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Numerical study of the near-wall vortical structures in particle-laden turbulent flow by a new vortex identification method-liutex

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Journal of Hydrodynamics 2024年第1期36卷 53-60页

作者： Farid Rousta Goodarz Ahmadi Bamdad Lessani chaoqun liu Department of Mechanical and Aerospace Engineering Clarkson UniversityPotsdamNYUSA Mechanical Engineering and Engineering Science The University of North Carolina at CharlotteNCUSA Department of Mathematics University of Texas at ArlingtonArlingtonTXUSA

This study investigates turbulent particle-laden channel flows using direct numerical simulations employing the Eulerian-Lagrangian method.A two-way coupling approach is adopted to explore the mutual interaction between particles and fluid *** considered cases include flow with particle Stokes number varying from St=2 up to St=100 while maintaining a constant Reynolds number of Reτ=180 across all cases.A novel vortex identification method,liutex(Rortex),is employed to assess its efficacy in capturing near-wall turbulent coherent structures and their interactions with *** liutex method provides valuable information on vortex strength and vectors at each location,enabling a detailed examination of the complex interaction between fluid and particulate *** widely acknowledged,the interplay between clockwise and counterclockwise vortices in the near-wall region gives rise to low-speed streaks along the *** low-speed streaks serve as preferential zones for particle concentration,depending upon the particle Stokes *** is shown that the liutex method can capture these vortices and identify the location of low-speed ***,it is observed that the particle Stokes number(size)significantly affects both the strength of these vortices and the streaky structure exhibited by ***,a quantitative analysis of particle behavior in the near-wall region and the formation of elongated particle lines was carried *** involved examining the average fluid streamwise velocity fluctuations at particle locations,average particle concentration,and the normal velocity of particles for each set of particle Stokes *** investigation reveals the intricate interplay between particles and near-wall structures and the significant influence of particles Stokes *** study contributes to a deeper understanding of turbulent particle-laden channel flow dynamics.

关键词： Turbulent channel flow particle-laden flow direct numerical simulation(DNS) Eulerian-Lagrangian vortex identification turbulence coherent structures liutex

Copper-based nanomaterials as peroxidase candidates for intelligent colorimetric detection and antibacterial applications

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Particuology 2024年第1期84卷 126-135页

作者： Yanyan Huang Huimin Zhong Cong Jiang Jiahui Yang Jingwen Zhang Fei Zhao chaoqun liu College of Light Industry and Food Engineering Nanjing Forestry UniversityNanjing210037China College of Pharmacy Institutes of Environment and MedicineHenan UniversityKaifeng475004China

With natural polyphenol compound tannic acid(TA)as the ingredient,copper tannate(CuTA)nanolayer material was formed by self-assembly under the conditions of heating and copper *** ion and tannic acid could coordinate to form Cu-O-C structure which was similar to the Fe-N-C structure of natural heme *** addition,the obtained CuTA nanomaterial possessed excellent peroxidase-like catalytic activity and *** on this excellent enzymatic activity,CuTA nanomaterials could be used for colorimetric detection of hydrogen peroxide with a smartphone and decomposition of organic *** on the structural characteristics and catalytic activity,the copper tannate nanozymes could also serve as potential antibacterial reagents to effectively inhibit the growth of gram-negative and positive bacteria in a low hydrogen peroxide *** work may promote the exploration of novel peroxidase mimetics and broaden the applications of nanozymes.

关键词： Nanozyme Colorimetric detection Smartphone Antibacteria

Bacterial microcompartment-mimicking Pickering emulsion droplets for detoxification of chemical threats under sweet conditions

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Science China Chemistry 2024年第9期67卷 3039-3049页

