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Feedback control of boundary layer Tollmien-Schlichting waves using a simple model-based controller

Chinese Journal of Aeronautics 2021年第3期34卷 25-38页

作者： Yong LI zhengwu chen School of Mechanical and Electrical Engineering Wenzhou UniversityWenzhou 325035China Key Laboratory of Aerodynamic Noise Control China Aerodynamic Research and Development CenterMianyang 621000China

The attenuation of spatially evolving instability Tollmien-Schlichting(T-S)waves in the boundary layer of a flat plate with zero pressure gradients using an active feedback control scheme is theoretically and numerically *** boundary layer is excited artificially by various perturbations to create a three-dimensional field of instability *** of actuators and sensors are distributed locally at the wall surface and connected together via a feedback *** key elements of this feedback control are the determination of the dynamic model of the flat plate boundary layer between the actuators and the sensors,and the design of the model-based feedback *** dynamic model is established based on the linear stability calculation which simulates the three-dimensional input-output behaviour of the boundary *** simplify the control problem,an uncoupled control mode of the dynamic model is made to capture only those dynamics that have greatest influences on the input-output behaviour.A Proportional-Integral-Derivative(PID)controller,i.e.a lead-lag compensator,combining with a standard Smith predictor is designed based on the system stability criterion and the specifications using frequency-response *** performance of the feedback control with the uncoupled control mode is demonstrated by the large reduction of the three-dimensional disturbances in the boundary *** simple feedback control is realistic and competitive in a practical implementation of T-S wave cancellation using a limited number of localised sensors and actuators.

关键词： Boundary layer instability Control system Feedback control PID controller Tollmien-Schlichting waves

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High-Order Discontinuous Galerkin Method for Hovering Rotor Simulations Based on a Rotating Reference Frame

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第1期36卷 57-70页

作者： ZHANG Tao Lü Hongqiang QIN Wanglong chen zhengwu Department of Aerodynamics Nanjing University of Aeronautics and Astronautics China Aerodynamics Research and Development Center

An implicit higher ? order discontinuous Galerkin(DG) spatial discretization for the compressible Euler equations in a rotating frame of reference is presented and applied to a rotor in hover using hexahedral grids. Instead of auxiliary methods like grid adaptation,higher ? order simulations(fourth ? and fifth ? order accuracy) are *** numerical experiments are carefully designed,conducted and analyzed. The results show generally excellent consistence with references and vigorously demonstrate the higher?order DG method's better performance in loading distribution computations and tip vortex capturing, with much fewer degrees of freedom(DoF). Detailed investigations on the outer boundary conditions for hovering rotors are presented as well. A simple but effective speed smooth procedure is developed specially for the DG method. Further results reveal that the rarely used pressure restriction for outlet speed has a considerable advantage over the extensively adopted vertical speed restriction.

关键词： high-order method(HOM) discontinuous Glaerkin method(DGM) Euler equation hovering rotor simulation tip vortex

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Implicit discontinuous Galerkin method on agglomerated high-order grids for 3D simulations

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Chinese Journal of Aeronautics 2016年第6期29卷 1496-1505页

作者： Qin Wanglong Lyu Hongqiang Wu Yizhao Zhou Shijie chen zhengwu Department of Aerodynamics Nanjing University of Aeronautics and AstronauticsNanjing 210016China China Aerodynamics Research and Development Center Mianyang 621000China

High quality of geometry representation is regarded essential for high-order methods to maintain their high-order accuracy. An agglomerated high-order mesh generating method is investigated in combination with discontinuous Galerkin(DG) method for solving the 3D compressible Euler and Navier-Stokes equations. In this method, a fine linear mesh is first generated by standard commercial mesh generation tools. By taking advantage of an agglomeration method, a quadratic high-order mesh is quickly obtained, which is coarse but provides a high-quality geometry representation, thus very suitable for high-order computations. High-order discretizations are performed on the obtained grids with DG method and the discretized system is treated fully implicitly to obtain steady state solutions. Numerical experiments on several flow problems indicate that the agglomerated high-order mesh works well with DG method in dealing with flow problems of curved geometries. It is also found that with a fully implicit discretized system and a p-sequencing method, the DG method can achieve convergence state within several time steps which shows significant efficiency improvements compared to its explicit counterparts.

