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Research on the Generation Mechanism and Suppression Method of aerodynamic noise in Expansion Cavity Based on Hybrid Method

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 2747-2772页

作者： Haitao Liu Jiaming Wang Xiuliang Zhang Yanji Jiang Qian Xiao School of Mechanotronics and Vehicle Engineering East China Jiaotong UniversityNanchang330013China Suzhou Automotive Research Institue Tsinghua UniversitySuzhou215131China

The expansion chamber serves as the primary silencing structure within the exhaust pipeline.However,it can also act as a sound-emitting structure when subjected to airflow.This article presents a hybrid method for numerically simulating and analyzing the unsteady flow and aerodynamic noise in an expansion chamber under the influence of airflow.A fluid simulation model is established,utilizing the Large Eddy Simulation(LES)method to calculate the unsteady flow within the expansion chamber.The simulation results effectively capture the development and changes of the unsteady flow and vorticity inside the cavity,exhibiting a high level of consistency with experimental observations.To calculate the aerodynamic noise sources within the cavity,the flow field results are integrated using the method of integral interpolation and inserted into the acoustic grid.The acoustic analogy method is then employed to determine the aerodynamic noise sources.An acoustic simulation model is established,and the flow noise source is imported into the sound field grid to calculate the sound pressure at the far-field response point.The calculated sound pressure levels and resonance frequencies show good agreement with the experimental results.To address the issue of airflow regeneration noise within the cavity,perforated tubes are selected as a means of noise suppression.An experimental platformfor airflow regeneration noise is constructed,and experimental samples are processed to analyze and verify the noise suppression effect of perforated tube expansion cavities under different airflow velocities.The research findings indicate that the perforated tube expansion cavity can effectively suppress low-frequency aerodynamic noise within the cavity by impeding the formation of strong shear layers.Moreover,the semi-perforated tube expansion cavity demonstrates the most effective suppression of aerodynamic noise.

关键词： Expansion cavity aerodynamic noise numerical simulation hybrid method perforated tube

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Numerical Study on Reduction in aerodynamic Drag and noise of High-Speed Pantograph

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2155-2173页

作者： Deng Qin Xing Du Tian Li Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China School of Electrical Engineering Southwest Jiaotong UniversityChengdu610031China

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train technology.Using computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed pantographs.The results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed pantographs.Therefore,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and noise.By optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be reduced.The aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the largest.Ellipsifying insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the pantograph.In addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated noise.In contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise.

关键词： High-speed pantograph aerodynamic drag aerodynamic noise reduction optimizing

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Effect of Bogie Cavity End Wall Inclination on Flow Field and aerodynamic noise in the Bogie Region of High-Speed Trains

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2175-2195页

作者： Jiawei Shi Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China

Combining the detached eddy simulation(DES)method and Ffowcs Williams-Hawkings(FW-H)equation,the effect of bogie cavity end wall inclination on the flow field and aerodynamic noise in the bogie region is numerically studied.First,the simulation is conducted based on a simplified cavity-bogie model,including five cases with different inclination angles of the front and rear walls of the cavity.By comparing and analyzing the flow field and acoustic results of the five cases,the influence of the regularity and mechanism of the bogie cavity end wall inclination on the flow field and the aerodynamic noise of the bogie region are revealed.Then,the noise reduction strategy determined by the results of the simplified cavity-bogie model is applied to a three-car marshaling train model to verify its effectiveness when applied to the real train.The results reveal that the forward inclination of the cavity front wall enlarges the influence area of shear vortex structures formed at the leading edge of the cavity and intensifies the interaction between the vortex structures and the front wheelset,frontmotor,and front gearbox,resulting in the increase of the aerodynamic noise generated by the bogie itself.The backward inclination of the cavity rear wall is conducive to guiding the vortex structures flow out of the cavity and weakening the interaction between the shear vortex structures and the cavity rear wall,leading to the reduction of the aerodynamic noise generated by the bogie cavity.Inclining the rear end wall of the foremost bogie cavity of the head car is a feasible aerodynamic noise reduction measure for high-speed trains.

关键词： Bogie cavity flow aerodynamic noise end wall inclination

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Analysis of Influence on aerodynamic noise of Wind Turbine Blades under Different Pitch Angles

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Open Journal of Applied Sciences 2024年第5期14卷 1237-1250页

作者： Ruirong He Houcai Liu Huimin Kang Jiale Xi School of Mechanical and Electrical Engineering Hunan University of Science and Technology Xiangtan China

Aiming at the influence of blade pitch Angle on aerodynamic noise of wind turbines, the sound field and flow field distribution at 0˚, 5˚, 10˚ and 15˚ are calculated by numerical simulation. Then, through the distribution of pressure field and velocity field calculated by flow field, the influence of different pitch angles on wind turbine blade aerodynamic noise and the reasons for its influence are analyzed. The results show that when the pitch Angle increases within 0˚ - 10˚, the aerodynamic noise pressure level of the blade decreases. However, the sound pressure level of aerodynamic noise increases in the range of 10˚ - 15˚. The changes of static pressure gradient and pressure pulsation on the blade surface make the aerodynamic noise change, and the changes of the two are positively correlated. At the same time, the fluid velocity and fluid motion state on the blade surface are closely related to the aerodynamic noise of the blade. The greater the fluid velocity, the more complex the fluid motion state and the greater the turbulent kinetic energy of the wind turbine blade, and the aerodynamic noise of the wind turbine blade will also increase.