作者： Xiao Xu Wenqi Xie Ting Wu Chen Chen Xiaoning Chen Yuheng Yang Hao Lian Hao Chen Xiaofeng Cheng Zhitong Chen Guojun Chen chaoqun liu Lanlan Chen Yu He Zhaowei Chen Bernard P.Binks Huanghao Yang New Cornerstone Science Laboratory MOE Key Laboratory for Analytical Science of Food Safety and BiologyCollege of ChemistryFuzhou UniversityFuzhou 350002China Institute of Biomedical and Health Engineering Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China Department of Biomedical Engineering and the Rosalind&Morris Goodman Cancer Research Institute McGill UniversityMontreal QC H3A 1A3Canada School of Pharmacy Henan UniversityKaifeng 475004China Department of Chemistry University of HullHull HU67RXUK

Chemical warfare agents represent a severe threat to mankind and their efficient decontamination is a global ***,traditional disposal strategies have limitations,including high energy consumption,use of aggressive reagents and generation of toxic ***,inspired by the compartmentalized architecture and detoxification mechanism of bacterial microcompartments,we constructed oil-in-water Pickering emulsion droplets stabilized by hydrogen-bonded organic framework immobilized cascade enzymes for decontaminating mustard gas simulant(2-chloroethyl ethyl sulfide,CEES)under sweet *** exemplified droplet systems were developed with two-enzyme(glucose oxidase/chloroperoxidase)and threeenzyme(invertase/glucose oxidase/chloroperoxidase)cascades,both achieving over 6-fold enhancement in decontamination efficiency compared with free enzymes and>99% selectivity towards non-toxic *** found that the favored mass transfer of sugars and CEES from their respective phases to approach the cascade enzymes located at the droplet surface and the facilitated substrate channeling between proximally immobilized enzymes were key factors in augmenting the decontamination *** importantly,the robustness of immobilized enzymes enabled easy reproduction of both the droplet formation and detoxification performance over 10 cycles,following long-term storage and in far-field locations.

关键词： Pickering emulsion biomimetics chemical warfare agent bacterial microcompartment biocatalysis

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重频大电流下金属化膜脉冲电容器温升累积效应研究

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中国电机工程学报 2024年第5期44卷 2068-2076,I0035页

作者：李长云刘超群于永进山东科技大学电气与自动化工程学院山东省青岛市266590

电磁发射技术中通常要求脉冲功率电源具有数十千安幅值、数毫秒脉宽的脉冲电流,并且具备重复频率连续发射能力。金属化薄膜电容器因其储能密度高、使用寿命长而被广泛应用于脉冲电源系统。根据脉冲电容器的结构及脉冲电源的工作模式,该... 详细信息

电磁发射技术中通常要求脉冲功率电源具有数十千安幅值、数毫秒脉宽的脉冲电流,并且具备重复频率连续发射能力。金属化薄膜电容器因其储能密度高、使用寿命长而被广泛应用于脉冲电源系统。根据脉冲电容器的结构及脉冲电源的工作模式,该文首先建立脉冲电容器的发热及散热模型;然后,在多物理场仿真软件COMSOL Multiphysics 5.6中建立瞬态温度场模型,并结合现有实验结果验证模型有效性,进而讨论重复频率脉冲放电应用中金属化膜脉冲电容器内部温升的累积现象。结果表明:在脉冲放电峰值1 kA、环境温度15℃、金属膜厚4 nm条件下,以12次/min的重复频率、30 s时间间隔连续工作10次后,脉冲电容器芯子最大温升为22.9℃。在此基础上,仿真分析环境温度、重复频率、脉冲电流峰值、电极厚度四方面因素对脉冲电容器温升的影响。该模型给出重频大电流下脉冲电容器内部瞬态发热规律,可为脉冲电容器合理运行和优化设计提供参考。

关键词：电磁发射脉冲电容器重复频率有限元累积效应

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多尺度纤维对水泥基复合材料性能的影响

深圳大学学报（理工版） 2024年第2期41卷 145-151页

作者：卫颖颖刘超群罗林陕西铁路工程职业技术学院测绘与检测学院陕西渭南714099 四川自力建筑勘测设计有限公司四川泸州646005

为准确掌握多尺度纤维对水泥基复合材料的性能影响规律,以碳酸钙晶须(calcium carbonate whisker,CW)纤维、钢纤维及聚乙烯醇(polyvinyl alcohol,PVA)纤维为基础,构建多尺度纤维水泥基复合材料,并在不同配合比条件下,通过流动性试验、... 详细信息