关键词： Agglomeration Discontinuous Galerkin(DG) High-order Implicit scheme Navier-Stokes equations

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Transcriptome and co-expression network analysis uncover the key genes mediated by endogenous defense hormones in tea plant in response to the infestation of Empoasca onukii Matsuda

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Beverage Plant Research 2023年第1期3卷 29-41页

作者： Dahe Qiao Chun Yang Yan Guo Juan chen zhengwu chen Tea Research Institute Guizhou Academy of Agricultural SciencesGuiyang 550006GuizhouChina

The tea green leafhopper[Empoasca(Matsumurasca)onukii Matsuda]is one of the most dominant pests in the tea production regions of China,greatly impacting tea yield and *** studies have attributed the plant defense response to pest infestation to the activation of hormone signals,but the role of defense hormones in tea plants in response to the feeding of *** is not ***-seq was performed on the leaf samples collected at different time points(6,24 and 48 h)after feeding with *** to explore the transcription characteristics of tea plant responses to *** content variation characteristics of four phytohormones(JA,JA-Ile,ABA and SA)during this process were also *** results showed that feeding elevated the expression of key genes involved in phenylpropanoid biosynthesis,flavonoid biosynthesis,α-linolenic acid metabolism and terpenoids synthesis pathways,especially in the early stage after *** contents of JA,JA-Ile,and ABA dramatically increased at different time points after feeding,but the absolute content decreased over *** change in the absolute content of SA was opposite to that of the above three *** gene co-expression networks that were significantly positively associated with these hormonal changes were constructed based on *** screened hub genes provide useful genetic resources for exploring the hormone-mediated defense responses of tea plants against *** results lay the foundation for the ecological control of *** and breeding of resistant tea plant cultivars.

关键词： absolute attributed opposite

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Investigation of the fast magnetosonic wave excited by the Alfvén wave phase mixing by using the Hall–MHD model in inhomogeneous plasma

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Plasma Science and Technology 2021年第3期23卷 22-29页

作者： Zhongzheng LI Juanfang HAN Fangping WANG zhengwu chen Wenshan DUAN College of Physics and Electronic Engineering Northwest Normal UniversityLanzhou 730070People's Republic of China Department of Physics Gansu Normal College For NationalitiesHezuo 747000People's Republic of China

The inhomogeneity is introduced by a nonzero density gradient which separates the plasma into two different regions where plasma density are *** Alfvén waves,the phase mixing and the fast magnetosonic wave are excited by the boundary condition in inhomogeneous magnetized *** using the Hall–magnetohydrodynamics(MHD)model,it is found that there are Alfvén waves in the homogeneous regions,while the phase mixing appears in the inhomogeneous *** interesting result is that a fast magnetosonic wave is excited in a different direction which has a nonzero angle between the wave propagation direction and the direction of the background magnetic *** dependence of the propagation direction of the excited fast magnetosonic wave and its strength of the magnetic field on the plasma parameters are given *** results show that increasing both the driving frequency and the ratio of magnetic pressure to thermal pressure will increase the acceleration of the *** electron acceleration also depends on the inhomogeneity parameters.

