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An uncertainty investigation for liner impedance eduction methods

Chinese Journal of Aeronautics 2024年第3期37卷 49-59页

作者： Weihao SHI xiaodong jing School of Energy and Power Engineering Beihang UniversityBeijing 100191China

Impedance eduction methods have been developed for decades to meet the increasing need for high-quality impedance data in the design and optimization of acoustic *** this end,it is important to fully investigate the uncertainty problem,to which only limited attention has been devoted so *** paper considers the possibility of acoustically-induced structural vibration as a nonnegligible uncertainty or error source in impedance eduction *** the frequency moves away from the resonant frequency,with the increase in the value of cavity reactance,the acoustic particle velocity inside liner orifices possibly decreases to the extent comparable to the vibration velocity of liner facing ***,the acoustically-induced vibration,although generally being weak except at the inherent structural frequencies,may considerably affect the impedance eduction results near the anti-resonant frequency where the liner has poor *** demonstrate the effect of structural vibration,the vibration velocity of liner facing sheet is estimated from the experimentally educed admittance of the liner samples whose orifices are sealed with ***,a three-dimensional numerical model is set up,in which normal particle velocity is introduced over the solid portion of liner facing sheet to imitate structural vibration,rather than directly solving the acoustic-structural coupling *** shown by the results,the vibration of liner facing sheet,whose velocity is as small as estimated by the experiment,can result in anomalous deviation of the educed impedance from the impedance model near the anti-resonant *** trend that the anomalous deviation varies with frequency is numerically captured.

关键词： Impedance eduction Uncertainty analysis Acoustically-induced structural vibration Anti-resonant frequency Perforated liner

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Temperature field simulation of polyolefin-absorber mixture by FDTD-FDM model during microwave heating

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Chinese Journal of Chemical Engineering 2020年第11期28卷 2900-2917页

作者： xiaodong jing Hao Wen Zhihong Xu State Key Laboratory of Multiphase Complex Systems Beijing Engineering Research Centre of Process Pollution ControlInstitute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

This work has performed a numerical simulation of the temperature field during microwave heating of polyolefin-absorber mixture by means of a combined electric and thermal model.A finite difference time domain was used to model the electric field distribution within the cavity,while the finite difference method was used to calculate the temperature field distribution in different *** study has focused only on the process from room temperature to 500 K for reducing heating time and energy *** temperature range is a process with high energy consumption,difficult to control and great influence on the follow-up *** dependence of dielectric properties and thermal properties of heated materials are fully considered and simulated through an iterative *** simulation results show that input power,the size and location of the heated materials,the position of the waveguide,and the kinds of microwave absorbers are important factors affecting the heating *** a result,the uniform temperature distribution(the temperature difference Tdb10 K)can be achieved by choosing the appropriate input power(500–2000 W),the appropriate proportion of microwave absorber(the volume ratio of Si C to HDPE is 30:70),and combining with the moving and rotating of the heated *** uniform temperature field obtained without mechanical stirring is very important for reducing energy consumption and subsequent reactions.

关键词： Microwave heating Temperature field Finite difference time domain Finite difference method

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Multi-domain Spectral Immersed Interface Method for Solving Elliptic Equation with a Global Description of Discontinuous Functions

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Chinese Journal of Aeronautics 2012年第3期25卷 297-310页

作者： JIANG Yongsong LIANG An SUN Xiaofeng jing xiaodong School of Jet Propulsion Beihang University Beijing 100191 China Department of Compressor Design Shenyang Aeroengine Research Institute Shenyang 110015 China AVIC Commercial Aircrafl Engine Co. Ltd. Shanghai 200241 China

This paper presents the extension of the global description approach of a discontinuous function, which is proposed in the previous paper, to a spectral domain decomposition method. This multi-domain spectral immersed interlace method（IIM） divides the whole computation domain into the smooth and discontinuous parts. Fewer points on the smooth domains are used via taking advantage of the high accuracy property of the spectral method, but more points on the discontinuous domains are employed to enhance the resolution of the calculation. Two that the domain decomposition technique can placed around the discontinuity. The present reached, in spite of the enlarged computational discontinuous problems are tested to verify the present method. The results show reduce the error of the spectral IIM, especially when more collocation points are method is t：avorable for the reason that the same level of the accuracy can be domain.

