiation Noise of a Diesel Engine Based on FEM

2013 ◽  
Vol 774-776 ◽  
pp. 17-20 ◽  
Author(s):  
Ye Miao Zhao ◽  
Xiao Hui Cao ◽  
Chen Hai Guo ◽  
Qing Zhen Ma
Keyword(s):  
Diesel Engine ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Combustion Engine ◽  
Element Model ◽  
Noise Spectrum ◽  
Surface Radiation ◽  
Vibration Velocity ◽  
Finite Element Software ◽  
Radiation Noise

To evaluate the noise of a diesel engine and provide the basis for the next step for noise reduction, a boundary element model of the diesel engine has been built and finite element software is used to analyze the noise of the engine. Surface vibration velocity distribution, radiation noise spectrum, sound pressure distribution and total noise level are calculated. The calculation results obtained show that the most representative three points of the peak of SPL (sound pressure level) are 500Hz, 1200Hz and 1950Hz; total SPL is 108.99dB; the main sources of the noise of the diesel engine are oil pan, gear chamber cover and flywheel housing, these three parts should be prior; the noise of the lower part and left and right part (the gear chamber cover side and flywheel housing side) of the engine is greater than the upper part and front and rear part; improving the suspension mechanism of the internal combustion engine, optimizing the oil sump, flywheel housing and gear chamber cover and strengthening the rigidity of the skirt of the engine body can be used as the primary means of noise reduction.

A study for practical application of aerodynamic noise reduction method of pantograph head and its support

2020 ◽  
Vol 2020.30 (0) ◽  
pp. 106
Author(s):  
Takeshi MITSUMOJI ◽  
Takayuki USUDA ◽  
Hiromasa HIRAKAWA ◽  
Tatsushi ISONO ◽  
Kyohei NAGAO ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Reduction Method ◽  
Aerodynamic Noise ◽  
Practical Application

scholarly journals Research on the Mechanism of Fan Blade Shape Effect on its Noise

2005 ◽  
Vol 24 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Linling Li ◽  
Qibai Huang
Keyword(s):  
Sound Pressure ◽  
Model Simulation ◽  
Aerodynamic Characteristics ◽  
Shape Effect ◽  
Blade Design ◽  
Fan Noise ◽  
Factors Affecting ◽  
Blade Shape ◽  
Fan Blade ◽  
Major Factors

The fan blade configuration affects its efficiency and sound pressure level—(SPL). This paper analyzes the fan blade noise components and studies the aerodynamic characteristics of fan blades. The bar theory and moving soundfield characteristics are used in the theoretical analysis. Nonlinear aerodynamics theory is used to analyze the blade force. A mathematical model of fan blade noise is developed and simulated by the precision Gauss-Legendre method. The model simulation and the experiment results are analyzed in the frequency domain. The simulation results are in reasonable agreement with the measured data. Our model and the Fukano model are compared for different rotational speeds of the fan. This paper then studies the change of SPL when the blade parameters (number of blades, rotation speed of fan, chord of fan, and blade profile etc.) vary. The major factors affecting the fan noise are analyzed. Our model is derived from the viewpoint of blade design, so the result can be used to study the aerodynamic characteristics of fan blades quantitatively. The study is considered as a prerequisite to designing fans of high quality, since it provides a theoretical basis for noise prediction and noise control.

Investigation on flow oscillation modes and aero-acoustics generation mechanism in cavity

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840046 ◽  
Author(s):  
Dang-Guo Yang ◽  
Bo Lu ◽  
Jin-Sheng Cai ◽  
Jun-Qiang Wu ◽  
Kun Qu ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Simulation Method ◽  
Aerodynamic Noise ◽  
Sound Waves ◽  
Detached Eddy Simulation ◽  
Flow Oscillation ◽  
Rear Wall ◽  
Supersonic Wind Tunnel ◽  
Acoustic Characteristics ◽  
Oscillation Modes