关键词： Hall–MHD Alfvén wave phase mixing numerical simulations fast magnetosonic wave

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Experimental investigation of self-oscillation feedback flow field structure and flow induced aeroacoustics for an open cavity in low speed wind tunnel

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Chinese Journal of Acoustics 2022年第4期41卷 358-372页

作者： LIANG Yong chen Yingchun ZHAO Kun WANG Yong YUE Tingrui chen zhengwu Low Speed Institute China Aerodynamics Research and Development CenterMianyang 621000 School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072 Commercial Aircraft Corporation of China Ltd.Shanghai 201200

To investigate the noise issue caused by open-cavity self-sustained oscillations,flow over a rectangular cavity with a length-to-depth ratio of 2 at Mach numbers of 0.10,0.15,0.20,and 0.25 was experimentally studied in a 0.55 m×0.40 m aeroacoustics wind ***,the velocity field and self-sustained oscillation were ***-frequency particle image velocimetry was employed to visualise the flow-field structure and analyse the path of the acoustic and pressure *** acoustic self-sustaining oscillation modes and duct modes were investigated by testing the far field and the fluctuating wall ***,the characteristics of the correlation between the wall pressure and the acoustic performance were *** results demonstrated that apart from the main vortex structure,shear vortices at the leading edge and crash vortices at the trailing edge were ***,around the frequencies of 875 Hz,1288 Hz,1875 Hz,and 2050 Hz,an evident tonal noise,induced by the cavity oscillation,could be *** addition,the wall pressure strongly correlated with the far-field noise,and the tone appeared at the same frequencies where the peaks occurred in the wall pressure spectra.

关键词： oscillation flow field

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Non-thermal plasma fixing of nitrogen into nitrate： solution for renewable electricity storage？

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Frontiers of Optoelectronics 2018年第1期11卷 92-96页

作者： Yi HE zhengwu chen Zha LI Guangda NIU Jiang TANG Wuhan National Laboratory for Optoelectronics (WNLO) Huazhong University of Science and Technology Wuhan 430074 China

The rapid deployment of solar and wind technology produces significant amount of low-quality electricity that calls for a better storage or usage instead of being discarded by the *** of electrochemical CO2 reduction and/or NH3 production,here we propose that non-thermal plasma oxidation of N2 into nitrate or other valuable nitrogen containing compounds deserve more research attention because it uses free air as the reactant and avoids the solubility difficulty,and also because its energy consumption is merely 0.2 MJ/mol,even lower than the industrially very successful Haber-Bosch process（0.48 MJ/mol）for NH3 *** advocate that researchers from the plasma community and chemistry community should work together to build energy efficient non-thermal plasma setup,identify robust,active and low-cost catalyst,and understand the catalyzing mechanism in a plasma *** are confident that free production of nitrate with zero C02 emission will come true in the near future.

关键词： energy storage nitrogen fixation non-thermal plasma

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Pressure field measurements on large-scale propeller blades using pressure-sensitive paint

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Acta Mechanica Sinica 2022年第2期38卷 35-45,I0001页

作者： Chunhua Wei Lingrui Jiao Fan Tong zhengwu chen Yingzheng Liu Di Peng China Aerodynamic Research and Development Center Mianyang 621000China Key Lab of Education Ministry for Power Machinery and Engineering School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Gas Turbine Research Institute Shanghai Jiao Tong UniversityShanghai 200240China

Pressure-sensitive paint(PSP)is a global pressure measurement *** with pressure transducers,PSP has significant advantages such as high spatial resolution and a lack of contact when applied to fast-rotating ***,due to the limitations of other pressure measurement techniques,the validation of PSP measurements on fast-rotating blades is generally *** this work,a comprehensive study including PSP measurement,force balance measurement,and simulation was conducted on a 1 m-diameter propeller at the China Aerodynamic Research and Development ***,our computational fluid dynamics(CFD)code was validated by comparing the calculated aerodynamic thrust with the results from force balance ***,the pressure distributions on the propeller blade obtained by PSP were carefully compared with the CFD results under different working *** results of PSP measurements,force balance measurements,and CFD showed good agreement,and the PSP measurement errors were estimated to be less than 5% of the dynamic pressure at the blade ***,the variations in pressure distribution under different rotating speeds and free-stream velocities were discussed.