关键词： computational aerodynamics immersed interface method immersed boundary method Chebyshev spectral method domain decomposition method

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Leach： an automatic learning cache for inline primary deduplication system

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Frontiers of Computer Science 2014年第2期8卷 175-183页

作者： Bin LIN Shanshan LI Xiangke LIAO jing ZHANG xiaodong LIU School of Computer National University of Defense Technology Changsha 410073 China

Deduplication technology has been increasingly used to reduce storage costs. Though it has been successfully applied to backup and archival systems, existing techniques can hardly be deployed in primary storage systems due to the associated latency cost of detecting duplicated data, where every unit has to be checked against a substantially large fin- gerprint index before it is written. In this paper we introduce Leach, for inline primary storage, a self-learning in-memory fingerprints cache to reduce the writing cost in deduplica- tion system. Leach is motivated by the characteristics of real- world I/O workloads： highly data skew exist in the access patterns of duplicated data. Leach adopts a splay tree to or- ganize the on-disk fingerprint index, automatically learns the access patterns and maintains hot working sets in cache mem- ory, with a goal to service a majority of duplicated data de- tection. Leveraging the working set property, Leach provides optimization to reduce the cost of splay operations on the fin- gerprint index and cache updates. In comprehensive experi- ments on several real-world datasets, Leach outperforms con- ventional LRU （least recently used） cache policy by reducing the number of cache misses, and significantly improves write performance without great impact to cache hits.

关键词： deduplication duplicate detection splay tree,cache

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A second-order numerical method for elliptic equations with singular sources using local flter

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Chinese Journal of Aeronautics 2013年第6期26卷 1398-1408页

作者： Jiang Yongsong Fang Le jing xiaodong Sun Xiaofeng Francis Leboeuf Department of Compressor Design AVIC Shenyang Engine Design and Research Institute School of Energy and Power Engineering Beihang University Ecole Centrale de Pe'kin Laboratoire International Associe'Beihang University MOE Key Laboratory of High-speed Railway Engineering Southwest Jiaotong University Ecole Centrale de Lyon Laboratoire de Me'canique des Fluides et d’Acoustique Universite' de LyonEcully 69134France

The presence of Dirac delta function in differential equation can lead to a discontinuity,which may degrade the accuracy of related numerical *** improve the accuracy,a secondorder numerical method for elliptic equations with singular sources is introduced by employing a local kernel *** this method,the discontinuous equation is convoluted with the kernel function to obtain a more regular *** the original equation is replaced by this fltered equation around the singular points,to obtain discrete numerical *** unchanged equations at the other points are discretized by using a central difference scheme.1D and 2D examples are carried out to validate the correctness and accuracy of the present *** results show that a second-order of accuracy can be obtained in the fltering framework with an appropriate integration ***,the present method does not need any jump condition,and also has extremely simple form that can be easily extended to high dimensional cases and complex geometry.

关键词： Computational aerodynamics Immersed boundary method Immersed interface method Kernel flter Singular source

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Investigation of straightforward impedance eduction method on single-degree-of-freedom acoustic liners

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Chinese Journal of Aeronautics 2018年第12期31卷 2221-2233页

作者： Xianghai QIU Bo XIN Long WU Yang MENG xiaodong jing Fluid and Acoustic Engineering Laboratory School of Energy and Power Engineering Beihang University

In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method(SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels(SPLs) and over a frequency range from 3000 Hz down to 500 Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach,predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140 d B in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present,and the grazing flow effect can be reduced partly as well at a relatively high SPL.

关键词： Acoustic liner Experimental validation Grazing flow effect High sound intensity effect Impedance eduction Numerical evaluation Straightforward impedance eduction method

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Experimental study of rotor blades vibration and noise in multistage high pressure compressor and their relevance

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Chinese Journal of Aeronautics 2020年第3期33卷 870-878页

作者： Fengtong ZHAO xiaodong jing Mingsui YANG Deyou WANG Yundong SHA Xiaochi LUAN School of Energy and Power Engineering Beihang UniversityBeijing 100191China Liaoning Province Key Laboratory of Advanced Measurement And Test Technology of Aviation Propulsion Systems Shenyang Aerospace UniversityShenyang 110136China Shenyang Engine Design and Research Institute Aero Engine(Group)Corporation of ChinaShenyang 110015China

Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic *** the excitation factor of high intensity sound wave to rotor blades should not be *** researches are conducted on a multistage high pressure *** high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the *** amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same *** frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating *** high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the *** can be confirmed that acoustic resonance occurs in the multistage *** acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.