关键词： Pitch Angle aerodynamic noise Static Pressure Gradient Fluid Motion Numerical Simulation

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Step-by-Step Numerical Prediction of aerodynamic noise Generated by High Speed Trains

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Chinese Journal of Mechanical Engineering 2022年第2期35卷 251-264页

作者： Tian Li Deng Qin Ning Zhou Weihua Zhang State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

In this paper,the unsteady flow around a high-speed train is numerically simulated by detached eddy simulation method(DES),and the far-field noise is predicted using the Ffowcs Williams-Hawkings(FW-H)acoustic model.The reliability of the numerical calculation is verified by wind tunnel experiments.The superposition relationship between the far-field radiated noise of the local aerodynamic noise sources of the high-speed train and the whole noise source is analyzed.Since the aerodynamic noise of high-speed trains is derived from its different components,a stepwise calculation method is proposed to predict the aerodynamic noise of high-speed trains.The results show that the local noise sources of high-speed trains and the whole noise source conform to the principle of sound source energy superposition.Using the head,middle and tail cars of the high-speed train as noise sources,different numerical models are established to obtain the far-field radiated noise of each aerodynamic noise source.The far-field total noise of high-speed trains is predicted using sound source superposition.A step-by-step calculation of each local aerodynamic noise source is used to obtain the superimposed value of the far-field noise.This is consistent with the far-field noise of the whole train model’s aerodynamic noise.The averaged sound pressure level of the far-field longitudinal noise measurement points differs by 1.92 dBA.The step-by-step numerical prediction method of aerodynamic noise of high-speed trains can provide a reference for the numerical prediction of aerodynamic noise generated by long marshalling high-speed trains.

关键词： High-speed train aerodynamic noise Sound source superposition Numerical prediction

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A novel hybrid method for aerodynamic noise prediction of high-lift devices

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中国航空学报:英文版 2023年第9期36卷 151-161页

作者： Jun TAO Gang SUN Department of Aeronautics&Astronautics Fudan UniversityShanghai 200433China Key Laboratory of aerodynamic noise Control China Aerodynamics Research and Development CenterMianyang 621000China

aerodynamic noise of High-Lift Devices(HLDs)is one of the main sources of airframe noise,and has immediate impacts on the airworthiness certification,environmental protection and security of commercial aircraft.In this study,a novel hybrid method is proposed for the aerodynamic noise prediction of HLD.A negative Spalart-Allmaras(S-A)turbulence model based Improved Delayed Detached Eddy Simulation(IDDES)method coupling with AFT-2017b transition model is developed,in order to elaborately simulate the complex flow field around the HLD and thus obtain the information of acoustic sources.A Farassat-Kirchhoff hybrid method is developed to filter the spurious noise sources caused by the vortex motions in solving the Ffowcs Williams-Hawkings(FW-H)equation with permeable integral surfaces,and accurately predict the far-field noise radiation of the HLD.The results of the 30P30N HLD indicate that,the computational Sound Pressure Levels(SPLs)obtained by the Farassat-Kirchhoff hybrid method conform well with the experimental ones in the spectrum for the given observation point,and are more accurate than those obtained by the Farassat 1A method.Based on the hybrid method,the acoustic directivity of the HLD of a commercial aircraft is obtained,and the variation of the SPLs in the spectrum with the deflection angle of the slat is analyzed.

关键词： aerodynamic noise Farassat-Kirchhoff hybrid method High-lift devices IDDES Negative S-A turbulence model

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A Numerical Investigation on the Influence of the Circular Ring on the aerodynamic noise Generated by a Cooling Fan

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Fluid Dynamics & Materials Processing 2023年第1期19卷 1-14页

作者： Jun Feng Tao Bian Qianpeng Han Bing Wang State Key Laboratory of Precision Blasting Jianghan UniversityWuhan430056China School of Intelligent Manufacturing Jianghan UniversityWuhan430056China Key Laboratory of Optoelectronic Chemical Materials and Devices Ministry of EducationSchool of Chemical and Environmental EngineeringJianghan UniversityWuhan430056China Institute for Interdisciplinary Research Jianghan UniversityWuhan430056China Guangdong HUST Industrial Technology Research Institute Dongguan523429China

The influence of the width of the circular ring of a car cooling fan on the aerodynamic noise is investigated numerically through the determination of the overall sound pressure level(OASPL).The results demonstrate that when the circular rings cover near 2/3 of the width of the blade tips of the rotor in the axis direction,the rotor has the lowest OASPL and the related total pressure efficiency and flow mass rate are better than the corresponding values obtained for a reference rotor without a circular ring.With increasing the width of the circular ring in the axis direction,the tip vortex around the trailing edge of the blade tip becomes smaller and finally disappears.Meanwhile,a separated flow field arises gradually and then grows in size around the middle of the junction of the blade tips with the ring.When the circular rings cover nearly 2/3 s of the width of the blade tips of the fan in the axis direction,the extension of the separated flow around the blade’s tip attains a minimum.