关键词： Pressure-sensitive paint Pressure distribution Propeller blade

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部分空间和部分时间相干衍射高斯-谢尔模型脉冲光束在大气湍流中的光谱移动和光谱开关

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红外与激光工程 2011年第5期40卷 864-871页

作者：陈正武付文羽甘肃民族师范学院物理与水电工程系甘肃合作747000 陇东学院物理与电子工程学院甘肃庆阳745000

基于非稳光场的相干光理论,研究了部分空间和部分时间相干高斯-谢尔模型脉冲光束在大气湍流中的光谱变化规律。给出了两者在大气湍流中的光谱传输公式。数值计算结果表明,由于光阑衍射效应的影响,光谱沿轴向、径向均出现蓝移或红移,随... 详细信息

基于非稳光场的相干光理论,研究了部分空间和部分时间相干高斯-谢尔模型脉冲光束在大气湍流中的光谱变化规律。给出了两者在大气湍流中的光谱传输公式。数值计算结果表明,由于光阑衍射效应的影响,光谱沿轴向、径向均出现蓝移或红移,随着相对传输距离z/z0、空间相干参数β和折射率结构常数C2n的增大,脉冲时间相干长度Tc的减小,轴向光谱蓝移量(或红移量)逐渐增大,由明显的起伏逐渐趋于稳定并且沿径向出现了光谱开关。其数目随着截断参数δ的增大,光阑的衍射效应减弱而逐渐增多,光谱跃迁量△逐渐减小;随着脉冲时间相干长度的增大,光谱跃迁量逐渐减小,开关位置逐渐靠近z轴;而随着折射率结构常数的增大,光谱跃迁量逐渐减小,开关位置逐渐远离z轴。随着相对传输距离的增大,大气湍流对光谱的影响逐渐增大而光阑衍射效应逐渐减小,因此,光阑衍射在近场区对光谱影响较大,而大气湍流在远场区对光谱影响较大。

关键词：大气光学部分空间和部分时间相干脉冲高斯-谢尔模型光束光谱移动和光谱开关湍流大气

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传声器阵列特征值滤波去噪方法

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声学学报 2021年第3期46卷 335-343页

作者：余亮潘铮陈正武蒋伟康上海交通大学机械系统与振动国家重点实验室上海200240 哈工智能中央研究院上海201100 中国空气动力研究与发展中心气动噪声控制重点实验室绵阳621000

作为二阶统计量的互谱矩阵(CSM)是声学成像算法的核心输入量。为增强传声器阵列的去噪表现,研究了互谱矩阵特征值滤波的机理,并提出了两种新型的特征值滤波方法的设计准则:(1)声源互谱矩阵的Stein无偏风险估计(SURE收缩),即基于SURE准... 详细信息

作为二阶统计量的互谱矩阵(CSM)是声学成像算法的核心输入量。为增强传声器阵列的去噪表现,研究了互谱矩阵特征值滤波的机理,并提出了两种新型的特征值滤波方法的设计准则:(1)声源互谱矩阵的Stein无偏风险估计(SURE收缩),即基于SURE准则的特征值软阈值收缩;(2)进一步提高声源互谱矩阵EYM(Eckart-Young-Mirsky)估计误差的最优收缩(Opt-Shrinkage)方法,即对声源特征值所含有的噪声进一步去除。然后,在3000个快照数,0 dB信噪比(SNR),100个传声器的环境下进行仿真。通过仿真,与经典的MUSIC方法比较原声源信号与去噪后信号的互谱矩阵对角线误差,其中MUSIC方法的互谱矩阵对角线误差为74.15%,SURE收缩为41.97%,最优收缩为20.62%。并通过改变快照数、声源数与SNR,对比了不同特征值滤波去噪方法的效果。从仿真结果上看,在少声源(少于40个)工况下SURE收缩方法的去噪效果优于MUSIC方法与最优收缩方法;在声源数超过42个后,最优收缩方法取得更显著的效果。最后,在3个声源、60个传声器数、-5 dB信噪比的声源定位实验中,SURE收缩与最优收缩均获得了相比MUSIC方法更好的去噪效果。研究表明在现有传声器阵列特征值滤波方法的基础上,对特征值的进一步处理可以得到更好的去噪效果。

关键词：声源定位传声器阵列特征值

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