关键词： Acoustic resonance Blades vibration Characteristic frequency Multistage compressor Source identification

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Physical model for acoustic resonance in annular cavity structure

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Chinese Journal of Aeronautics 2020年第12期33卷 3228-3237页

作者： Fengtong ZHAO Mingsui YANG xiaodong jing Deyou WANG Yundong SHA Yujin LIU School of Energy and Power Engineering Beihang UniversityBeijing 100083China Liaoning Province Key Laboratory of Advanced Measurement and Test Technology of Aviation Propulsion Systems Shenyang Aerospace UniversityShenyang 110136China Shenyang Engine Research Institute of AECC Shenyang 110015China

A physical model for acoustic resonance in the annular cavity structure is developed to represent the typical characteristic when acoustic resonance ***,the measurement of sound pressure in the casing and rotor blades vibration is operated in a multistage high pressure *** sharp peak frequency and discrete multi-tone occur in the frequency spectrum of sound pressure in the compressor,and the vibration of the first stage of rotor blades synchronously presents the high *** frequencies associated with rotor blades vibration can be calculated with rotating sound source *** is also confirmed that acoustic resonance occurs in the multistage *** acoustic similarity principle,an annular cavity model is established to simulate the typical characteristics of acoustic resonance in the compressor based on Large Eddy Simulation(LES)and Lighthill acoustic *** coupling relationship between cavity acoustic mode and disc vibration mode shape is expounded when acoustic resonance occurs in the *** acoustic resonance will be locked in the certain flow rate *** these characteristics match well with those occur in the multistage high pressure compressor.

关键词： Acoustic resonance Annular cavity structure Large eddy simulation Lighthill acoustic analogy Multistage compressor

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Experimental Study on the Distribution of Velocity and Pressure near a Submarine Pipeline

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Journal of Ocean University of China 2009年第4期8卷 404-408页

作者： HAN Yan SHI Bing REN Xingyue jing xiaodong Engineering College Ocean University of China Qingdao 266 100 P. R. China

As a transport means of oil and gas the submarine pipeline has many merits, such as continuous delivery, large conveying capacity, convenient management, etc. A tube was chosen in our study to simulate the submarine pipeline in the experiments. A high accuracy instrument ADV and high precision point-type pressure sensors were used to measure the parameters of the flow field, including the pressure distribution, velocities at seven cross sections near the submarine pipeline with five different clearance ratios, and twelve dynamic pressure values around the pipeline. The pressure distributions and velocity changes around the pipe under dif- ferent flow velocities and clearance ratios were analyzed. These results might be useful for further study of submarine pipeline ero- sion and protection.

关键词： submarine pipeline velocity field pressure distribution experiment

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ITERATIVE RECEIVER FOR OFDM SYSTEMS BASED ON SEMI-BLIND CHANNEL ESTIMATION

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Journal of Electronics(China) 2007年第2期24卷 163-166页

作者： jing Ya Xu xiaodong Chen Ming Cheng Shixin National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China

In this paper we propose two iterative algorithms of joint channel estimation and symbol detection for Orthogonal Frequency Division Multiplexing (OFDM) systems. In which, superimposed pilot scheme is adopted and an initial Channel State Information (CSI) is obtained by employing a first-order statistic. In each subsequent iteration, we propose two algorithms to update the CSI. The Mean Square Error (MSE) of channel estimation and Bit Error Rate (BER) performance are given and simulation results demonstrate that the iterative algorithm using method B has good perform-ance approaching the ideal condition.

关键词： Orthogonal Frequency Division Multiplexing (OFDM) Iterative receiver Channel estimation Maximum A Posteriori (MAP) probability decoder

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