Unsteady flow and multi-scale vortex transformation inside a cavity of L/D = 6 (ratio of length to depth) at Ma = 0.9 and 1.5 were studied using the numerical simulation method of modified delayed detached eddy simulation (DDES) in this paper. Aero-acoustic characteristics for the cavity at same flow conditions were obtained by the numerical method and 0.6 m by 0.6 m transonic and supersonic wind-tunnel experiments. The analysis on the computational and experimental results indicates that some vortex generates from flow separation in shear-layer over the cavity, and the vortex moves from forward to downward of the cavity at some velocity, and impingement of the vortex and the rear-wall of the cavity occurs. Some sound waves spread abroad to the cavity fore-wall, which induces some new vortex generation, and the vortex sheds, moves and impinges on the cavity rear-wall. New sound waves occur. The research results indicate that sound wave feedback created by the impingement of the shedding-vortices and rear cavity face leads to flow oscillations and noise generation inside the cavity. Analysis on aero-acoustic characteristics inside the cavity is feasible. The simulated self-sustained flow-oscillation modes and peak sound pressure on typical frequencies inside the cavity agree well with Rossiter’s and Heller’s predicated results. Moreover, the peak sound pressure occurs in the first and second flow-oscillation modes and most of sound energy focuses on the low-frequency region. Compared with subsonic speed (Ma = 0.9), aerodynamic noise is more intense at Ma = 1.5, which is induced by compression wave or shock wave in near region of fore and rear cavity face.

Computational Aeroacoustic Simulation of Landing Gear

2013 ◽  
Vol 421 ◽  
pp. 110-115
Author(s):  
Guang Jun Yang ◽  
Jian Jun Liu ◽  
Jing Sun
Keyword(s):  
Noise Analysis ◽  
Near Field ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Noise Spectrum ◽  
Landing Gear ◽  
Aerodynamic Noise ◽  
Acoustic Characteristics ◽  
Initial Flow ◽  
Noise Characteristics

RANS / NLAS numerical simulation method is adopted in this paper to carry out study on the aerodynamic noise analysis of basic landing gear configuration. Reynolds average N-S equation is solved with nonlinear turbulence model to establish the landing gear initial flow field, based on which, the NLAS (nonlinear acoustic solver) processed the turbulence fluctuation reconstruction to obtain the near-field acoustic characteristics of landing gear. Combined with the flow characteristics and the associated noise spectrum analysis, aerodynamic noise characteristics of landing gear are achieved. The work in this paper can provide useful research foundation on the following noise reduction design of landing gear.

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

Study on flow field and aerodynamic noise of electric vehicle rearview mirror

2021 ◽  
pp. 095440702110228
Author(s):  
Xiaowei Hao ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
Electric Vehicle ◽  
Sound Pressure ◽  
Pressure Level ◽  
Orthogonal Decomposition ◽  
Aerodynamic Noise ◽  
Turbulent Pressure ◽  
Rearview Mirror ◽  
Proper Orthogonal

With the development of new energy and intelligent vehicles, aerodynamic noise problem of pure electric vehicles at high speed has become increasingly prominent. The characteristics of the flow field and aerodynamic noise of the rearview mirror region were investigated by large eddy simulation, acoustic perturbation equations and reduction order analysis. By comparing the pressure coefficients of the coarse, medium and dense grids with wind tunnel test results, the pressure distribution, and numerical accuracy of the medium grid on the body are clarified. It is shown from the flow field proper orthogonal decomposition of the mid-section that the sum of the energy of the first three modes accounts for more than 16%. Based on spectral proper orthogonal decomposition, the peak frequencies of the first-order mode are 19 and 97 Hz. As for the turbulent pressure of side window, the first mode accounts for approximately 11.3% of the total energy, and its peak appears at 39 and 117 Hz. While the first mode of sound pressure accounts for about 41.7%, and the energy peaks occur at 410 and 546 Hz. Compared with traditional vehicle, less total turbulent pressure level and total sound pressure level are found at current electric vehicle because of the limited interaction between the rearview mirror and A-pillar.

Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

2021 ◽  
pp. 095441002098822
Author(s):  
Dian Li ◽  
Xiaomin Liu ◽  
Lei Wang ◽  
Fujia Hu ◽  
Guang Xi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Numerical Study ◽  
Barn Owl ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Reduction Mechanisms ◽  
Trailing Edge Serrations ◽  
Bionic Airfoil

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

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