为准确掌握多尺度纤维对水泥基复合材料的性能影响规律,以碳酸钙晶须(calcium carbonate whisker,CW)纤维、钢纤维及聚乙烯醇(polyvinyl alcohol,PVA)纤维为基础,构建多尺度纤维水泥基复合材料,并在不同配合比条件下,通过流动性试验、单轴受压试验、三点弯曲缺口试验和叠加试验(overlay test,OT),研究多尺度纤维对水泥基复合材料力学性能、断裂性能及疲劳性能的影响规律.结果表明,多尺度纤维对水泥基复合材料的力学性能及断裂性能均具显著影响,在力学性能方面,多尺度纤维能较大程度上减弱水泥基复合材料的流动扩展度,并提高轴心抗压强度和弯曲抗拉强度;在断裂性能研究方面,单掺纤维组和混杂纤维组均能不同程度上提高水泥基复合材料的断裂性能.其中,对失稳断裂韧度和黏聚韧度的提升规律较为一致,在断裂性能指标的提升幅度上,黏聚韧度>失稳断裂韧度>起裂断裂韧度;CW纤维、钢纤维及PVA纤维的体积分数分别为0.50%、0.75%和0.25%时,水泥基复合材料的疲劳性能相对最优.研究成果可为水泥基复合材料的工程应用提供理论依据.

关键词：复合材料多尺度纤维试验设计力学性能断裂性能疲劳性能

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利用加速度计数据在轨标定重力卫星质心偏差

中山大学学报（自然科学版）（中英文） 2024年第2期63卷 123-130页

作者：刘超群谷德峰黄志勇王傲明刘道平中山大学人工智能学院广东珠海519082 “天琴计划”教育部重点实验室/天琴前沿科学中心/国家航天局引力波研究中心广东珠海519082 地理信息工程国家重点实验室陕西西安710054

针对重力卫星质心偏差在轨标定的问题,提出了一种仅使用加速度计数据进行质心在轨标定的方法:以1A级加速度计数据作为输入,采用Butterworth滤波去除数据中的噪声,提取质心标定机动产生的线性加速度和角加速度信号,最后结合最小二乘原理... 详细信息

针对重力卫星质心偏差在轨标定的问题,提出了一种仅使用加速度计数据进行质心在轨标定的方法:以1A级加速度计数据作为输入,采用Butterworth滤波去除数据中的噪声,提取质心标定机动产生的线性加速度和角加速度信号,最后结合最小二乘原理对质心偏差进行标定。利用GRACE-FO C星的加速度计数据对提出的质心标定方法进行验证,估计了C星发射至今的质心偏差。结果显示,三轴的标定精度均优于10μm,与利用姿态数据计算的质心偏差在三轴方向上的互对比差异(RMS)为[9.6,9.3,7.9]μm,与喷气推进实验室(JPL)公布结果的RMS为[7.4,3.8,4.7]μm。与传统方法不同,由于仅使用了加速度计测量数据,该方法可用于卫星姿态缺失情况下的质心在轨标定。

关键词： GRACE-FO 重力卫星加速度计质心标定

New ideas on governing equations of fluid dynamics

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Journal of Hydrodynamics 2021年第4期33卷 861-866页

作者： chaoqun liu Department of Mathematics University of Texas at ArlingtonArlingtonTexas76019USA