关键词： Cooling fan width of the circular ring aerodynamic noise CFD simulation

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Numerical Investigation on the aerodynamic noise Generated by a Simplified Double-Strip Pantograph

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Fluid Dynamics & Materials Processing 2022年第2期18卷 463-480页

作者： Jiawei Shi Shuai Ge Xiaozhen Sheng State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu610031China School of Urban Railway Transportation Shanghai University of Engineering ScienceShanghai201620China

In order to understand the mechanism by which a pantograph can generate aerodynamic noise and grasp its farfield characteristics,a simplified double-strip pantograph is analyzed numerically.Firstly,the unsteady flow field around the pantograph is simulated in the frame of a large eddy simulation(LES)technique.Then the location of the main noise source is determined using surface fluctuating pressure data and the vortex structures in the pantograph flow field are analyzed by means of the Q-criterion.Based on this,the relationship between the wake vortex and the intensity of the aerodynamic sound source on the pantograph surface is discussed.Finally,the far-field aerodynamic noise is calculated by means of the Ffowcs Williams-Hawkings(FW-H)equation,and the contribution of each component to total noise and the frequency spectrum characteristics are analyzed.The results show that on the pantograph surface where vortex shedding or interaction with the wake of upstream components occurs,the pressure fluctuation is more intense,resulting in strong dipole sources.The far-field aerodynamic noise energy of the pantograph is mainly concentrated in the frequency band below 1500 Hz.The peaks in the frequency spectrum are mainly generated by the base frame,balance arm and the rear strip,which are also the main contributors to the aerodynamic noise.

关键词： Pantograph aerodynamic noise vortex structures noise source FW-H equation

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Influence of the Blade Bifurcated Tip on the Correlation between Wind Turbine Wheel Vibration and aerodynamic noise

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Fluid Dynamics & Materials Processing 2023年第12期19卷 3033-3043页

作者： Baohua Li Yuanjun Dai Jingan Cui Cong Wang Kunju Shi Mechanical College Shanghai Dianji UniversityShanghai201306China College of Energy Engineering Xinjiang Institute of EngineeringUrumqi830091China

To reduce the vibration and aerodynamic noise of wind turbines,a new design is proposed relying on a blade with a bifurcated apex or tip.The performances of this wind turbine wheel are tested at the entrance of a DC(direct-action)wind tunnel for different blade tip angles and varying centrifugal force and aerodynamic loads.The test results indicate that the bifurcated apex can reduce the vibration acceleration amplitude and the vibration fre-quency of the wind wheel.At the same time,the bifurcated apex can lower the maximum sound pressure level corresponding to the rotating fundamental frequency of the wind wheel.According to all thesefindings,the tip angle of the bifurcated apex is the main factor enhancing the effect of the modification.

关键词： Wind turbine bifurcated apex wind wheel vibration aerodynamic noise

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Study on the flow behaviour and aerodynamic noise characteristics of a high-speed pantograph under crosswinds

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Science China(Technological Sciences) 2020年第6期63卷 977-991页

作者： ZHANG YaDong ZHANG JiYe SHENG XiaoZhen Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055China State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

The aerodynamic noise of high-speed trains increases significantly under crosswinds.Researches have typically focused on the characteristics of aerodynamic loads and the corresponding safety issues,with less attention to flow-induced noise characteristics.In the present paper,the near-field unsteady flow behaviour around a pantograph was analysed using a large eddy simulation.The far-field aerodynamic noise from a pantograph was predicted using the Ffowcs Williams-Hawkings acoustic analogy.The results showed that asymmetric characteristics of the flow field could be observed using the turbulent kinetic energy and the instantaneous vortexes in crosswind conditions.Vortex shedding,flow separation and recombination around the pantograph were the key factors for aerodynamic noise generation.The directivity of the noise radiation was inclined towards the leeward side of the pantograph.The aerodynamic noise propagation pattern can be considered as a typical point source on spherical waves when the transverse distance from the pantograph geometrical centre is farther than 8 m.The sound pressure level grew approximately as the 6 th power of the pantograph speed.The peak frequency exhibited a linear relationship with the crosswind velocity.The numerical simulation results and wind tunnel experiments had high consistency in the full frequency domain,namely,the peak frequency distribution range,the main frequency amplitude and the spectral distribution shape.

关键词： pantograph high-speed trains crosswind aerodynamic noise flow behaviour FW-H integral equation

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