Classical fluid kinematics or Cauchy-Stokes decomposition mistreated vorticity as fluid rotation and mixed flow stretching with *** fluid dynamics or Navier-Stokes(N-S)equations are based on the classical kinematics and treated vorticity as null in contribution of forces and mixed the stretching force with the shearing force,which is not consistent with the Galilean invariancy.N-S equations also neglect the flow *** is believed that N-S equations may work for incompressible and laminar flow but are not satisfied for turbulent flow and compressible flow especially for high-speed *** on liutex,new fluid kinematics has been established by liu in 2021,which gives a liutex-based principal coordinate system and a new principal decomposition in that system,which has been transferred back to the original Cartesian coordinate *** principal decomposition of velocity gradient tensor has four parts which are called rotation,stretching,anti-symmetric shearing and symmetric *** forces are derived according to the four parts of the velocity gradient *** to the new fluid kinematics,it is reported in this letter that based on the principal decomposition,a new relation between the velocity gradient tensor and stress-rate tensor has been established to form a new fluid dynamics equation to govern fluid *** new governing equation may be applicable to both laminar flow and turbulent flow,and both incompressible flow and compressible flow including high-speed flow for reasonable results with reasonable *** numerical experiment is needed to verify.

关键词： New fluid kinematics strain stress Newton’s law Navier-Stokes new fluid dynamics

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New fluid kinematics

Journal of Hydrodynamics 2021年第3期33卷 395-399页

作者： chaoqun liu Department of Mathematics University of Texas at ArlingtonArlingtonTexas76019USA

Fluid kinematics describes the fluid motion without consideration of any *** fluid kinematics adopts Helmholtz velocity decomposition,which is equivalent to Cauchy-Stokes(CS)velocity gradient tensor *** decomposes the velocity gradient tensor into a strain-rate(symmetric)tensor and a vorticity(anti-symmetric)***,several questions arise:(1)since vorticity cannot represent fluid rotation,the vorticity tensor is a mixture of vorticity shear and rigid rotation,(2)since the strain-rate tensor cannot represent fluid shear,the strain-rate tensor is a mixture of stretching and shear,(3)the stretching and shear in the CS decomposition are dependent on the selection of coordinate system and are therefore not Galilean *** the other hand,liutex is a new physical quantity to represent the rigid fluid rotation and a principal coordinate system can be set up based on liutex.A principal decomposition of the velocity gradient tensor,or the rotation-stretching-shear decomposition,can be easily carried out in the principal coordinate system with a clear physical meaning,which represents the rigid rotation,stretching(compression)and shear(symmetric and anti-symmetric shear).In the principal decomposition,all elements in three sub-tensors are Galilean invariant and,therefore,the principal decomposition is unique,Galilean invariant and independent of coordinate *** principal decomposition is then transformed back to the original xyz coordinate *** liutex-based principal decomposition creates the new fluid kinematics which is ready for building up new fluid *** fluid kinematics is the foundation of the fluid dynamics,the new fluid kinematics could replace the classical fluid kinematics,Helmholtz or CS decomposition,and open a new gate to develop new fluid dynamics especially for vortex science and turbulence research.

关键词： New fluid kinematics Helmholtz Cauchy Stokes liutex principal decomposition

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“全过程人民民主”的政治哲学维度

毛泽东思想研究 2024年第2期 9-15页

作者：刘超群南开大学哲学院天津300350

全过程人民民主是发展的、和现实紧密结合的、面向中国式现代化这一时代主题的政治哲学,是中国共产党领导人民在理解追求人类文明新形态、推动构建人类命运共同体、实现中华民族伟大复兴的过程中不断探索的制度建构和政治实践,是对以西... 详细信息

全过程人民民主是发展的、和现实紧密结合的、面向中国式现代化这一时代主题的政治哲学,是中国共产党领导人民在理解追求人类文明新形态、推动构建人类命运共同体、实现中华民族伟大复兴的过程中不断探索的制度建构和政治实践,是对以西方民主建构逻辑为中心的政治哲学思维方式的论域突破和范式创新。全过程人民民主基于人民主体立场的伦理思维,遵循唯物辩证方法的过程思维,贯彻唯物史观观点的实践思维,蕴含了鲜明的马克思主义立场观点方法。全过程人民民主铸牢了中华民族共同体意识,推动了中国特色社会主义政治文明发展,彰显了文明互鉴的全球视野,为不断促进人的全面而自由发展以及探索实践中国式现代化道路开拓了更为广阔的发展空间。

关键词：全过程民主中国式现代化政治哲学